Projecting the future of a threatened marine mammal in relation to climate warming

Climate warming is expected to impact global biodiversity, especially in the rapidly warming Arctic. There is an urgent need to evaluate the demographic effects of climate warming under different greenhouse gas emission pathways to guide wildlife management and inform listing decisions under protected species legislation. We used forecasted environmental variables to drive a novel demographic model for the ringed seal (Pusa hispida), a circumpolar Arctic marine mammal and critical subsistence resource for Indigenous people. Under the most demographically plausible conditions and assumptions, the projected abundance of ringed seals in the Chukchi Sea west of Alaska, USA, changed by an average of -7% (range -25% to 4%) by 2058 and -71% (range -96% to -8%) by 2100. The choice of greenhouse gas emissions pathway was the most important determinant of population outcomes through its influence on two habitat variables, snow-on-ice depth and sea-ice area. The choice of climate model, the intrinsic population growth rate, density dependence, and polar bear predation had a moderate influence on population projections, while harvest by Alaska Natives had a small influence. Modeling results suggest that ringed seals in the Chukchi Sea can exhibit stable or increasing recruitment at average April snow-on-ice depths below 20-30 cm. Given that declining snow depth was central to listing the species as threatened under the U.S. Endangered Species Act, our work both represents the first quantitative investigation of future abundance for Alaskan ringed seals and is relevant to conservation assessments for the species.