Heuristics for the sustainable harvest of wildlife in stochastic social-ecological systems

Abstract

1.Sustainable wildlife harvest is challenged by complex and uncertain social-ecological systems, and diverse stakeholder perspectives. Heuristics could provide one avenue to integrate scientific principles and understand potential conflict in data-poor harvest systems. Management Strategy Evaluation (MSE) can be a useful tool to explore harvest options and implications from diverse perspectives, and aid in heuristic development.2.We ran 176,910 stochastic simulation models to develop heuristics for sustainability in wildlife harvest systems. Environmental contexts included three simulated species distributed across the slow-fast life-history gradient (the great-unicorn, lesser-unicorn, and phoenix), two variability/uncertainty levels, and three starting population sizes. Optimal outcomes from four harvest strategies (constant, proportional, threshold-proportional, and threshold-increasing-proportional) were assessed under evaluation contexts reflecting multiple environmental, harvester, manager and societal sustainability objectives and ethical perspectives.3.The results reveal fundamental challenges in obtaining sustainable outcomes in harvest systems: few scenarios produced good scores across all evaluation metrics and ethical perspectives. Composite evaluation metric sets and ethical perspectives strongly influenced perceived outcomes. Rawlsian ethical perspectives (considering the minimum score of multiple objectives) often revealed severe trade-offs between individual metrics, even when Utilitarian ethical perspectives (averaging scores of multiple objectives) view the same scenarios positively. Simple composite metrics popular in the theoretical literature often diverged from the holistic metrics that better reflect applied contexts.4.Threshold and proportional systems performed better than constant harvest under Utilitarian ethics in 79-90% of cases, and 34-39% of cases with Rawlsian ethics. However, no strategy was optimal overall: each harvest system tested was near-optimal in at least one evaluation context in every environmental context.5.Synthesis and applications. Given a lack of a singular optimum strategy, we recommend harvest systems should be chosen with clear reference to contextually appropriate metrics and ethics of interest when optimizing harvest systems for sustainability. Importantly, management recommendations focused on maximizing harvest should be treated with skepticism if this is not explicitly identified as a key value for that socio-ecological system.