Demographic risk assessment for a harvested species threatened by climate change: Polar bears in the Chukchi Sea

Ecological Applications
By: , and 

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Abstract

Climate change threatens global biodiversity. Many species vulnerable to climate change are important to humans for nutritional, cultural, and economic reasons. Polar bears Ursus maritimus are threatened by sea-ice loss and represent a subsistence resource for Indigenous people. We applied a novel population modeling-management framework that is based on species life history and accounts for habitat loss to evaluate subsistence harvest for the Chukchi Sea (CS) polar bear subpopulation. Harvest strategies followed a state-dependent approach under which new data were used to update the harvest on a predetermined management interval. We found that a harvest strategy with a starting total harvest rate of 2.7% (˜85 bears/yr at current abundance), a 2:1 male-to-female ratio, and a 10-yr management interval would likely maintain subpopulation abundance above maximum net productivity level for the next 35 yr (approximately three polar bear generations), our primary criterion for sustainability. Plausible bounds on starting total harvest rate were 1.7–3.9%, where the range reflects uncertainty due to sampling variation, environmental variation, model selection, and differing levels of risk tolerance. The risk of undesired demographic outcomes (e.g., overharvest) was positively related to harvest rate, management interval, and projected declines in environmental carrying capacity; and negatively related to precision in population data. Results reflect several lines of evidence that the CS subpopulation has been productive in recent years, although it is uncertain how long this will last as sea-ice loss continues. Our methods provide a template for balancing trade-offs among protection, use, research investment, and other factors. Demographic risk assessment and state-dependent management will become increasingly important for harvested species, like polar bears, that exhibit spatiotemporal variation in their response to climate change.

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Publication type Article
Publication Subtype Journal Article
Title Demographic risk assessment for a harvested species threatened by climate change: Polar bears in the Chukchi Sea
Series title Ecological Applications
DOI 10.1002/eap.2461
Volume 31
Issue 8
Year Published 2021
Language English
Publisher Ecological Society of America
Contributing office(s) Alaska Science Center, Coop Res Unit Seattle, Eastern Ecological Science Center
Description e02461, 13 p.
Country Russia, United States
Other Geospatial Chukchi Sea
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