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Years of low sea ice conditions has put their lives in jeopardy

Biologists have studied and observed polar bears in Canada's western Hudson Bay for years. Important data has come from this research, such as how long the polar bears spend on the shores of Hudson Bay annually and how much of a decline of ice there is in the bay. Now, researchers have answered the question regarding how long the polar bears have before global warming ends their existence

Biologist Andrew E. Derocher of the University of Alberta, along with Dr. Peter K. Molnar and other colleagues, have found that the polar bear population in western Hudson Bay could die out in approximately 25 to 30 years. 

Derocher and his colleagues came to this conclusion after discovering some other startling data. The polar bears in this area have been losing more than 20 pounds per decade, their body mass has been declining, females have lost 10 percent of their body length, they've been forced to spend an extra week per decade onshore, and the overall population has decreased from 1,200 to 900 in three decades. Most of the population drop occurred over this past decade. In addition, mating habits have changed under recent climatic conditions which could hinder the survival of the polar bears.

"We developed a model for the mating ecology of polar bears," said Molnar. "The model estimates how many females in a population will be able to find a mate during the mating season, and thus get impregnated."

Molnar further explained that male polar bears find mates by tracks in the ice, and when a female is leaving tracks in mating condition, the male will follow. As the climate warms, ice is lost and more time onshore leads to a decrease in body mass and health, which results in less reproduction.

The tip of the iceberg was when projected sea ice declines were observed due to global warming, which led Derocher, Molnar and their colleagues come to the conclusion that polar bears in the western Hudson Bay would be doomed in 25 to 30 years. Polar bears' health depend very much on the time spent on on sea ice hunting seals, and with a decline in sea ice, they cannot hunt and their health is put in jeopardy. Derocher said all it would take is "several straight years of low sea ice conditions -- such as the current year -- which could force the bears onshore for more than five months a year, leading to a sharp decline in in the bears' physical condition and the female's inability to gestate cubs."

Derocher and his colleagues wrote a research paper on their Hudson Bay polar bear population findings, which was published in Biological Conservation. Derocher laid out the best and worst case scenarios for the population based on the data collected from Hudson Bay. 

"The worst-case scenarios are that this population could be gone within the decade," said Derocher. "A more optimistic scenario would say that we'll bounce between good years and bad years for several decades to come. Everything that we can see about the sea ice in western Hudson Bay suggests that it's going to disappear sooner rather than later." 

Some biologists have suggested that the polar bears in this area could be saved by adapting to life on land and eating goose eggs, but Derocher argues that this isn't a stable food source. While polar bears do eat goose eggs, this would only help them out for a day or two of lost time on the sea ice. Also, once polar bears ate all of the goose colony's eggs in the Churchill area, the goose population would die out, and the polar bears would face problems in food shortages on land as well.

This research has led biologists to worry about other polar bear populations around the world such as those in the Davis Strait area between Canada and Greenland and those in the Chukchi Sea between Alaska and Russia. According to Derocher, polar bears in these areas are vulnerable to climate change as well. 

"The first paper I coauthored about this came out in 1993 and at that time I was still under the impression that even though climate change was a concern, it was really going to be for the next generation of biologists -- or perhaps even the one after that -- to deal with the issue," said Derocher. 

"I've been really shocked at the rate of change, and I've probably been even more shocked at the lack of concern of political bodies to deal with this. It's been quite disheartening to watch this lack of interest, and I think it's really unfortunate that people don't understand that we have a limited time to deal with this issue if we want to save the polar bears."

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