Common pool resource harvesting
A community derives ecosystem services by extracting from a renewable resource such as water, fish, or forest. If a harvester is overharvesting (a defector), he/she is ostracised by the community, for example by obstructing their access to necessary machinery or to market, which encourages the defector to co-operate by harvesting at a lower, socially optimal level. The alternative regimes are (1) high co-operation and resource levels and (2) overharvesting. Key drivers include resource inflow, the effectiveness of the ostracism norm, and the cost of harvesting. Key impacts include degradation in the state of the resource and harvester payoff and wellbeing. Evidence is currently confined to modelling studies.
Key direct drivers
- Harvest and resource consumption
- Environmental shocks (eg floods)
- Small-scale subsistence crop cultivation
- Large-scale commercial crop cultivation
- Intensive livestock production (eg feedlots)
- Extensive livestock production (rangelands)
- Timber production
- Marine & coastal
- Freshwater lakes & rivers
- Temperate & boreal forests
- Tropical forests
- Moist savannas & woodlands
- Drylands & deserts
- Mediterranean shrubs (eg Fynbos)
- Food crops
- Wild animal and plant products
- Fuel and fiber crops
- Livelihoods and economic activity
Typical spatial scale
Typical time scale
Confidence: Existence of RS
- Speculative – Regime shift has been proposed, but little evidence as yet
Confidence: Mechanism underlying RS
- Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms
Co-operation and sustainable resource levels
Harvesters extract from the resource at rates that are socially optimal, ensuring that resource levels stay at their most productive level and the community-average payoff is high. Social capital exists within the community, ensuring any defectors are ostracised.
Harvesters exert high efforts in extracting the resource, leading to depletion of the resource and low payoffs for the community. Social capital is absent and defectors are not ostracised.
Drivers and causes of the regime shift
Shift from ‘Co-operation and sustainable resource levels’ to ‘Over-harvesting’
The regime shift occurs when ostracism ceases to be an effective mechanism for encouraging defectors to co-operate, because the benefits of overharvesting begin to outweigh the disadvantages of ostracism. A number of factors could drive this shift. Increasing resource level, for example due to increased inflow, can lead to ineffective ostracism because at higher resource levels defection becomes more attractive by providing higher gains from resource over-extraction. Increasing defector payoff compared to ostracism, for example due to decreased costs or decreased ostracism strength, could also lead to defection becoming increasingly attractive.
Shift from ‘Over-harvesting’ to ‘Co-operation and sustainable resource levels’
Reversal of any of the above trends can cause a shift from over-harvesting to co-operation: decrease in resource levels, for example due to decreased inflow; increased costs; or increased ostracism strength.
How the regime shift works
Co-operation and sustainable resource levels occur when there is sufficient social capital to ostracise defectors and thereby make defection less attractive than co-operation. The key negative feedback that keeps the regime stable is the following: if the fraction of cooperators increases the social capital and hence strength of ostracism increases which reduces the utility of defectors, making defection less attractive. At the same time, however, resource productivity increases which increases the utility of defectors, so stability ultimately depends on the respective strength of the two feedback loops.
The over-harvesting regime exists when there are only few cooperators and hence there is insufficient social capital to ostracise defectors. The feedback that maintains full defection is as follows: any agent that 'co-operates' (i.e. harvests at a lower level) will have a payoff substantially less than the defectors. In the absence of social capital to encourage co-operation through ostracism, the co-operator will switch back to defection. The key threshold for a collapse in co-operation is when the costs of ostracism are lower than the benefits of overharvesting, i.e. ostracism ceases to be an effective mechanism to discourage defection. A variety of drivers can cause this shift, as discussed below.
To trigger a transition from full defection back to co-operation, co-operation must become more attractive than defection. This could be achieved by increasing the costs of harvesting, or by decreasing the level of the resource to low levels so that the benefits of overharvesting are minimal. However, once the co-operation strategy is lost in the community, it may be very difficult for it to re-emerge.
Impacts on ecosystem services and human well-being
The ability of the natural system to provide resources for harvesting is lost with the regime shift from co-operation to over-harvesting (gained for over-harvesting to co-operation). Depending on context, loss of other ecosystem services many accompany the decline in resources. The income that members of the harvesting community obtain by harvesting is severely decreased by this regime shift. Income may even no longer exceed the costs of harvesting and the community may need to find other means of survival.
Options for preventing regime shift to over-harvesting
Management actions that stop the drivers discussed above reaching their thresholds may help to prevent regime shifts. Activities that strengthen social norms and trust in the community and thus enhance cooperation and decrease the incentive to defect and overharvest for the individual benefit (hence increasing the strength of the ostracism).
Options for restoration of co-operation:
Introducing measures that build trust in the community and disincentivise free riding.
Lade SJ, Tavoni A, Levin SA & Schlüter M. 2013. Regime shifts in a social-ecological system. Journal of Theoretical Ecology 6:359-372.
Tavoni A, Schlüter M, Levin S (2012), The survival of the conformist: Social pressure and renewable resource management, Journal of Theoretical Biology 299:152-161