Polar Bears: Proposed Listing Under the Endangered Species Act
Publication Date: April 2008
Publisher(s): Library of Congress. Congressional Research Service
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, while the remaining third have insufficient data available to estimate population trends and their status has not been assessed. Two of these polar bear populations occur within U.S. jurisdiction.
Polar bears are affected by climate change, contaminants, and subsistence and sport hunting. Environmental organizations have voiced public concern that polar bears were threatened by climate change. Scientists have confirmed that, in recent decades, the extent of Arctic sea ice has declined significantly as the result of climate warming: annual ice break-up in many areas is occurring earlier and freeze-up later, Arctic sea ice is experiencing a continuing decline that cannot easily be reversed, and some models project that Arctic sea ice will disappear completely by the second half of this century. Three main groups of contaminants are implicated as potentially threatening polar bears -- petroleum hydrocarbons, persistent organic pollutants, and heavy metals. The United States allows limited subsistence harvest of polar bears by Alaska Natives. In Canada, Native hunters are permitted to allocate a limited portion of the subsistence harvest to sport hunters. Under 1994 amendments to the MMPA, U.S. citizens may obtain permits to import sport-harvested polar bear trophies from Canada.
The Fish and Wildlife Service (FWS) has proposed listing polar bears as a threatened species under ESA, acknowledging the increasing threats to their existence. The FWS listing decision must be based solely on the best available scientific and commercial information regarding five factors: habitat destruction, overutilization, disease or predation, inadequacy of other regulatory mechanisms, and other natural or manmade factors.
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.