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Incorporating climate change in a harvest risk assessment for polar bears Ursus maritimus in Southern Hudson Bay

May 19, 2021

Arctic marine mammals are harvested by Indigenous people for subsistence and are socially and culturally important. For ice-dependent species like the polar bear Ursus maritimus, management and conservation require understanding interactions between harvest and sea-ice loss due to climate change. We developed a demographic model to evaluate harvest risk for polar bears in Southern Hudson Bay, Canada, where the annual ice-free season has increased by approximately one month in recent decades. The model was based on the theta-logistic equation and allowed for density-dependent changes (through carrying capacity [K]) and density-independent changes (through population growth rate [r]). Model parameters were estimated using a Bayesian Monte Carlo method that included capture-recapture, aerial survey, and harvest data. Harvest management followed a state-dependent approach under which new estimates of abundance were used to update the harvest level every five years. Under a middle-of-the-road environmental scenario that assumed K and r would decline in proportion to projected sea-ice declines, annual removal of 0.02–0.03 of females resulted in a 0.8 probability of maintaining subpopulation abundance above maximum net productivity level for three polar bear generations (~34 years), our primary criterion for sustainability. Under more pessimistic and optimistic environmental scenarios, comparable female harvest rates were 0.01 and 0.055, respectively. Our coupled modeling-management framework can be used to inform tradeoffs between protection and sustainable use for wildlife populations experiencing habitat loss.

Publication Year 2021
Title Incorporating climate change in a harvest risk assessment for polar bears Ursus maritimus in Southern Hudson Bay
DOI 10.1016/j.biocon.2021.109128
Authors Eric V. Regehr, Markus Dyck, Samuel A. Iverson, David S. Lee, Nicholas J Lunn, Joseph M Northrup, Marie-Claude Richer, Guillaume Szor, Michael C. Runge
Publication Type Article
Publication Subtype Journal Article
Series Title Biological Conservation
Index ID 70220861
Record Source USGS Publications Warehouse
USGS Organization Eastern Ecological Science Center