On December 22, 2010, the Department of Justice filed a supplemental brief (PDF) in the United States District Court for the District of Columbia explaining the guidelines used by the Fish and Wildlife Service (FWS) in deciding if a species should be listed as threatened or endangered under the Endangered Species Act (ESA).  The brief was filed in response to the court’s request for a further explanation (PDF) regarding why FWS listed the polar bear as a threatened, and not an endangered, species.  Environmental groups had filed suit arguing the polar bear should be listed as endangered.  Center for Biological Diversity v. Salazar, No. 1:08-cv-2133 (D.D.C.).  The federal government’s brief attached an explanation and analysis prepared by FWS.  In its memorandum, FWS said the ESA does not provide any quantitative measures for distinguishing between species that are threatened or endangered but FWS has generally relied on four criteria to determine whether a species qualifies as endangered.  The four criteria are: (1) the species is facing a catastrophic threat with an imminent and certain risk of extinction, (2) due to limited range or population size the species is vulnerable to extinction, (3) a species that was previously widespread has been reduced to critically low numbers or restricted ranges, and (4) a species that is still widespread has suffered ongoing reductions in its numbers or range as a result of factors that have not been abated.  FWS then stated the guidance provided by these four factors is not binding because listing determinations also require consideration of individual species characteristics.  As to the polar bear, FWS’ memorandum argued it is not endangered because it is not currently on the brink of extinction since its present condition is stable or increasing in most of the populations for which data is available, and declining slightly in a minority of such populations.  “Overall, both its range and its numbers were relatively constant.”  The Plaintiffs have until January 18 to file a responsive brief and the court will decide the case thereafter.