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Case Studies

Case Studies (327)

Invasive floating plant dominance to invasive submerged plant dominance in South African freshwater systems

Main Contributors:

Emily Strange

Other Contributors:

Julie Coetzee, Julie Coetzee

Summary

As naturally occurring large bodies of freshwater are rare in South Africa there are numerous man-made dams and lakes, these systems are highly vulnerable to colonization from non-native invasive plants due to multiple factors. Firstly, there is a lack of native aquatic plant species to occupy the water column and compete for resources. Secondly they are often eutrophic systems, caused by anthropogenic activity such as intensive agriculture and improper human waste disposal, and nutrient loading is a known driver of invasive plants. Also, it has been argued that the intrinsic nature of freshwater systems leads them to be disproportionately affected by non native invasive species when compared with terrestrial systems (Moorhouse and McDonald 2015).

This combination has lead to a long battle against floating invasive plants that dominate many of South Africa’s freshwater resources.. These plants form dense mats on the waters surface, restricting light to other species, damaging hydroelectric equipment, limiting water quality and reducing biodiversity. They can also play host to vectors of disease such as malari and schistosomiasis (Mack and Smith, 2011). The implementation of classical biological control programs, using the natural enemies of the invasive plants, has proven to be a huge success when controlling detrimental invasive plants such as water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes L. (Araceae)), Kariba weed (Salvinia molesta D.S. Mitchell (Salviniaceae)), parrots feather (Myriophyllum aquaticum (Vellozo Conceição) Verdcourt) and red water fern (Azolla filiculoides Lamarck (Azollaceae)) (Hill 2002)

The host-specific biological control agents (BCAs), typically insects and mites, have coevolved with the plants in their natural range and are intentionally introduced to manage invasive plant populations.

The overall aim of this is to induce a regime shift into a functioning system with high native biodiversity and freshwater access. However, we propose that whilst the BCAs do lead to a dramatic reduction in the biomass and health of the floating plant, it can also act as a catalyst inducing a shift into a second degraded stable regime. This second regime is one that is dominated by submerged invasive plants. The establishment of the BCAs on the floating plants can lead to a rapid plant population crash and the nutrients they were locking up are released. At the same time submerged light levels are restored in the water column, enabling a new suite of submerged invasive plants to flourish. The increase in space, light and nutrients promotes the submerged plant growth and as they continue to photosynthesize the levels of dissolved oxygen in the water rise. This improvement in water quality, alongside a limited number of native submerged plants to compete with, helps to establish and maintain this second stable regime (invasive submerged plant dominance). These rooted plants can alter water flow, turbidity and sediment stabilization (Yarrow et al. 2009). They can also degrade water quality and biodiversity, restrict access to freshwater and damage hydro-electrical equipment.

Type of regime shift

Ecosystem type

  • Freshwater lakes & rivers

Land uses

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots, dairies)
  • Extensive livestock production (natural rangelands)
  • Conservation
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Africa

Region

  • South Africa

Countries

  • South Africa

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Charles H & Dukes JS. 2007. Impacts of invasive species on ecosystem services. Biological Invasions; Ecological Studies 193.
  2. Coetzee et al. 2011 Prospects for the biological control of submerged macrophytes in South Africa. African Entomology : Biological control of invasive alien plants in South Africa (1999 - 2010): Special Issue 2.
  3. Coetzee J & Hill MP. 2012. The role of eutrophication in the biological control of water hyacinth, Eichhornia crassipes, in South Africa. BioControl 57, 247-261.
  4. Hill MP. 2002. The impact and control of alien aquatic vegetation in South African aquatic ecosystems. African Journal of Aquatic Science 28, 19-24
  5. Mack RN & Smith MC. 2011. Invasive plants as catylsts for the spread of human parasites. NeoBiota 9, 13-29.
  6. Martin GD & Coetzee JA. 2011. Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa. Water SA [online] 37, pp. 371-380. ISSN 0378-4738
  7. McConnachie J, de Wit, MP, Hill MP, Byrne MJ. Economic evaluation of the successful biological control of Azolla filiculoides in South Africa, Biological Control, 28 (1) ISSN 1049-9644.
  8. Moorhouse and McDonald. 2015. Are invasives worse in freshwater than terrestrial ecosystems? Wiley Periodicals
  9. Yarrow M, Marin VH, Finlayson M, Tironi A, Delgado LE & Fishcher F. 2009. The ecology of Egeria densa Planchon (Liliopsida: Alismatales): A wetland ecosystem engineer? Revista Chilena de Historia Natural 82, 299-313.

Citation

Emily Strange, Julie Coetzee, Julie Coetzee. Invasive floating plant dominance to invasive submerged plant dominance in South African freshwater systems. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-08-27 10:46:02 GMT.

Megadiverse fynbos shrublands to invasive wattle tree monoculture.

Main Contributors:

Ross Shackleton

Other Contributors:

Reinette (Oonsie) Biggs, Dave Richardson

Summary

The southwestern tip of Africa is home to the Fynbos biome (Cape Floristic Region), which is characterised by highly diverse plant groups, many of which are endemic and occur nowhere else in the world. Numerous species of Australian acacia (wattles) were introduced to South Africa for multiple reasons, including sand/dune stabilisation, ornamental purposes, and forestry. Many species have subsequently naturalised and some are widespread invaders. The Australian wattles have filled an empty niche (trees in a virtually treeless system) causing a regime shift. This shift has induced many negative impacts to the social-ecological system in the area. These include alterations to fire and hydrological systems, changes in soil nutrient cycles, biodiversity loss, and negative impacts on local livelihoods and human well-being through loss of grazing, water supply, ecotourism and increased exposure to natural hazards. Ongoing management interventions include mechanical and chemical control and the use of biological control agents.

Type of regime shift

  • Introduction of aline species (Biological invasions)

Ecosystem type

  • Mediterranean shrubs (egFynbos)

Land uses

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Extensive livestock production (natural rangelands)
  • Timber production
  • Conservation
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Africa

Region

  • Western Cape, South Africa

Countries

  • South Africa

Locate with Google Map

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Allsopp N. 2014. Fynbos: ecology, evolution and conservation of a megadiverse region. Oxford University Press, USA.
  2. Blackburn T, et al. 2011. A proposed unified framework for biological invasions. Trends in Ecology and Evolution, 26, 333-339.
  3. Charles H, and Dukes JS. 2008. Impacts of invasive species on ecosystem services. In: Biological Invasions, Nentwig, W. (ed). Springer, Berlin. pp 217-237.
  4. Gaertner M, et al. 2014. Invasive plants as drivers of regime shifts: identifying high-priority invaders that alter feedback relationships. Diversity and Distributions 20,733-744.
  5. Le Maitre D, et al 1996. Invasive plants and water resources in the Western Cape province, South Africa; Modeling and the consequences of a lack of management. Journal of Applied Ecology 33, 161-172.
  6. Le Maitre D, et al. 2011 Impacts of invasive Australian acacias: implications for management and restoration. Diversity and Distributions 17, 1015-1029.
  7. Richardson DM, et al. 1989. Reductions in plant species richness under stands of alien trees and shrubs in the fynbos biome. South African Forestry Journal 149,1-8.
  8. Shackleton CM, et al 2007. Assessing the effects of alien species on rural livelihoods; case examples and a framework from South Africa. Human Ecology 35, 113-127.
  9. Turpie J, et al. 2003. Economic value of terrestrial and marine biodiversity in the Cape Floristic Region: implications for defining effective and socially optimal conservation strategies. Biological Conservation 122, 233-251.
  10. van Wilgen BW, et al 2012. An assessment of the effectiveness of a large national-scale invasive alien plant control strategy in South Africa. Biological Conservation 148, 28-38.
  11. van Wilgen BW, et al. 2011. National-scale strategic approaches for managing introduced plants: Insights from Australian acacias in South Africa. Diversity and Distributions 17, 1060-1075.
  12. Wilson JRU, et al. 2013. A new national unite for invasive species detection, assessment and eradication planning. South African Journal of Science 109, 1-13.

Citation

Ross Shackleton, Reinette (Oonsie) Biggs, Dave Richardson. Megadiverse fynbos shrublands to invasive wattle tree monoculture. . In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-07-25 05:17:24 GMT.
Sunday, 05 March 2017 16:28

Mediterranean Basin

Written by Juli Pausas

Mediterranean Basin

Main Contributors:

Juli Pausas

Other Contributors:

Summary

In the European region of the Mediterranea Basin there was an abrupt fire regime shift in such a way that fires increased in annual frequency (doubled) and area burned (by about an order of magnitude). The main driver of this shift was the increase in fuel amount and continuity due to rural depopulation (vegetation and fuel build-up after farm abandonment) suggesting that fires were fuel-limited previous to the shift. Climatic conditions are poorly related to wildfire activity during the pre-shift period and strongly related during the to post-shift period, suggesting that fires are currently less fuel limited and more drought-driven than before. Thus, the fire regime shift implies also a shift in the main driver for fire activity. This shift was dated in the 1970s in Spain but this may varies in other countries.




Type of regime shift

  • Fire regime shift

Ecosystem type

  • Mediterranean shrubs (egFynbos)

Land uses

  • Small-scale subsistence crop cultivation

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Europe

Region

  • Mediterranean Basin

Countries

  • Spain
  • Greece

Locate with Google Map

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226.
  2. Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. http://dx.doi.org/10.1007/s10584-011-0060-6

Citation

Juli Pausas. Mediterranean Basin. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-03-09 16:22:33 GMT.
Friday, 08 January 2016 16:52

Vegetation regime shifts in Yamal-Nenets

Written by Hanna Ahlström

Vegetation regime shifts in Yamal-Nenets

Main Contributors:

Hanna Ahlström, Jonas Gren, Ashley Perl, Fernando Remolina, Fernando Remolina, Ashley Perl, Jonas Gren

Other Contributors:

Summary

The Yamal-Nenets social-ecological system comprises about 5000 nomadic reindeer herders and 300 000 semi-domestic reindeers, moving with the seasons in 21 different brigades from the southern tree limit up north, across the Arctic tundra. Shrub encroachment has been observed during the last three decades, but has been controlled by reindeer grazing. These changes have produced two regime states: shrubland without reindeer herding, and open land with reindeer herding. The first regime is mainly caused by temperature increase, which has produced warmer winters, summers and extended growing seasons. These temperature changes have altered the controlling feedbacks of the tundra, such as slow growth of shrubs, microbial activity, and decomposition litter rates. This regime is hence seen as the undesirable regime for the Yamal-Nenets social-ecological system.

Type of regime shift

Ecosystem type

  • Grasslands
  • Tundra
  • Polar
  • Agro-ecosystems

Land uses

  • Extensive livestock production (natural rangelands)

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Asia
  • Europe

Region

  • Yamal Peninsula, Northwest Siberia

Countries

  • Russia

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Aune, S., Hofgaard, A., & Söderström, L. 2011. Contrasting climate- and land-use-driven tree encroachment patterns of subarctic tundra in northern Norway and the Kola. Canadian Journal of Forest Research, 41(3), 437–449.
  2. Bråthen, K. A., Ims, R. a., Yoccoz, N. G., Fauchald, P., Tveraa, T., & Hausner, V. H. 2007. Induced Shift in Ecosystem Productivity? Extensive Scale Effects of Abundant Large Herbivores. Ecosystems, 10(5), 773–789.
  3. Couture, T., and Gagnon, Y. 2010. An analysis of feed-in tariff remuneration models: Implications for renewable energy investment. Energy policy 38 (10), 955-965. Degteva, A., & Nellemann, C. (2013). Nenets migration in the landscape: impacts of industrial development in Yamal peninsula, Russia. Pastoralism: Research, Policy and Practice, 3(1), 15.
  4. Forbes, B. C., Stammler, F., Kumpula, T., Meschtyb, N., Pajunen, A., & Kaarlejärvi, E. 2009. High resilience in the Yamal-Nenets social-ecological system, West Siberian Arctic, Russia. Proceedings of the National Academy of Sciences of the United States of America, 106(52), 22041–8.
  5. Golovatin, M. G., Morozova, L. M., & Ektova, S. N. 2012. Effect of reindeer overgrazing on vegetation and animals of tundra ecosystems of the Yamal peninsula, Czech Polar reports, 2(12), 80–91
  6. Grace, J., Berninger, F., & Nagy, L. 2002. Impacts of Climate Change on the Tree Line. Annals of Botany, 90(4), 537–544.
  7. Henden, J.-A., Yoccoz, N. G., Ims, R. a, & Langeland, K. 2013. How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra. PloS one, 8(5),1-10.
  8. Kullman, L. 2002. Rapid recent range-margin rise of tree and shrub species in the Swedish Scandes. Journal of Ecology, 90(1), 68–77.
  9. Kumpula, T., Forbes, B. C., Stammler, F., & Meschtyb, N. 2012. Dynamics of a Coupled System: Multi-Resolution Remote Sensing in Assessing Social-Ecological Responses during 25 Years of Gas Field Development in Arctic Russia. Remote Sensing, 4(12), 1046–1068.
  10. Kumpula, T., Pajunen, A., Kaarlejärvi, E., Forbes, B. C., & Stammler, F. 2011. Land use and land cover change in Arctic Russia: Ecological and social implications of industrial development. Global Environmental Change, 21(2), 550–562.
  11. Macias-Fauria M, Forbes BC, Zetterberg P, Kumpula T. 2012. Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems. Nature Climate Change 2, 613–618.
  12. Myers-Smith, I. H. 2007. Shrub Line Advance in Alpine Tundra of the Kluane Region: Mechanisms of Expansion and Ecosystem Impacts. Arctic, 60(4), 447-451.
  13. Olofsson, J., Oksanen, L., Callaghan, T., Hulme, P. E., Oksanen, T., & Suominen, O. 2009. Herbivores inhibit climate-driven shrub expansion on the tundra. Global Change Biology, 15(11), 2681–2693.
  14. Strum, M., Douglas, T., Racine, C., & Liston, G. E. 2005. Chagning snow and shrub conditions affect albedo with global implications. Journal of Geophysical Research, 110, 2156-2202.
  15. Sturm, M., Schimel, J., Michaelson, G., Welker, J. M., Oberbauer, S. F., Liston, G. E., … Romanovsky, V. E. 2005. Winter Biological Processes Could Help Convert Arctic Tundra to Shrubland. BioScience, 55(1), 17-26.
  16. Tape, K., Sturm, M., & Racine, C. 2006. The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Global Change Biology, 12(4), 686–702.
  17. Wal, V. D. R., 2006. Do herbivores cause habitat degradation or vegetation state transition ? Evidence from the tundra. Oikos, 114:1, 177–186.
  18. Walker, D. A., Forbes, B. C., Leibman, M. O., Epstein, H. E., Bhatt, U. S., Comiso, J. C., … Yu, Q. 2011. Eurasian Arctic Land Cover and Land Use in a Changing Climate. (G. Gutman & A. Reissell, Eds.), 207–236.
  19. Walker, M. D., C. Wahren, H., Hollister, R. D., Henry, G. H. R., Ahlquist, L. E., Alatalo, J., … Wookey, P. A. 2006. Plant community responses to experimental warming across the tundra biome PNAS, 103(5), 1342-1346.
  20. Yu, Q., Epstein, H. E., Walker, D. a, Frost, G. V, & Forbes, B. C. 2011. Modeling dynamics of tundra plant communities on the Yamal Peninsula, Russia, in response to climate change and grazing pressure. Environmental Research Letters, 6(4),1-12.
  21. Zeng, H., Jia, G., & Forbes, B. C. 2013. Shifts in Arctic phenology in response to climate and anthropogenic factors as detected from multiple satellite time series. Env. Rev. Lett., 8, 1–12.
  22. Zimov, A. S. A., Chuprynin, V. I., Oreshko, A. P., Iii, F. S. C., & Reynolds, J. F. 1995. Steppe-Tundra Transition : A Herbivore-Driven Biome Shift at the End of the Pleistocene American Naturalist 146(5), 765–794.

Citation

Hanna Ahlström, Jonas Gren, Ashley Perl, Fernando Remolina, Fernando Remolina, Ashley Perl, Jonas Gren. Vegetation regime shifts in Yamal-Nenets. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-08 10:45:18 GMT.

Collapse of Newfoundland cod fisheries, Northwest Atlantic

Main Contributors:

Roweena Patel, Kate Williman, Viveca Mellegard, Philipp Siegel, Kate Williman, Viveca Mellegard, Philipp Siegel

Other Contributors:

Reinette (Oonsie) Biggs, Juan Carlos Rocha

Summary

The Newfoundland cod fishery is a social-ecological system that is centered upon Arctic cod, Gadus morhua populations in the waters off Newfoundland and Labrador in the Northwest Atlantic. High fishing pressure, along with regional climatic variability that delivered colder water to the Northwest Atlantic ocean, disturbed the cod spawning grounds and led to a dramatic cod fishery collapse. Recovery in the fishery has been minimal and very slow, partly because cod population growth will take time to replenish the amount of stock that was lost. This regime shift has impacted ecosystem services by reducing the food source both at the local and the global scale. There has also been a loss of income from cod fishing at the local scale that affects human wellbeing among Newfoundland fishers and the communities relying directly and indirectly on the fishing industry. Actions taken to restore the cod regime shift includes banning of the commercial fisheries in the Northwest Atlantic, tighter regulations and dock-side monitoring programs.

Type of regime shift

Ecosystem type

  • Marine & coastal

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • North America
  • Atlantic Ocean

Region

  • Northern North Atlantic

Countries

  • Canada

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Arnason, R., Sandal, L. K., Steinshamn, S. I., & Vestergaard, N. (2004). Optimal Feedback Controls: Comparative Evaluation of the Cod Fisheries in Denmark, Iceland, and Norway. American Journal of Agricultural Economics, 86(2): 531-542.
  2. Bavington, D. (2010). From hunting fish to managing populations: fisheries science and the destruction of Newfoundland cod fisheries. Science as Culture, 19(4), 509-528.
  3. Berec, L., Angulo, E., & Courchamp, F. (2007). Multiple Allee effects and population management. Trends in Ecology and Evolution, 22(4): 185-191.
  4. Caddy, J.F., and Agnew, D.J., (2005). An overview of recent global experiences with recovery plans for depleted marine resources and suggested guidelines for recovery planning. Reviews in Fish Biology and Fisheries 14: 43–112.
  5. Canada-Newfoundland and Labrador. (2003). A strategy for the recovery and management of cod stocks in Newfoundland and Labrador. Action Team for Cod Recovery Report, Department of Fisheries and Oceans, Department of Fisheries and Aquaculture, St. John’s, NL, Canada.
  6. Canada-Quebec. (2005). Towards a recovery strategy for Gulf of St. Lawrence cod stocks. Canada-Quebec Cod Action Team Cod Rebuilding Strategy. Department of Fisheries and Oceans, Moncton, Quebec, Canada.
  7. Clark, R.A., Fox, C. J.,Viner, D., Livermore, M. (2003). North Sea cod and climate change – modelling the effects of temperature on population dynamics. Global Change Biology, 9(11): 1669–1680.
  8. Cohen, J., & Barlow, M. (2005). The NAO, the AO, and Global Warming: How Closely Related?. Journal of Climate, 18: 4498-4513.
  9. Colbourne, E., Craig, J., Fitzpatrick, C., Senciall, D., Stead, P., Bailey, W., & Department of Fisheries and Oceans, Ottawa, ON(Canada); Canadian Science Advisory Secretariat, Ottawa, ON(Canada). (2011). An assessment of the physical oceanographic environment on the Newfoundland and Labrador Shelf during 2010 (No. 2011/089). DFO, Ottawa, ON(Canada).
  10. Cox, K. (1994). Why the cold killed the cod. [ Toronto] Globe and Mail, 31 January.
  11. DFO. (2010). Economic overview of the groundfish industry. Economic analysis and statistics, policy sector. Presentation at the Fisheries Resource Conservation Council Meeting. Feb 17–20, 2010, Montreal, Quebec, Canada.
  12. Drinkwater, K. F. (2002). A review of the role of climate variability in the decline of northern cod. Fisheries in a Changing Climate, 113-130.
  13. Drinkwater, K. F. (2005). The response of Atlantic cod (Gadus morhua) to future climate change. ICES Journal of Marine Science: Journal du Conseil, 62(7), 1327-1337.
  14. Drinkwater, K. F. (2006). The regime shift of the 1920s and 1930s in the North Atlantic. Progress in Oceanography, 68(2), 134-151.
  15. Dutil, J.-D., & Brander, K. (2003). Comparing productivity of North Atlantic cod (Gadus morhua) stocks and limits to growth production. Fisheries Oceanography, 12(4/5): 502–512.
  16. Eide, A., Heen, K., Armstrong, C., Flaaten, O., & Vasiliev, A. (2013). Challenges and Successes in the Management of a Shared Fish Stock–The Case of the Russian–Norwegian Barents Sea Cod Fishery. Acta Borealia,30(1), 1-20.
  17. Fromentin,J.-M., & Planque, B. (1996). Calanus and environment in the eastern North Atlantic. II. Influence of the North Atlantic Oscillation on C. finmarchicus and C. helgolandicus. Marine Ecology Progress Series, 134: 111-118.
  18. Greene, C. H., & Pershing, A. J (2000). The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: basin-scale forcing associated with the North Atlantic Oscillation. Journal of Marine Science, 57: 1536–1544.
  19. Greene, C. H., Pershing, A. J., Cronin, T. M., & Ceci, N. (2008). Arctic climate change and its impacts on the ecology of the North Atlantic. Ecology, 89(11): 24-38.
  20. Haedrich, R. L., & Hamilton, L. C. (2000). The fall and future of Newfoundland's cod fishery. Society & Natural Resources, 13(4), 359-372.
  21. Hamilton, L. (2010). Footprints: Demographic effects of outmigration. Migration in the Circumpolar North: Issues and Contexts. L. Husky and C. Southcott (Eds). Edmonton, Alberta: Canadian Circumpolar Institute, 1-14.
  22. Hamilton, L. C., & Butler, M. J. (2001). Outport adaptations: Social indicators through Newfoundland's cod crisis. Human Ecology Review, 8(2), 1-11.
  23. Hátún, H. , Payne, M.R., Beaugrand, G., Reid, P.C., Sandø, A.B., Drange, H., Hansen, B., Jacobsen, J.A, & Bloch, D. (2009). Large bio-geographical shifts in the north-eastern Atlantic Ocean: From the subpolar gyre, via plankton, to blue whiting and pilot whales. Progress in Oceanography, 80: 149–162.
  24. Howard, M. (2003). When fishing grounds are closed: Developing alternative livelihoods for fishing communities. Secretariat for the Pacific Community Women in Fisheries Information Bulletin, 13, 19-22.
  25. Khan, A., & Chuenpagdee, R. (2013). An Interactive Governance and Fish Chain Approach to Fisheries Rebuilding: A Case Study of the Northern Gulf Cod in Eastern Canada. Ambio, 1-14.
  26. Krohn, M., Reidy, S., & Kerr, S. (1997). Bioenergetic analysis of the effects of temperature and prey availability on growth and condition of northern cod (Gadus morhua). Canadian Journal of Fisheries and Aquatic Sciences, 54(1): 113-121.
  27. Lilly, G. R., Nakken, O., & Brattey, J. (2013). A review of the contributions of fisheries and climate variability to contrasting dynamics in two Arcto-boreal Atlantic cod (Gadus morhua) stocks: persistent high productivity in the Barents Sea and collapse on the Newfoundland and Labrador Shelf. Progress in Oceanography.
  28. Mason, F. (2002). The Newfoundland Cod Stock Collapse: A Review and Analysis of Social Factors. Electronic Green Journal, 1(17), Article 2.
  29. McCay, B. J., & Finlayson, A. C., (1995). The political ecology of crisis and institutional change: the case of the northern cod. Annual Meeting of the American Anthropological Association, Washington, DC.
  30. Milich, L. (1999). Resource mismanagement versus sustainable livelihoods: The collapse of the Newfoundland cod fishery. Society & Natural Resources,12(7), 625-642.
  31. Morgan, M. J., DeBlois, E. M., & Rose, G. A. (1997). An observation on the reaction of Atlantic cod (Gadus morhua) in a spawning shoal to bottom trawling. Canadian Journal of Fisheries and Aquatic Sciences, 54(S1), 217-223.
  32. Myers, R. A., Hutchings, J. A., & Barrowman, N. J. (1996). Hypothesis for the decline of cod in the North Atlantic. Marine Ecology Progress Series, 138: 293-308.
  33. Myers, R. A., Hutchings, J. A., & Barrowman, N. J. (1997). Why do Fish Stocks Collapse? The Example of Cod in Atlantic Canada. Ecological Applications, 7(1): 91-106.
  34. Nafo.int. (2013). NAFO Fishery. [online] Available at: http://www.nafo.int/fisheries/frames/tac.html [Accessed: 1 Dec 2013].
  35. Rose, G. A. (2004). Reconciling overfishing and climate change with stock dynamics of Atlantic cod (Gadus morhua) over 500 years. Canadian Journal of Fisheries and Aquatic Sciences, 61, 1553–1557.
  36. Rose, G. A., DeYoung, B., Kulka, D. W., Goddard, S. V., & Fletcher, G. L. (2000). Distribution shifts and overfishing the northern cod (Gadus morhua): a view from the ocean. Canadian Journal of Fisheries and Aquatic Sciences,57(3), 644-663.
  37. Rose,G.A., deYoung, B., Kulka, D.W., Goddard, S.V., & Fletcher G.L. (2000). Distribution shifts and overfishing the northern cod (Gadus morhua): a view from the ocean. Canadian Journal of Fisheries and Aquatic Sciences, 57: 644–663.
  38. Schrank, William E. (2005). The Newfoundland fishery: ten years after the moratorium. Marine Policy 29.5: 407-420.
  39. Song, A.M., Chuenpagdee, R., and Jentoft, S. (2013). Values, images, and principles: What they represent and how they may improve fisheries governance. Marine Policy 40: 167–175.
  40. Sundby, S. (2000). Recruitment of Atlantic cod stocks in relation to temperature and advection of copepod populations. Sarsia, 85: 277-298.
  41. Vilhjalmsson, H. (1983). Biology, abundance estimates and managements of the Icelandic stock of capelin. Rit. Fiskideild. 3: 153-181.
  42. Worm, B., & Myers, R. A. (2003). Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs. Ecology, 84(1), 162-173.

Citation

Roweena Patel, Kate Williman, Viveca Mellegard, Philipp Siegel, Kate Williman, Viveca Mellegard, Philipp Siegel, Reinette (Oonsie) Biggs, Juan Carlos Rocha. Collapse of Newfoundland cod fisheries, Northwest Atlantic. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:18:06 GMT.
Monday, 08 June 2015 19:53

Arctic mobility

Written by Cláudia Florêncio

Arctic mobility

Main Contributors:

Tove Björklund, Cláudia Florêncio, Rawaf al Rawaf, Tove Björklund, Rawaf al Rawaf

Other Contributors:

Juan Carlos Rocha

Summary

Due to anthropogenic climate change and diminishing navigable ice, the Inuit’s mobility and available livelihoods are currently undergoing a regime shift. Inuit communities are increasingly relying on both wage employment and traditional subsistence harvesting, indicating we are probably witnessing the transition between these two livelihood regimes. The main drivers for this transition are anthropogenic climate change and increasing access to store-bought goods through trade and import. The necessity to secure access to food (either traditional or store-bought), and the erosion of traditional knowledge and shifting cultural norms are the key processes impacted by these drivers, as evidenced by the state of human well-being and ecosystem services in Inuit communities today.

Type of regime shift

Ecosystem type

  • Tundra
  • Polar

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Europe
  • North America
  • Arctic Ocean

Region

  • Arctic Region

Countries

  • Russia
  • Sweden
  • United States
  • Canada
  • Denmark
  • Finland

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Aporta, C. (2004) Routes, trails and tracks: trail breaking among the Inuit of Igloolik. Etudes/Inuit/Studies 28:9–38.
  2. Dicks, L. Arctic Climate Issues (2011) Changes in Arctic Snow, Water, Ice and Permafrost. Arctic Monitoring and Assessment Programme (AMAP).
  3. Ford, J. (2008) Vulnerability of Inuit food systems to food insecurity as a consequence of climate change: a case study from Igloolik, Nunavut. Regional Environmental Change. Springer.
  4. Ford, J. et al (2010) Climate change policy responses for Canada’s Inuit population: The importance of and opportunities for adaptation. Global Environmental Change 20, issue 1: p.177–191.
  5. Gearheard, S. Matumeak, W. Angutikjuaq, I. Maslanik, J.A. Huntington, H.J.L. Matumeak, D.G.T. Barry, R.G. (2006) It’s not that simple: comparison of sea ice environments, observed changes, and adaptations in Barrow Alaska, USA, and Clyde River, Nunavut, Canada. Ambio 35:203–211. doi:10.1579/0044-7447(2006)35 [203:INTSAC]2.0.CO;2
  6. Hastrup, K. (2009) Arctic hunters: climate variability and social flexibility. Chapter 12 in Hastrup, Kirsten. The Question of Resilience, Social Responses to Climate Change. The Royal Danish Academy of Science and Letters. 362p.
  7. Hastrup, K. (2013) The nomadic landscape: People in a changing Arctic environment. Geografisk Tidsskrift-Danish Journal of Geography, 109:2, 181-189, DOI: 10.1080/00167223.2009.10649606
  8. Hinzman, L.D. et al (2005) Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions. Climatic Change 72: 251–298 DOI: 10.1007/s10584-005-5352-2
  9. Huntington, H. & Fox, S. (2007) ACIA Secretariat and Cooperative Institute for Arctic Research University of Alaska Fairbanks, chapter 3, accessed on 2014-11-25 http://www.acia.uaf.edu/PDFs/ACIA_Science_Chapters_Final/ACIA_Ch03_Final.pdf
  10. ICC (2008) The Sea Ice is Our Highway - An Inuit Perspective on Transportation in the Arctic. A Contribution to the Arctic Marine Shipping Assessment. Inuit Circumpolar Council, Canada.
  11. ICC (2009) Circumpolar Inuit Health Summit. Yellowknife, Canada. Accessed on 2014-11-25 http://www.inuitcircumpolar.com/uploads/3/0/5/4/30542564/2009_healthsummitreport_final.pdf
  12. IPCC (2007) 4th assessment report, Climate change 2007: synthesis report. Accessed on 2014-11-20 http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf
  13. IPCC (2014) 5th assessment report 2013: AR5 Synthesis report. http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_LONGERREPORT.pdf
  14. Kral, M. (2003) Unikkaartuit: meanings of well-being, sadness, suicide, and change in two Inuit communities. Final Report to the National Health Research and Development Programs. Health Canada, Ottawa.
  15. Laidler et al (2009) Travelling and hunting in a changing Arctic: assessing Inuit vulnerability to sea ice change in Igloolik, Nunavut. Climatic Change 94:363–397 DOI 10.1007/s10584-008-9512-z
  16. Nuttall, M. Berkes, F. Forbes, B.C. Kofinas, G. Vlassova, T. & Wenzel, G. (2005) Hunting, Herding, Fishing, and Gathering: Indigenous Peoples and Renewable Resource Use in the Arctic. Pp. 649-690 in: Arctic Climate Impact Assessment. Cambridge, Cambridge University Press.
  17. Sørensen, M. (2010) Inuit landscape use and responses to climate change in the Wollaston Forland—Clavering Ø region, Northeast Greenland. Geografisk Tidsskrift-Danish Journal of Geography 110:155–174.
  18. Takano, T. (2004) Connections with the land: land skills courses in Igloolik, Nunavut. Ethnography 6:463–486.
  19. UNESCO (2009) Climate Change and Arctic Sustainable Development: scientific, social, cultural and educational challenges. UNESCO: Paris, 376 pp.
  20. Willox, A. et al (2013) The land enriches the soul: On climatic and environmental change, affect, and emotional health and well-being in Rigolet, Nunatsiavut, Canada. Emotion, Space and Society 6, 14-24.

Citation

Tove Björklund, Cláudia Florêncio, Rawaf al Rawaf, Tove Björklund, Rawaf al Rawaf , Juan Carlos Rocha. Arctic mobility. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 11:30:32 GMT.
Tuesday, 19 May 2015 19:51

Potential Salmon Collapse

Written by Linnéa Joandi

Potential Salmon Collapse

Main Contributors:

Daniele Crimella, Linnéa Joandi, Hanna Kylin, Kavita Oehme, Hanna Kylin

Other Contributors:

Reinette (Oonsie) Biggs, Jennifer Griffiths, Garry Peterson, Juan Carlos Rocha, Jennifer Griffiths

Summary

The potential regime shift in Alaska occurs in the marine system of the North Pacific Ocean. The present regime is characterised by a high abundance of salmon while a potential regime would be characterised by a low abundance of salmon. This is a speculative shift that has not yet occurred. The key feedbacks that maintains the current regime is the reinforcing loop of salmon population dynamics. Feedback mechanism are also present between the local communities´ needs, fishery regulation, salmon population and hatcheries´ effect. The key drivers that could cause the regime shift include climatic anomalies and extremes, fishing pressure, reduced population heterogeneity, variations in primary production, demand for food, the use of hatcheries, global warming, and changes in salmon population structure. Some possible leverage points for intervention to prevent this regime shift involves management concerned with fisheries, hatcheries and global warming.

Type of regime shift

  • Potential salmon fishery collapse

Ecosystem type

  • Marine & coastal

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • North America
  • Pacific Ocean

Region

  • Alaska, North East Pacific Ocean

Countries

  • United States

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

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  8. FAO. 2012. The state of world fisheries and aquaculture. UN Food & Agriculture Organization.
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  10. Grant WS (2012) Understanding the adaptive consequences of ecological interactions between hatchery and wild salmon in Alaska. Environ Biol Fish, Volume 94, Issue 1, pp 325-342.
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  12. Gunderson, L. H., Garmestani, A., Rizzardi, K. W., Ruhl, J., & Light, A. (2014). Escaping a Rigidity Trap: Governance and Adaptive Capacity to Climate Change int he Everglades Social Ecological System [article]. Idaho Law Review, (1), 127.
  13. Heard, W. (2012). Overview of salmon stock enhancement in southeast Alaska and compatibility with maintenance of hatchery and wild stocks. Environmental Biology Of Fishes, 94(1), 273. doi:10.1007/s10641-011-9855-6.
  14. Hilborn, R., Quinn, T. P., Schindler, D. E., & Rogers, D. E. (2003). Biocomplexity and Fisheries Sustainability. Proceedings of the National Academy of Sciences of the United States of America, (11). 6564.
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  16. Hobbie, J. E. (2014). Alaska's Changing Arctic : Ecological Consequences for Tundra, Streams, and Lakes. New York: Oxford University Press.
  17. Holtgrieve, G. W., & Schindler, D. E. (2011). Marine-derived nutrients, bioturbation, and ecosystem metabolism: reconsidering the role of salmon in streams. Ecology, 92(2), 373-385.
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  20. Kilduff, D. P., Botsford, L. W., & Teo, S. L. (2014). Spatial and temporal covariability in early ocean survival of Chinook salmon (Oncorhynchus tshawytscha) along the west coast of North America. ICES Journal of Marine Science: Journal du Conseil, fsu031.
  21. Kirby, R. R., Beaugrand, G., & Lindley, J. A. (2009). Synergistic effects of climate and fishing in a marine ecosystem. Ecosystems, 12(4), 548-561.
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  23. Krkošek, M., & Drake, J. M. (2014). On signals of phase transitions in salmon population dynamics. Proceedings of the Royal Society B: Biological Sciences, 281(1784), 20133221.
  24. Krupa, M., Stuart Chapin III, F., & Lovecraft, A. (2014). Robustness or resilience? Managing the intersection of ecology and engineering in an urban Alaskan fishery. Ecology And Society, 19(2), doi:10.5751/ES-06274-190217.
  25. Litzow, M. A., Mueter, F. J., & Hobday, A. J. (2014). Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal‐scale biological variability. Global change biology, 20(1), 38-50.
  26. Morita, K., Nagasawa, T., Tamate, T., & Kuroki, M. (2014). Temperature-dependent variation in alternative migratory tactics and its implications for fitness and population dynamics in a salmonid fish. Journal Of Animal Ecology, 83(6), 1268-1278. doi:10.1111/1365-2656.12240.
  27. Pauly, D., J. Alder, A. Bakun, S. Heileman, K. Koch, P. Mace, W. Perrin, K. Stergiou, U. Sumaila, M. Vierros, K. Freire, Y. Sadovy, V. Christensen, K. Kaschner, M. Palomares, P. Tyedmers, C. Wabnitz, R. Watson, and B. Worm. 2006. Chapter 18: Marine Fisheries Systems. Pages 1–35 in R. Hassan, R. Scholes, and N. Ash, editors. Millennium Ecosystem Assessment. Island Press, Washington, D.C.
  28. Peterman, R. M., Dorner, B., & Rosenfeld, J. S. (2012). A widespread decrease in productivity of sockeye salmon ( Oncorhynchus nerka) populations in western North America. Canadian Journal Of Fisheries & Aquatic Sciences, 69(8), 1255-1260. doi:10.1139/f2012-063.
  29. Post, E., Forchhammer, M. C., Bret-Harte, M. S., Callaghan, T. V., Christensen, T. R., Elberling, B. & Aastrup, P. (2009). Ecological dynamics across the Arctic associated with recent climate change. Science, 325(5946), 1355-1358.
  30. Quinn, T. P. (2011). The behavior and ecology of Pacific salmon and trout. UBC Press.
  31. Rand, P., Berejikian, B., Pearsons, T., & Noakes, D. (2012). Ecological interactions between wild and hatchery salmonids: An introduction to the special issue. Environmental Biology Of Fishes, 94(1), 1-6. doi:10.1007/s10641-012-9987-3.
  32. Rogers, L. A., Schindler, D. E., Lisi, P. J., Holtgrieve, G. W., Leavitt, P. R., Bunting, L., Finneyd, B. P., Selbiee, D.T., Chenf, G., Gregory-Eavesf, I., Lisach, M. J., & Walsh, P. B. (2013). Centennial-scale fluctuations and regional complexity characterize Pacific salmon population dynamics over the past five centuries. Proceedings of the National Academy of Sciences, 110(5), 1750-1755.
  33. Ruggerone, G. T., Nielsen, J. L., & Bumgarner, J. (2007). Linkages between Alaskan sockeye salmon abundance, growth at sea, and climate, 1955–2002. Deep Sea Research Part II: Topical Studies in Oceanography, 54(23), 2776-2793.
  34. Schindler, D. E., Augerot, X., Fleishman, E., Mantua, N. J., Riddell, B., Ruckelshaus, M., Seeb, J. & Webster, M. (2008). Climate change, ecosystem impacts, and management for Pacific salmon. Fisheries, 33(10), 502-506.
  35. Schindler, D. E., Hilborn, R., Chasco, B., Boatright, C. P., Quinn, T. P., Rogers, L. A., & Webster, M. S. (2010). Population diversity and the portfolio effect in an exploited species. Nature, 465(7298), 609-612. doi:10.1038/nature09060.
  36. Villamagna, A., & Giesecke, C. (2014). Adapting Human Well-being Frameworks for Ecosystem Service Assessments across Diverse Landscapes. Ecology And Society, 19(1).
  37. Walker, B., Gunderson, L., Kinzig, A., Folke, C., Carpenter, S., & Schultz, L. (2006). A handful of heuristics and some propositions for understanding resilience in social-ecological systems. Ecology and society, 11(1), 13.
  38. Wild Salmon Centre (2014). Wild Salmon Centre, Portland, Oregon, USA. Web 10 Dec 2014. http://www.stateofthesalmon.org/
  39. Yatsu, A., Aydin, K. Y., King, J. R., McFarlane, G. A., Chiba, S., Tadokoro, K., ... & Watanabe, Y. (2008). Elucidating dynamic responses of North Pacific fish populations to climatic forcing: Influence of life-history strategy. Progress in Oceanography, 77(2), 252-268.
  40. Zabel, R. W., Tyler, W., Congleton, J. L., Smith, S. G., & Williams, J. G. (2005). Survival and Selection of Migrating Salmon from Capture-Recapture Models with Individual Traits. Ecological Applications, (4). 1427.
  41. [Untitled photograph1 of Fisherman with salmon catch]. (n.d.). Retrieved November 27, 2014, from https://commons.wikimedia.org/wiki/Category:Unidentified_Oncorhynchus#mediaviewer/File:Sternfull.JPG
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  43. [Untitled photograph3 of Adult salmon]. (n.d.). Retrieved November 27, 2009, from https://commons.wikimedia.org/wiki/Category:Oncorhynchus_tshawytscha#mediaviewer/File:Chinook_salmon1.jpg

Citation

Daniele Crimella, Linnéa Joandi, Hanna Kylin, Kavita Oehme, Hanna Kylin, Reinette (Oonsie) Biggs, Jennifer Griffiths, Garry Peterson, Juan Carlos Rocha, Jennifer Griffiths. Potential Salmon Collapse. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:43:18 GMT.
Saturday, 25 January 2014 17:29

Tokaj wine region socialization

Written by Béla Kuslits

Tokaj wine region socialization

Main Contributors:

Béla Kuslits

Other Contributors:

Reinette (Oonsie) Biggs, Juan Carlos Rocha

Summary

Tokaj-Hegyalja, a wine region in north-eastern Hungary has undergone a regime shift from small-scale and high-quality wine producing strategy to a low-quality industrialized strategy. For centuries before the regime shift, mostly local families and wealthy individuals owned and operated the vineyards. The high-quality regime was maintained by the high number of wineries, the high level of local ecological knowledge and the access to the European markets where the wines were sold for good prices. After the Second World War Hungary remained under the Soviet influence, and a socialist, authoritarian regime started to govern the country. The vineyards and wineries in the Tokaj region were socialized and became parts of a large, state-operated winemaking company following a highly quantity-oriented strategy in wine-production and selling the wines in the socialist (Comcon) countries. First, the industrialized regime was forced by an external power, but later, the regime became stable as the number of wineries decreased, the local knowledge wasn't used any more and the vineyards were transformed to produce large quantities. Many high-quality but low productivity vineyards have been abandoned and became high biodiversity areas (mostly forests). Even after the political changes in 1989 the stable state remained intact as the most important factors sustaining the high-quality regime were lacking. This regime is maintained by a high demand for cheap wine, state subsidies and the missing contacts to the quality sensitive markets. Today, as the former Soviet market collapsed, the region is facing a poverty trap. As Hungary joined the European Union in 2004, the abandoned vineyards became Natura 2000 conservation areas, thus it is difficult to use them for agriculture. However, after the political changes in 1989 the state owned vineyards were privatized and there are more and more private wineries producing high-quality wines. Some of them have gained access to quality sensitive markets and started to operate in a new quality-oriented regime. It's however uncertain whether the region will flip back in the near future to a quality-oriented scheme or if it will remain a marginal strategy.

Type of regime shift

  • Governance change

Ecosystem type

  • Agro-ecosystems

Land uses

  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Conservation

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Europe

Region

  • North-eastern Hungary, Tokaj-Hegyalja World Heritage Region

Countries

  • Hungary

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. EEA. (2013). Natura 2000 data - the European network of protected sites. 03.09.2013. Retrieved from http://www.eea.europa.eu/data-and-maps/data/natura-4
  2. Hegedűs, S. (1908). Kimutatás a Tokaji borvidékhez tartozó községek szőlőterületéről és borterméséről az 1900-1907 években. In Királyok Boráról Borok Királyáról Tokaji Nektárról Folyékony Aranyról. Tokaj: Frankel Dezső Villanyerőre Berendezett Könyvnyomdája.
  3. ICOMOS. (2002). Tokaji Wine Region (Hungary).
  4. Nyizsalovszki, R., & Virók, V. (2001). Területhasználat időbeli változásai és következményei egy tokaj-hegyaljai településen. In Földrajzi Konferencia. Szeged.
  5. UNESCO. (2002). Decisions Adopted by the 26th Session of the World Heritage Committee.

Citation

Béla Kuslits, Reinette (Oonsie) Biggs, Juan Carlos Rocha. Tokaj wine region socialization. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:46:05 GMT.
Thursday, 17 October 2013 17:42

Zululand Wetlands

Written by Linda Luvuno

Zululand Wetlands

Main Contributors:

Linda Luvuno, Linda Luvuno

Other Contributors:

Reinette (Oonsie) Biggs, Donovan Kotze, Damian Walters

Summary

The shift from herbaceous (grass and sedge dominated) wetlands to swamp forest occurs when wetlands predominately covered in herbaceous vegetation become invaded by woody plant species and irreversibly change to a forest state. This shift occurs when wetlands experience disturbances that affect their hydrology and their natural disturbance regimes, notably their fire regime. In this case study in Zululand, large scale afforestation in the landscape surrounding the wetlands has changed the catchment from a system that uses a low amount of water to a system that uses large amounts of water (through different transpiration rates). This drying has led to shorter periods of soil saturation, which has altered the hydrology of the wetlands. Together with fire suppression, this has caused a shift in regime from herbaceous wetlands to wetlands dominated by indigenous swamp forest species. This regime shift has impacted biodiversity as the wetlands support a rich biodiversity of herbaceous species including the only known wild population of the critically endangered Kniphofia leucocephala. These wetlands are within one of the key water source areas of South Africa, thus this change has affected water supply. Local communities use these wetlands for grazing cattle, and this shift has reduced the area available for grazing. Removing trees from the wetlands is often difficult, therefore managerial recommendations focus on the avoidance through the establishment of a frequent fire regime (biennial) to prevent the recruitment of young trees.  

Type of regime shift

  • Herbaceous wetland to Swamp Forest

Ecosystem type

  • Grasslands

Land uses

  • Extensive livestock production (natural rangelands)
  • Timber production
  • Conservation

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Africa

Region

  • KwaZulu-Natal

Countries

  • South Africa

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Adie H, Richert S, Kiriman KP & Lawes MJ. 2011. The heat is on: frequent high intensity fire in bracken (Pteridium aquilinum) drives mortality of the sproutingrntree Protea caffra in temperate grasslands. Plant Ecology 212, 2013-2022.rn
  2. Clulow AD, Everson CS, Jarmain C & Mengistu M. 2012. Water-Use of the Dominant Natural Vegetation Types of the Eastern Shores Area, Maputaland. WRC Report No. 1926/1/12. Water Research Commission, Pretoria.
  3. Helmschrot J. 2005. Assessment of temporal and spatial effects of land use changes on wetland hydrology: A case study from South Africa. Wetlands: Monitoring, Modelling and Management. Taylor & Francis, London.
  4. Henkel JS, Ballenden C & Bayer A.W. 1936. An Account of the Plant Ecology of the Dukuduku Forest Reserve and Adjoining Areas of the Zululand Coastal belt. Annals of the Natal Museum 8(1), 95-125.
  5. Kirkman K, Goebel PC, West L, Drew MB & Palik BJ. 2000. Depressional wetland vegetation types: a question of plant Community development. Wetlands 20(2), 373-385.
  6. Kirkman LK. 1995. Impacts of fire and hydrological regimes on vegetation in Depression wetlands of Southeastern USA. In: Fire in wetlands: a management perspective. Proceedings of the Tall Timbers Fire Ecology Conference, No. 19. Tall Timbers Research Station, Tallahassee, Florida.
  7. Le Maitre DC, Scott DF & Colvin, C. 1999. A review of information on interactions between vegetation and groundwater. Water SA 25(2), 137-151.

Citation

Linda Luvuno, Linda Luvuno, Reinette (Oonsie) Biggs, Donovan Kotze, Damian Walters. Zululand Wetlands. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2013-10-24 14:41:30 GMT.
Thursday, 16 May 2013 10:17

Northern Benguela Marine System

Written by Catarina Larsson

Northern Benguela Marine System

Main Contributors:

Sophie Belton, Carolina Holmberg, Catarina Larsson, Shauna Mahajan

Other Contributors:

Juan-Paul Roux, Juan Carlos Rocha

Summary

This case study examines one of the regime shifts that took place in the Northern Benguela system; occurring in the 1990s from a high to low fish biomass state. This shift has been attributed to consistent overfishing, and was enhanced by large-scale environmental anomalies that occurred in the 1990s. Multiple drivers and feedbacks keep the system locked in the low biomass state. Jellyfish have exponentially grown in numbers, occupying the niche left by pelagic fish and suppressing regrowth in many stocks. Warmer sea temperatures decrease the ability for fish to spawn, keeping fish biomass low. Low fish biomass coupled with hypoxic events leads to phytoplankton blooms and reinforces the frequency and spatial scale of severe hypoxic conditions. The new, low biomass state has negatively impacted provisioning services from marine resources, regulating services maintaining marine water quality, and recreational fishing services. The loss in ecosystem services has both directly and indirectly impacted the well-being of multiple resource users within the system. Management of the system is now moving from a single-species approach towards an ecosystem-based management approach that takes into account trophic interactions as well as environmental variations affecting the system. This means, for example, setting catch limits for fisheries based on more than just fish biomass.

Type of regime shift

  • Marine food webs

Ecosystem type

  • Marine & coastal

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Africa
  • Atlantic Ocean

Region

  • Coast off south West African continent

Countries

  • Namibia

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Species introduction or removal
  • Environmental shocks (eg floods)

Land use

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots)
  • Extensive livestock production (rangelands)
  • Conservation
  • Tourism

Impacts

Ecosystem type

  • Freshwater lakes & rivers

Key Ecosystem Processes

  • Nutrient cycling
  • Water cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Livestock
  • Fisheries
  • Hydropower

Regulating services

  • Water purification
  • Pest & Disease regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Years

Reversibility

  • Unknown

Evidence

  • Models
  • Contemporary observations
  • Experiments

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Alternate regimes

Invasive floating plant dominance

This regime is characterized by dense, mono-specific mats of free-floating invasive plants that cover vast areas of the water’s surface. The water below lacks adequate light for many species to survive and biodiversity is restricted. These mats can completely conceal the water-body beneath and as they are free floating they can be displaced by flash floods and strong winds, often damaging hydroelectric equipment and causing a sudden change in ecosystem structure and function.

 

Invasive submerged plant dominance

Dense monocultures of rooted submerged invasive plants dominate the system, often not seen until they reach the water’s surface by which point they are usually problematic. Native vegetation is out competed, and whilst initially these plants can push up levels of dissolved oxygen and improve water quality they rapidly grow to a state where only the plants near the waters’ surface are healthy and just below the water is turbid and hypoxic. Water flow is also limited and pumping mechanisms can become clogged and damaged, increasing flood risk. These plants often reproduce via fragmentation and can easily be spread through river systems by wildlife, people, boats and often by the machines used to mechanically clear the plants from invaded areas.

Drivers and causes of the regime shift

Shift from floating invasive to submerged invasive plant dominance

The main causes of the regime shift, we believe, are the biological control of floating invasive plants in freshwater systems. Nutrients that were previously locked within the floating invasive plants are now available for submerged invasive plants to acquire. Another major factor is the intrinsic nature of these systems, they are man-made and historically not a common feature of South African topography meaning there are fewer native species to readily occupy them. As the floating plants are controlled there may not be a good stock of native submerged plants to utilize the resources and instead resilience is very low in this unstable state. Poorly regulated human activities such as waste water treatment and unregulated agricultural endeavors have also led to problematically high nutrient loading in many of these systems.

How the regime shift worked

Shift from floating invasive to submerged invasive plant dominance

The invasive floating plant regime often occurs in man-made, impounded freshwater systems in South Africa. The invasive plants have often been intentionally introduced via the aquarium and ornamental trade, and un-intentionally via ‘hitchhiking’ on other species and aquatic machinery. In many cases external nutrient loading facilitates their growth and minimizes the impact of biological control agents therefore perpetuating the regime. The floating plants quickly form mats that block light to the water column, which can reduce the presence of other aquatic plants that might compete for resources, again maintaining their dominance. Eventually they can alter the whole ecosystem structure and function diminishing the presence of and access to quality freshwater.

Once invasive floating plants are dominant biological control agents may be introduced to control the floating plants, with the hope of inducing a regime shift to a clear water system with healthy biodiversity and good quality water. However, the regime shift we believe is happening in many systems is quite different. As the floating plants decompose dues to the effects of control agents the system receives a sudden influx of freely available nutrients, and at the same time light levels within the water column are restored. As nutrients, light and space become available submerged invasive plants are able to utilize the resources and establish.

The submerged plants’ ability to photosynthesize temporarily increases the levels of dissolved oxygen in the water column thus improving water quality (short-term) and allowing the submerged plants to become dominant. After this period of improvement, the water quality deteriorates as the plant biomass crosses a threshold after which it begins to block out light, reduce biodiversity and alter sediment stability. External nutrient loading further facilitates their growth and helps to sustain the new invasive submerged plant regime.

Impacts on ecosystem services and human well-being

Shift from floating invasive to submerged invasive plant dominance

This regime shift leads to diminished access to quality freshwater. Livelihoods that are dependent on South Africa’s freshwater biodiversity, such as fishing and eco-tourism are also compromised (Charles and Dukes, 2007). As are all activities that depend on access to freshwater for irrigation and livestock. Many farmers have lost livestock to drowning as they perceive large mats of floating plants to be solid underfoot (McConnachie et al, 2003). Hydroelectric pumps are damaged, once again limiting water access, and the costs related to repairing these and to the mechanical/chemical control of the submerged plants can be substantial.

Besides impacts of economic activities and livelihoods, this regime shift also directly impacts human well-being. Invasive aquatic plants play a key role harboring vectors of diseases such as schistosomiasis (bilharzia) and malaria (Mack and Smith, 2011). Continued mismanagement of invasive plants in South Africa, perpetuated by poor understanding of the systems, leads to incorrect spending of state funding potentially affecting a wider cross-section of people and communities than those directly affected. Protection against natural disasters are also affected, as floods defenses are compromised by the plants which alter water flow and can increase water levels by raising sedimentation.

Management options

Potentially, once the dominating invasive submerged plants are controlled (manually, physically or biologically) there could be a shift back to the floating plant dominance if the environmental conditions that facilitated the floating plants have not changed or been managed and if no ‘reserve’ of the floating plant has been left to support a population of it’s bio-control agents.

By reducing levels of eutrophication alongside the control of invasive floating plants we can increase resilience against colonization from submerged plants. We also propose that increasing local levels of native vegetation (via seed banks and plant stocking) in systems before the control of the floating plants is underway could increase resilience as there would be less resources available for invasive plants to utilize.

Key References

  1. Bakun, A., Field, D.B., Redondo-Rodriguez, A. and Weeks, S.J. 2010. Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems.rnGlobal change biology. 16: 1213-1228. rn
  2. Berkes, F., Hughes, T.P., Steneck, R.S., Wilson, J.A., Bellwood, D.R., Crona, B., Folke, C., Gunderson, L.H., Leslie, H.M., Norberg, J., Nystru00f6m, M., Olsson, P., u00d6sterblom, H., Scheffer, M., Worm, B. 2006. Globalization, Roving Bandits, and Marine Resources. Science. 311 (5767): 1557-1558.
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  10. Cury, P. and Shannon, L. 2004. Regime shifts in upwelling ecosystems: observed changes and possible mechanisms in the northern and southern Benguela. Progress in Oceanography. 60:223-243.
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  12. Food and Agricultural Organization (FAO).1996. Precautionary approach to capture fisheries and species introductions. Technical guidelines for responsible fisheries. No. 2.
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  17. Hutchings, L., van der Lingen, C.D., Shannon, L.J., Crawford, R.J.M., Verheye, H.M.S.,rnBartholomae, C.H., van der Plas, A.K., Louw D., Kreiner A., Ostrowski M., Fidel Q., Barlow R.G., Lamont T., Coetzee, J., Shillington, F., Veitch, J., Currie, J.C., and Monteiro, P.M.S., 2009. The Benguela Current: An ecosystem of four components. Progress in Oceanography. 83:15-32. rn
  18. Kreiner, A., Yemane, D., Stenevik, E.K. and Moroff, N.E. 2011. The selection of spawning location of sardine (Sardinops sagax) in the northern Benguela after changes in stock structure and environmental conditions. Fisheries oceanography. 20(6): 560-569. rn
  19. Lynam, C.P., Gibbons, M.J., Axelsen, B.E., Sparks, C.A.J., Coetzee, J., Heywood, B.G and Brierley, A.S. 2006. Jellyfish overtake fish in a heavily fished ecosystem. Current Biology. 16(13).
  20. Monteiro, P.M.S and van der Plas, A.K. 2006. Low oxygen water (LOW) variability in the Benguela system: Key processes and forcasting relevant to forecasting. Benguela Predicting a Large Marine Ecosystem, Large Marine Ecosystems. 14:71-90.
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Citation

Sophie Belton, Carolina Holmberg, Catarina Larsson, Shauna Mahajan, Juan-Paul Roux, Juan Carlos Rocha. Northern Benguela Marine System. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2013-08-26 08:47:14 GMT.
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