"The proposed listing of polar bears as threatened under the Endangered Species Act (ESA; 16 U.S.C. §§1531 et seq.) highlights the intersection of two significant issues currently before Congress -- climate change and species protection. According to the ESA, this listing decision rests solely on an interpretation of the best available scientific understanding of the species and how it may be affected by changes in its habitat. Polar bears depend on Arctic sea ice, which most scientists acknowledge will be affected by climate warming causing, at minimum, an earlier annual or seasonal thaw and a later freeze of coastal sea ice. Globally, less than one-third of the 19 known or recognized polar bear populations are declining, more than one-third are increasing or stable. The remaining third have insufficient data available to estimate population trends and their status has not been assessed. Two polar bear populations occur within U.S. jurisdiction. […] Controversy exists over how great a threat the changing climate might be to polar bears and whether they might be able to adapt to these changing conditions. Some point out that polar bears today are not coping with changing climate alone, but also face a host of other human-induced factors -- including shipping, oil and gas exploration, contaminants, and reduced prey populations -- that compound the threat to their continued existence. There is also considerable uncertainty in estimates of polar bear population numbers and trends as well as in our understanding of polar bear habitat."
CRS Report for Congress, RL33941