The town of Churchill in Manitoba, Canada, is known as the "Polar Bear Capital of the World," with nearly a thousand bears outnumbering the 800 year-round human residents.
But the town's claim to fame could be in jeopardy if milder winters continue, making nearby Hudson Bay less of a draw for hungry bears.
Every fall, along the bay's shore, polar bears wait for the ice to form so they can hunt seals and build fat reserves. Their annual migration and trek onto the ice is vital for their survival, as their bodies demand a high-fat, high-protein diet to withstand the arctic winter. But because of warmer temperatures, the Canadian waters are freezing later and thawing earlier, diminishing the amount of time these bears have to hunt.
Scientists have calculated that the amount of time that Hudson Bay is covered with ice has been decreasing by one day, every year. In 2012, the bay was ice-free for 222 days. Based on the physiological demands for food and the availability to hunt, scientists have determined that the current polar bear population can survive about 160 days without ice.
Given the data and the prospect that conditions do not change, one of the world's preeminent polar bear experts predicts that two-thirds of the world's polar bear population could disappear in the next fifty years.
Dr. Steve Amstrup, chief scientist with the research organization, Polar Bears International, estimates there are between 20,000 and 25,000 polar bears in the world. The international scientific community has identified 19 subpopulations of polar bears throughout the five arctic countries – Canada, Greenland, Norway/Denmark, Russia and the United States. While their diet primarily restricts them to areas that are heavily populated with ringed and bearded seals, polar bears can migrate thousands of miles during a hunting season making it difficult for researchers to generate population numbers.
Amstrup notes that while extensive historical data does not exist, in 2001 two subpopulations were identified as having a decrease in polar bear numbers, compared to 2009 where eight subpopulation showed a decline. The subpopulation of Western Hudson Bay is among those with the highest recorded decrease in polar bear numbers.
Part of Amstrup's concern about the animal's future is the response by federal policymakers in addressing climate change. In 2011, Canada announced it was withdrawing from the 1997 Kyoto Protocol, requiring countries to meet targeted levels of greenhouse gas reduction. At the time of the announcement, the country's environment minister cited the possibility of multi-billion dollar fines as a factor in the decision, while at the same time leaving open the possibility for future international agreements on greenhouse gas reduction.
But for Amstrup and scientists monitoring the conditions of Hudson Bay, immediately addressing climate change is essential for the future of the polar bear.