The Iucn Red List of Threatened Speciestm

Polar Bears (Ursus maritimus) are facing a range of threats that might impact their future population status (see section Threats below). The IUCN Polar Bear Specialist Group (PBSG) regards loss of sea-ice habitat due to climate warming as the most serious threat to future Polar Bear survival. We therefore based our Red List assessment on this threat factor only, recognizing that sea-ice conditions may not serve as a proxy for all environmental changes that could impact Polar Bears (e.g., changes in prey populations) and that secondary factors or potential threats could impact Polar Bears as well, particularly in the absence of management and mitigation (Amstrup et al. 2008, 2010; Atwood et al. 2015). A variety of methods exist to evaluate the effects of environmental change on population ecology (Sutherland 2006). For Polar Bears, several methods have been used evaluate the potential effects of sea-ice loss due to climate change, including structured elicitation of expert opinion through the Delphi method (O’Neill et al. 2008); Bayesian Networks to evaluate the potential effects of forecasted sea-ice extent and multiple qualitative stressors (e.g., Amstrup et al. 2007, 2008, 2010; Atwood et al. 2015); demographic projections or viability analysis using single-population models (e.g., Taylor et al. 2005, Lunn et al. 2014, Regehr et al. 2015); and mechanistic models describing vital rates as a function of environmental conditions or energetic factors for a single subpopulation (e.g., Molnar et al. 2010, Robbins et al. 2012b). To date, no analysis has used all available data on abundance for the 19 Polar Bear subpopulations (Figure 1; PBSG 2015) to evaluate the future status of the species as a function of estimated relationships between abundance and sea-ice conditions.