Institutional strategy update speed affects extinction probabilities among harvested species

Edward Tekwa, Zoology, University of British Columbia, Vancouver, BC, Canada, Malin L. Pinsky, Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ and Juan A. Bonachela, Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ

Background/Question/Methods
Human harvesting can lead to extinctions. A species’ potential yield, economic value, and harvesting cost can determine whether overharvesting or conservation ensues, but it is unclear how these human behaviours translate to extinction probabilities and how institutional arrangements affect this translation. Here, we model institutions that adapt harvesting strategies to short-term profit, and explore how variations in strategy update speed interact with ecological and economic factors to affect extinction probabilities.
Results/Conclusions
We found that fast institutions result in the open-access tragedy of the commons, where highly valued and low-yield species are prone to extinction. In contrast, slow institutions result in exclusive access and path dependence, such that low-valued and high-yield species likely go extinct if they are historically overharvested. Surprisingly, institutions with intermediate speed maintain the lowest extinction probabilities overall across ecological and economic conditions because institutions cannot determine the correct adaptive increment in harvest rate to increase utility. Each institution type exhibits a different risk and reward profile in terms of extinction probability and stock levels of species that persist. Our results show that: 1.institution update speed is a consequential parameter for species extinction with little theoretical precedence; and 2. institutions attaining conservation targets may have nothing in common depending on ecological and economic conditions, unlike the current paradigm that such ecologically successful institutions should share at least a few common traits like property rights. These theoretical insights point to a complex extinction landscape where causal inferences and policy recommendations must account for non-linear dynamics arising from a gradient of time-scale differences.