The U.S. Geological Survey, the Interior Department’s research arm, said updated scientific models don’t bode well for polar bear populations across the world, especially in Alaska, the only state in the nation with the white bears.
The report released this week is part of the U.S. Fish and Wildlife Service’s recovery plan for the polar bear. It is expected to be published Thursday in the Federal Register.
Greenhouse gases are blamed for the climate warming that’s reducing the polar bear’s summer sea ice habitat.
The effects of diminished sea ice will lead to population declines throughout the century. Scientists saw no rebound in population numbers in the projections that stretched to the year 2100.
The scientific models attempted to predict the effects on polar bear populations under two scenarios: one in which greenhouse gas emissions stabilized, and the other in which they continued unabated.
Under either scenario, the bears in the Alaska, Russia and Norway group — with an estimated population of about 8,500 — would start to be affected in either 2025 or 2030, said lead author Todd Atwood, an Alaska-based USGS research wildlife biologist.
He said the main reason is this part of the Arctic has suffered some of the most dramatic declines in summer sea ice.
Polar bears feed primarily on seals and use sea ice for feeding, mating and giving birth. When the sea ice retreats in the summer, polar bears are forced to land. A study earlier this year found the land-based food would not help a polar bear adapt to the loss of sea ice. The Office of Naval Research said the past eight years have had the eight lowest amounts of summer sea ice on record.
The USGS didn’t predict specific number declines and instead projected whether a population would see a decreased or a greatly decreased population.
“That’s not to say that we’ll lose polar bears completely out of the area, but we think that they’ll be at a greatly decreased distribution than what they currently are,” Atwood said.
Polar bears in Canada and Greenland also could see dramatic population drops by 2050. Bears in the high Canadian Arctic fared the best in the two scientific models. They saw a “greatly decreased” population only under the worst-case scenario.
“Polar bears are in big trouble,” said Rebecca Noblin, Alaska director for the Center for Biological Diversity. “There are other steps we can take to slow the decline of polar bears, but in the long run, the only way to save polar bears in the Arctic is to reduce greenhouse gas emissions.”
The Center for Biological Diversity originally petitioned for polar bears to be listed as threatened under the Endangered Species Act. In 2008, the species became the first to be listed because of global warming.
This story has been corrected to show the name of the organization that petitioned for polar bears to be listed as threatened is the Center for Biological Diversity.