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

Sustainable wildlife harvest is challenging due to the complexity of uncertain social-ecological systems, and diverse stakeholder perspectives of sustainability. In these systems, semi-complex stochastic simulation models can provide heuristics that bridge the gap between highly simplified theoretical models and highly context-specific case-studies. Such heuristics allow for more nuanced recommendations in low-knowledge contexts, and an improved understanding of model sensitivity and transferability to novel contexts. We develop semi-complex Management Strategy Evaluation (MSE) models capturing dynamics and variability in ecological processes, monitoring, decision-making, and harvest implementation, under a diverse range of contexts. Results reveal the fundamental challenges of achieving sustainability in wildlife harvest. Environmental contexts were important in determining optimal harvest parameters, but overall, evaluation contexts more strongly influenced perceived outcomes, optimal harvest parameters and optimal harvest strategies. Importantly, simple composite metrics popular in the theoretical literature (e.g. focusing on maximizing yield and population persistence only) often diverged from more holistic composite metrics that include a wider range of population and harvest objectives, and better reflect the trade-offs in real world applied contexts. While adaptive harvest strategies were most frequently preferred, particularly for more complex environmental contexts (e.g. high uncertainty or variability), our simulations map out cases where these heuristics may not hold. Despite not always being the optimal solution, overall adaptive harvest strategies resulted in the least value forgone, and are likely to give the best outcomes under future climatic variability and uncertainty. This demonstrates the potential value of heuristics for guiding applied management.

Sustainability of wildlife harvest in stochastic social-ecological systems

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.

Trends in high arctic muskox (Ovibos moschatus) harvest, 1990-2015

Harvest reporting has been in place for High Arctic muskoxen in Nunavut, Canada, since 1990-91. The communities of Resolute, Grise Fiord, and Arctic Bay harvest muskoxen in the region. Overall, muskox harvest has declined in Resolute and Grise Fiord since the 1990s. The recovery of Peary caribou populations on the Bathurst Island Complex, which provides an alternate preferred source of country food, may be a factor behind Resolute’s decreased muskox harvest. The proportion of harvest for domestic use has also declined relative to sport hunts, which have remained relatively constant since the 1990s. We compared muskox harvest from tag records and reported harvest, i.e., the voluntary surveys to the Nunavut Wildlife Harvest Study for muskoxen. It is clear that voluntarily reported harvest underestimates actual harvest, but not consistently enough to predict the actual harvest. Muskox populations are at historic high levels on Bathurst Island, southern Ellesmere Island, and Devon Island and could support more harvest than is currently taken. Changes to Total Allowable Harvests and management unit boundaries in 2015, combined with a decline in the availability of Baffin Island caribou as country food, may result in increased harvest pressure on muskoxen in the High Arctic.