Last week, the Interior Department announced its decision to list the polar bear (Ursus maritimus) as a "threatened species" under the Endangered Species Act due to the expected loss of polar bear habitat, specifically arctic sea ice, due to global warming. The listing decision and other related documents are available here. This is the first time a species has been listed under the ESA due to climate change, but it might not be the last. More significantly, the polar bear listing could become a powerful weapon for environmental groups seeking more stringent controls on greenhouse gas emissions, as I discuss in this NRO column.