title: Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines.
abstract: Loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range. We evaluated the potential response of polar bears to sea-ice declines by (i) calculating generation length (GL) for the species, which determines the timeframe for conservation assessments; (ii) developing a standardized sea-ice metric representing important habitat; and (iii) using statistical models and computer simulation to project changes in the global population under three approaches relating polar bear abundance to sea ice. Mean GL was 11.5 years. Ice-covered days declined in all subpopulation areas during 1979-2014 (median -1.26 days year-1). The estimated probabilities that reductions in the mean global population size of polar bears will be greater than 30%, 50% and 80% over three generations (35-41 years) were 0.71 (range 0.20-0.95), 0.07 (range 0-0.35) and less than 0.01 (range 0-0.02), respectively. According to IUCN Red List reduction thresholds, which provide a common measure of extinction risk across taxa, these results are consistent with listing the species as vulnerable. Our findings support the potential for large declines in polar bear numbers owing to sea-ice loss, and highlight near-term uncertainty in statistical projections as well as the sensitivity of projections to different plausible assumptions.
authors.affiliation: Marine Mammals Management, US Fish and Wildlife Service, Anchorage, AK 99503, USA eric_regehr@fws.gov.
authors.forename: Eric V
authors.identifier: 0000-0003-4487-3105
authors.initials: EV
authors.lastname: Regehr
authors.affiliation: Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA.
authors.forename: Kristin L
authors.identifier: 0000-0002-2787-650X
authors.initials: KL
authors.lastname: Laidre
authors.affiliation: Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: H Resit
authors.initials: HR
authors.lastname: Akçakaya
authors.affiliation: Polar Bears International, Bozeman, MT 59772, USA.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Amstrup
authors.affiliation: Alaska Science Center, US Geological Survey, Anchorage, AK 99508, USA.
authors.forename: Todd C
authors.initials: TC
authors.lastname: Atwood
authors.affiliation: Environment and Climate Change Canada, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Lunn
authors.affiliation: Ontario Ministry of Natural Resources and Forestry, Peterborough, Ontario, Canada K9J 7B8.
authors.forename: Martyn
authors.initials: M
authors.lastname: Obbard
authors.affiliation: Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA.
authors.forename: Harry
authors.initials: H
authors.lastname: Stern
authors.affiliation: Faculty of Environmental Studies, York University, Toronto, Ontario, Canada M3J 1P3.
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Thiemann
authors.affiliation: Natural History Museum, University of Oslo, Oslo 0318, Norway.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Wiig
mesh_terms: D000818:Animals; D001110:Arctic Regions; D057231:Climate Change; D003198:Computer Simulation; D003247:Conservation of Natural Resources / Q000639:trends*; D017753:Ecosystem; D005544:Forecasting; D046448:Ice Cover; D011156:Population Density; D011157:Population Dynamics / Q000639:trends; D001503:Ursidae
keywords: Arctic; climate change; polar bear; population projections; red list; sea ice