Decision analysis rooted in Indigenous and Western scientific knowledge identifies cost‐effective strategies for managing hyperabundant deer to restore keystone places

Abstract The hyperabundance of herbivores—a result of altered human relationality with the land and the extirpation of predators—is leading to large‐scale degradation of keystone ecosystems across the globe. Designing and implementing socially acceptable and cost‐effective strategies that meaningfully reduce herbivore populations while allowing for the recovery of ecological function and cultural relationality is an inherently complex issue. As a result, decision paralysis is common, leading to delayed or avoided action and continued ecosystem loss and degradation. Using a structured decision‐making process that incorporated expert elicitation, population modelling and cost‐effectiveness analyses while honouring multiple knowledge systems, we identified five discrete and four portfolio strategies for managing hyperabundant black‐tailed deer ( Odocoileus hemionus columbianus ) in the Southern Gulf Islands of British Columbia, Canada, with consideration to benefit, feasibility and cost objectives. Hunting led by local Indigenous Nations was ranked the most cost‐effective strategy when benefits considered well‐being of peoples and place holistically, and accounted for both Indigenous and Western science worldviews. When only Western perspectives were included, increased licensed hunting by local communities and hiring professional deer reduction specialists were ranked the most cost‐effective. However, while increased licensed hunting had a >50% likelihood of project uptake and success (i.e. feasibility), the strategy had <50% likelihood of achieving any benefit objective. In comparison, Indigenous‐led hunting, professional deer reduction specialists, and all portfolio strategies had >50% likelihood of meeting at least one benefit objective, although only Indigenous‐led hunting also had >50% likelihood of achieving feasibility objectives. Synthesis and applications . We provide a roadmap for decision‐makers across the globe to robustly and transparently assess the problem of herbivore hyperabundance and inform solutions within their context. Within the Salish Sea, our work highlights the need to support hunting, and in particular, Indigenous‐led hunting, as cost‐effective strategies to promote revitalization of well‐being of peoples and place. Read the free Plain Language Summary for this article on the Journal blog.