title: Endangered species. U.S. weighs protection for polar bears.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pennisi
mesh_terms: D000818:Animals; D001110:Arctic Regions; D044822:Biodiversity; D017753:Ecosystem; D053476:Extinction, Biological; D017752:Greenhouse Effect; D046448:Ice Cover; D011156:Population Density; D014481:United States; D037041:United States Government Agencies; D001503:Ursidae