Gov. Sarah Palin and other Alaska elected officials fear a listing will cripple oil and gas development in prime polar bear habitat off the state's northern and northwestern coasts.
Palin argued Wednesday that there is not enough evidence to support a listing. Polar bears are well-managed and their population has dramatically increased over 30 years as a result of conservation, she said.
Climate models that predict continued loss of sea ice, the main habitat of polar bears, during summers are unreliable, said Palin, a Republican.
The announcement drew a strong response from the primary author of the listing petition.
"She's either grossly misinformed or intentionally misleading, and both are unbecoming," said Kassie Siegel of the Center for Biological Diversity. "Alaska deserves better."
Siegel said it was unconscionable for Palin to ignore overwhelming evidence of global warming's threat to sea ice, the polar bear's habitat.
"Even the Bush administration can't deny the reality of global warming," she said. "The governor is aligning herself and the state of Alaska with the most discredited, fringe, extreme viewpoints by denying this."
As marine mammals, polar bears are regulated by the federal government, not the state. U.S. Interior Secretary Dirk Kempthorne last week made the listing decision and said it was based on three findings.
"First, sea ice is vital to polar bear survival. Second, the polar bear's sea-ice habitat has dramatically melted in recent decades. Third, computer models suggest sea ice is likely to further recede in the future," he said.
Summer sea ice last year shrank to a record low, about 1.65 million square miles, nearly 40 percent less than the long-term average between 1979 and 2000.
Polar bears rely on sea ice for hunting ringed seals. In recent years, summer sea ice has receded far beyond the relatively shallow, biologically rich waters of the outer continental shelf, giving polar bears less time in prime feeding areas.
The bear's numbers rebounded after the 1970s, but conservation groups contend that was in response to measures taken to stop over-hunting.
Polar bear researchers fear recent effects of the loss of sea ice on Alaska polar bear populations. A 2006 study by the U.S. Geological Survey concluded that far fewer polar bear cubs in the Beaufort Sea were surviving and that adult males weighed less and had smaller skulls than those captured and measured two decades previously - trends similar to observations in Canada's western Hudson Bay before a population drop.
A U.S. Geological Survey study completed last year as part of the petition process predicted polar bears in Alaska could be wiped out by 2050.
Kempthorne said last week he considered every point Palin made, and rejected them.