Vegetation regime shifts in Yamal-Nenets

Feedback mechanisms

Open land with reindeer herding

  • Open land maintaining feedback (local, certain): Open land with reindeer herding regime is maintained by a strong reinforcing feedback loop. As reindeer and Nenets roam across the land, they trample and graze on the vegetation cover (lichens, moss, graminoids, and small deciduous shrubs) (Yu et al. 2011; van der Wal 2005). Simultaneously, the reindeer excrete nutrient rich feces and urine, which promotes growth of lichens, mosses, and graminoids, thus helping to maintain the open landscape (van der Wal et al. 2005).
  • Nenets-reindeer feedback (regional, certain): The number of nomadic herding Nenets is loosely linked to the number reindeer on the Yamal Peninsula - the more Nenets there are, the more reindeer they can take care of. For instance, the number of reindeer reportedly have been rising since the end of World War II, now reaching a total of 630 000. The number of Nenets have also grown in recent years: form 3552 in 1981 to 5000 in 2009 (Forbes et al. 2013). Judging by the growth and popularity of the nomadic Nenets, it could be argued that if the land could hold more reindeer, there could be an increase in the number of Nenets. However, it is important to note that this feedback is largely driven by what happens with gas exploitation development.


Shrubland without reindeer herding

  • Shrub maintaining feedback (local, certain): Shrubs trap snow underneath it’s canopy which both creates a microclimate that keeps the snow trapped beneath the shrub and creates an insulating layer that warms the soil temperature. A warmer soil temperature allows for more microbial activity and an increased nutrient availability. Organic matter that gets trapped underneath shrubs decomposes and contributes the increased nutrient availability. In turn, this process leads to the establishment of more shrubs (Myers-Smith 2007).
  • Temperature increase feedback (global, certain): Many studies have demonstrated a link between climate change, Arctic warming, and shrub encroachment (for review, Walker et al. 2006). Increased Arctic temperatures create a more suitable environment for shrubs to establish (Myers-Smith 2007). Additionally, there is some evidence to support the notion that the length of growing season has also extended over the last decade (Zeng et al. 2013), allowing shrubs to advance further up the tundra. The more shrubs that grow on the tundra, the more heat is absorbed by the shrubs, and thus reduce the Yamal Peninsula’s Albedo (Strum et al. 2005), or in other words, ability to reflect heat. It is important to note that the link from Albedo to climate change is represented by a dotted line on our causal loop diagram. This is because it is unclear how much of an impact the Yamal Peninsula has on global climate change.


Shift from open land with reindeer herding to shrubland without reindeer herding

According to Grace et al. (2002), low temperatures in the tundra limit the photosynthesis rates and the utilization of its products, nutrient mineralization, and litter decomposition. All these factors limit tree and shrub growth in the tundra. In addition, an increase in one of these factors could not lead to shrub growth in the tundra; it is necessary that these factors increase together to make possible the shrub growth in this ecosystem.

Due to the short growing season, a small increase in temperature will produce large effects on shrub growth in the tundra (Grace et al., 2002). During the last fifty years the temperature has increased 1-2 oC in the tundra (Aune et al., 2011).

The main external direct driver that causes the shift from moss, lichen, graminoid dominated tundra to shrub encroachment is global warming (Kullman, 2002; Sturm et al., 2005; Myers-Smith, 2007; Aune et al., 2011; Yu et al., 2011; Macias-Fauria et al., 2012). The increase in temperature not only leads to warmer winters and summers but also lengthens the growing season in the tundra.

This global-scale driver increases growth rates in shrubs, microbial activity, and nutrient fluxes (Myers-Smith, 2007; Yu et al., 2011). The enhancement of shrub growth produces a shade that inhibits the presence of moss, lichen, and grass in the tundra ecosystem, leading to shrub densification (see Table 1).


Shift from Shrubland without reindeer herding to open land with reindeer herding

Reindeer grazing is the most important driver controlling shrub densification in the tundra (Myers-Smith, 2007; Yu et al., 2011). During summer, the reindeer populations graze deciduous shrubs, graminoids, forbs, and lichens, but evergreen shrubs. This is because evergreen shrubs have low nitrogen concentration and poor digestibility (Yu et al., 2011); however, evergreen shrubs decline through time because they have slow growth rates and they are affected by reindeer trampling, which leads to a transition from shrub-dominated tundra to moss and graminoid-dominated tundra.


Another driver that could control shrub expansion is the infrastructure related to gas exploitation. This infrastructure has caused changes from shrubs and mires to barren land (Kumpula et al., 2012).


Slow internal system changes


The rise of temperature at global level has triggered slow variables in Yamal Peninsula such as accelerating shrub growth and nutrient cycling (Myers-Smith, 2007), changing species composition (Myers-Smith, 2007).


Other important slow internal system changes are the population of nomadic Nenets – from 3,552 persons to 5000 currently-, and reindeer population – from 310,000 reindeers after World War II to 610,000 reindeers today; 300,000 of them are in the Yamal Peninsula- (Forbes et al., 2009). The duplication of reindeer population during the last six decades explains the overgrazing in the Yamal Peninsula.


Kumpula et al. (2012) established that gas exploitation infrastructure has changed traditional reindeer migration routes. However, it is not clear how this change has modified the vegetation in the Yamal Peninsula. Table 3 summarizes the slow variables in the Yamal Peninsula.

Summary of Drivers

# Driver (Name) Type (Direct, Indirect, Internal, Shock) Scale (local, regional, global) Uncertainty (speculative, proposed, well-established)
1 Temperature Direct, external Global Well-established
2 Shrub shade Direct, internal Local Speculative
3 Grazing Direct, external regional Well-established
4 Gas exploitation Direct, external Regional Well-established

Key thresholds

Shift from open land with reindeer herding to shrubland without reindeer herding,

  • Threshold 1: Increased temperatures that open up for shrub encroachment, through longer growing seasons, warmer soils and higher litter decomposition rates.
  • Threshold 2: Overgrazing from reindeers. It has been observed that evergreen shrubs expand on areas largely grazed by reindeers (Yu et al., 2011).
  • Threshold 3: Undergrazing from reindeers. Without heavy grazing pressure, shrubs will eventually dominate (see Threshold 1).

Shift from shrubland without reindeer herding to open land with reindeer herding

  • Threshold 1: Reindeer density. Up to a certain amount of reindeers grazing, areas dominated by shrubs such as willows, will stay in the shrub state. At a threshold level the amount of reindeers will be so high that the trampling and grazing reduces enough shrubs to shift the vegetation to a graminoid-dominated state


Leverage points

The amount of reindeers in the area is seen as the main a leverage points since they are representing the rate of grazing, together with trampling and nutrient inputs from feces/urine that are the main drivers for keeping a stable state of graminoid instead of shrubs in the area (Forbes et al 2009). The indirect driver behind these rates are legislation as in laws and rules, which in present time is not enough to address the full range of problems that arise during the practice and coexistence of the gas companies, the non-indigenous workers and the Nenets nomads (Kumpala et al, 2012). A change in legislation could affect the way the parts of this SES interact, changing the system’s dynamics and its emergent property. The rate of grazing is mainly a leverage point that is affecting the Nenets themselves and the vegetation, it does not affect the gas companies and their workers as much. The grazing rate could be assumed to be a leverage point with high certainty according to the literature assessed in this regime shift assessment.


Temperature as a result of climate change is clearly affecting this SES, which means that the total anthropogenic greenhouse gas activity is a global leverage point. At the regional scale within the Yamal-Nenets' SES, temperature is suggested as a leverage point. This is associated with a high level of uncertainty since it is very hard to estimate the possibility to mitigate and adjust the system. It is a leverage point that is considered to affect all parts/actors within the SES. Consequences of increased temperatures in northern ecosystems will be thawing permafrost, increased forest fire frequency and shifting ecosystem boundaries (Myers-Smith 2007).

The gas market, tightly interconnected with gas exploitation, is also considered to be a main leverage point for the Yamal-Nenets’ SES on a both regional and global scale. The gas market is the main driver, enforced by humans, which means opportunity to transform in a desirable way. The system could either be transformed through a shift in global energy production, or through market intervention when internalizing the externalities. Different kinds of policy instruments could be used. Also, feed-in tariffs could be used to boost production of renewable energy so that the direction that this SES is having, change in a more long-term and sustainable direction (Couture & Gagnon, 2010). The gas market is a leverage point for both the Nenets and the gas workers/companies in the area since it affect the rate in which the gas exploitation is being conducted.

Summary of Ecosystem Service impacts on different User Groups

References (if available)
Provisioning Services
Food Crops
Feed, Fuel and Fibre Crops
Livestock - (Forbes et al., 2009)
Wild Food & Products + (Forbes et al., 2009, Kumpala et al., 2012)
Timber - (Dagteva & Nelleman, 2013)
Regulating Services
Air Quality Regulation
Climate Regulation + (Walker et al., 2011, Myers-Smith, 2007, Zimov et al., 1995)
Water Purification
Soil Erosion Regulation
Pest & Disease Regulation
Protection against Natural Hazards
Cultural Services
Recreation + (Dagteva & Nelleman, 2013, Kumpala et al., 2012)
Aesthetic Values + (Dagteva & Nelleman, 2013, Kumpala et al., 2012, Forbes et al., 2009)
Cognitive & Educational + (Dagteva & Nelleman, 2013, Kumpala et al., 2012)
Spiritual & Inspirational + (Dagteva & Nelleman, 2013, Kumpala et al., 2012)

Uncertainties and unresolved issues

It is not clear how severe the impacts of climate change, i.e. increased temperatures, will be in Yamal and the Arctic in general. As for now, a high density of reindeers in Yamal keeps the otherwise expected and observed shrub encroachment away. Depending on other feedbacks in the Arctic, like thawing permafrost, ocean temperatures and the melting summer sea ice - and the result of global attempts to mitigate carbon emissions - the shrub encroachment could take different trajectories.

Another unresolved issue concerns the carrying capacity for reindeers. As gas exploitation continues to increase, the density and abundance of reindeer would need to adjust in order to remain at the appropriate carrying capacity for the newly defined landscape. For this reason, the reindeer population needs to be continually monitored to ensure that reindeer do not under- or overgraze the land, causing a shift to the shrub dominated regime.

A last uncertainty regards the future of the Yamal-Nenets SES in itself, on which the anticipated large increase in gas exploitation could have detrimental effects, scientists warn. Forbes et al., 2009 write: “We envision a looming threshold related to the sheer scale of future expected needs of industry for territory, concomitant pasture, and lake/river degradation, coupled with a rapidly growing industrial workforce at the same time as climate is warming.”


Forbes et al. describe a possible alternative state for the Nenets social-cultural system, which “would imply a significant reduction of reindeer nomadism in the area, if more attention is not paid to building a constructive dialogue for the future.” A state like this “would reverse Nenets nomads’ generally supportive approach to mutual coexistence with industry. The likely outcome for newly sedentary herders would be resignation, alcohol abuse, suicide, and domestic violence” (Forbes et al., 2009).