NOT TOO LATE TO SAVE THE POLAR BEAR

The Polar Bear, Global Warming, and the Endangered Species Act

Polar bears are completely dependent upon Arctic sea-ice habitat for survival. Polar bears need sea ice as a platform from which to hunt ringed seals and other prey, to make seasonal migrations between the sea ice and their terrestrial denning areas, and for other essential behavior such as mating. Unfortunately, the polar bear’s sea-ice habitat is literally melting away. Global warming is impacting the Arctic earlier and more intensely than any other area of the planet. In parts of Alaska and western Canada, winter temperatures have increased by as much as 3.5° C in the past 30 years. Over the next 100 years, under a moderate emissions scenario, annual average temperatures in the Arctic are projected to rise an additional 3-5°C over land and up to 7° C over the oceans.

This rapid observed and projected warming reflected in the devastating melt of the Arctic sea ice, which is highly sensitive to temperature changes. (Figures 1, 2). At 1.63 million square miles, the minimum sea-ice extent on September 16, 2007 was about one million square miles (One million square miles is equal to about the area of Alaska and Texas combined) below the average minimum sea ice extent between 1979 and 2000.

Leading sea ice researchers now believe that the Arctic could be completely ice free in the summer as early as 2030. Climate change in the Arctic has reached a critical threshold, and the future of the ice dependent polar bear is grim. Even short of complete disappearance of sea ice, projected impacts to polar bears from global warming will affect virtually every aspect of the species’ existence. These impacts include a shortening of the hunting season caused by delayed ice formation and earlier ice break-up, resulting in reduced fat stores, deteriorated body condition, and subsequent reduced survival and reproduction; increased distances between the ice’s edge and land, making it more difficult for bears to reach preferred denning areas; increased energetic costs of traveling farther between ice and land and through fragmented sea ice; and reduction in ice-dependant prey such as ringed seals and bearded seals. Global warming will also increase the frequency of human-bear interactions, as greater portions of the Arctic become more accessible to people and as polar bears are forced to spend more time on land waiting for ice formation. More human-bear interactions will almost certainly lead to increased polar bear mortality.

Five of the world’s polar bear populations are now classified as declining, with a 22% decline from 1,194 bears in 1987 to 935 bears in 2004—in Canada’s Western Hudson Bay polar bear population.

Figure 1: Arctic Sea Ice Extent on September 21, 1979 Image source: NASA/Goddard Space Flight Center Scientific Visualization Studio	Figure 2: Arctic Sea Ice Extent on September 14, 2007 Image source: NASA/Goddard Space Flight Center Scientific Visualization Studio

Center for Biological Diversity
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Polar bear image by Thomas D. Mangelsen / Imagesofnaturestock.com
1979 and 2007 Arctic sea ice images courtesy of NASA/Goddard Space Flight Center1979 and 2007 Arctic sea ice images courtesy of NASA/Goddard Space Flight Center