Anchorage Daily News

Interior Secretary Dirk Kempthorne hasn't added a U.S. creature to the endangered species list since he took office two years ago. The former Idaho governor has until Thursday to decide on one that could prove troublesome to promising petroleum drilling off Alaska's northern coast and force federal agencies in other states to react to new greenhouse gas emissions.

A federal court in Oakland, Calif., two weeks ago ordered Kempthorne to decide whether to list polar bears as threatened because of global warming's effect on their habitat, the frozen Arctic Ocean.

Polar bears use sea ice for hunting seals, denning and mating. They rely on ice to reach denning areas on shore.

Summer sea ice last year melted to record low levels, receding far beyond the shallow, nurtrient-rich outer continental shelf that supports their main prey, the ringed seal. Polar bears that ride the ice spent more time over less productive, deeper water and faced increased distances from the ice edge to shore if they chose to swim late in the year.

Conservation groups fear continued sea ice loss could reduce fat on polar bears, lower their reproduction rates and cause them to expend more energy -- all precursors to a population crash.

Habitat loss, projected by most climate models to accelerate, was a basis for the Endangered Species Act listing petition submitted by the Center for Biological Diversity and two other conservation groups.

"Polar bears are completely dependent on Arctic sea ice for all of their essential behavior," said Kassie Siegel, the primary author of the petition.

A recovery plan for polar bears could interrupt plans for petroleum exploration and drilling off Alaska's shore.

Also, conservation groups frustrated by the Bush administration's failure to treat greenhouse gases as a pollutant want a listing to force the federal government to curb emissions, the primary cause of Arctic warming and sea ice loss.

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