The formal notice filed by the Center for Biological Diversity, the Natural Resources Defense Council and Greenpeace is a necessary step before a lawsuit is filed. The notice cited a missed deadline by the federal agencies and officials in Washington on whether polar bears will be listed.
"The science confirms that the polar bear is endangered, but the Bush administration continues to downplay the danger of global warming and delay any action to address the issue," said Kert Davies, research director at Greenpeace USA.
U.S. Fish and Wildlife Service Director Dale Hall said earlier this week that the Wednesday deadline would be missed in part because of the complexity of the issue. The agency has never declared a species threatened or endangered because of climate change and the research effort has been taxing and challenging, he said.
Hall said the agency hoped to have a recommendation within weeks. Interior Secretary Dirk Kempthorne last January had proposed listing polar bears as threatened, and the Endangered Species Act calls for a final decision one year later.
The conservation groups said delays in listing other species have been used to rewrite conclusions of federal scientists.
"Endangered Species Act listing decisions must be based only on science, and the scientists have finished their work on the polar bear listing," said Kassie Siegel of the Center for Biological Diversity.
Polar bears are especially vulnerable to global warming because they spend most of their lives on sea ice.
Summer 2007 set a record low for sea ice in the Arctic with just 1.65 million square miles, according to the National Snow and Ice Data Center at the University of Colorado. That's nearly 40 percent less ice than the long-term average between 1979 and 2000.
In September, the U.S. Geological Survey issued a report concluding that two-thirds of the world's polar bears, including the entire population in Alaska, will be killed off by 2050 because of the thinning ice.
"Endangered" means a species is in danger of extinction throughout all or a significant portion of its range. "Threatened" is one step less serious, a category that means a species is likely to become endangered.
Listing polar bears as threatened could trigger limits on development, particularly oil and gas exploration and production, that could harm the animals.