Polar bears have been endangered for years, but a new study finds that without a decrease in greenhouse gas emission, almost all polar bears will die by 2100.

Dr. Steven Amstrup is the chief scientist at Polar Bears International, an adjunct professor at the University of Wyoming and an author of the paper. He said they used models to measure how much polar bears need to eat to survive and compared that to how much food is available to them.

Seals, a main source of food, don't hang out on land, and polar bears are not fast enough to catch them while swimming, so sea ice is an essential spot for polar bears to find food, Amstrup said.

"Polar bears have evolved for perhaps a million years to catch seals on the surface of the sea ice," he said. "If the sea ice is threatened, the polar bear's dinner plate is essentially threatened."

A warming Earth means less sea ice, but Amstrup said there is another problem.

"It probably takes about 25 years for sea ice to stabilize after we stabilize atmospheric concentrations of greenhouse gases," said Amstrup. "If we want to save polar bears, we need to act now."

Assuming some reduction in greenhouse gases, Amstrup said more polar bears will survive, but overall the population will decline in the years to come.

Have a question about this story? Please contact the reporter, Ashley Piccone, at apiccone@uwyo.edu.