By Neal Lineback and Mandy Lineback Gritzner, Geography in the NewsTM
Polar Bears on the Run
The world’s polar bears are becoming more and more threatened, not from predation, as they have no natural predators except humans, but from global warming. A book entitled On Thin Ice: The Changing World of the Polar Bear by Richard Ellis maintains that within 100 years the polar bear will disappear from the planet.
Ongoing research, ironically, is describing the polar bear as the “canary in the coal mine,” a reference to the use of canaries in detecting deadly gas in coal mines. As sea ice shrinks in the Arctic Ocean, the polar bear’s natural habitat will diminish, reducing food supply. Thus the polar bears’ loss of habitat and decline are dire predictors many global warming consequences.
The polar bear (Ursus martimus), or “sea bear,” likely evolved about 200,000 years ago from brown bear ancestors. It is native to the high latitudes of the Arctic, including the Arctic Ocean and its adjacent landmasses.
Polar bears are extremely well adapted for survival in the Far North. They have many body characteristics perfect for cold temperatures, including thick blubber (up to 4.5 inches (11.4 cm), two layers of fur and small ears and tail to prevent heat loss. They are well adapted for traveling across ice, snow and open water, and for hunting the seals that make up the majority of their diet. Their white coats offer perfect camouflage against the snow and ice, but their fur also makes the polar bears exceptionally visible when they are on bare soil.
While polar bears are the world’s largest predators on land, they are also the largest bear, sharing that distinction with the omnivorous Kodiak bear of nearly the same size. An adult male polar bear weighs from 775 to 1,500 pounds (350-680 kg), while a female weighs about half that amount.
Many scientists consider the polar bear a “marine mammal” because it spends much of its life at sea. The polar bear prefers to range along the near-shore annual ice that covers the waters over the continental shelf. There in the “Arctic ring of life,” the levels of biological productivity are higher than in the deep waters of the Arctic Ocean.
Areas where sea ice meets water, such as “leads” (temporary stretches of open water in Arctic ice) and “polynyas” (areas of open water surrounded by sea ice) are perfect hunting grounds for the polar bear. Therefore, the bears are found mostly along the perimeter of the polar ice pack, not near the North Pole where the density of seals is low. The United States (Alaska), Canada, Russia, Denmark (Greenland) and Norway (Svalbard) all boast polar bear populations.
As seasons change and storms occur, the areas of water around the margins of the ice appear and disappear. Seals—the polar bear’s major food source—must migrate along with those areas of open water to come to the surface for oxygen. Polar bears, of course, migrate to follow the seal populations.
In some areas, like Hudson Bay and James Bay, the ice melts completely each summer. This forces polar bears to escape to land to wait through the months until the next winter’s freeze.
Because polar bears travel upon the sea ice to hunt, any changes to ice distribution, characteristics or timing profoundly affect the animal. An overwhelming body of research suggests that climatic warming is underway in Arctic areas and that the rate of sea ice melt will increase. If the polar ice cap disappears, the seal breeding grounds will also disappear, leaving the polar bear with nothing to eat, leading to its extinction.
Today, scientists estimate that 20,000-25,000 polar bears still exist. Unfortunately, their numbers not only are threatened by melting ice, but also by industrial pollutants.
Coal-fired power plants located south of the Arctic supply the toxins, including mercury, that ultimately pollute the bears’ bodies. As toxic material travels northward on the wind, it lands either on the water or the land. Polar bears, who are at the top of the Arctic food chain along with killer whales, consume the toxins by eating the animals that have accumulated the toxins. Richard Ellis maintains that polar bears are the most contaminated land animals on earth.
How long does the polar bear have? In his book, Ellis predicts that the Arctic Sea’s summer ice cap will be gone within 50 years and that the polar bear will disappear in about 100 years.
This is a sobering prediction, made even more troubling by the implications for the Arctic peoples who also depend on sea life for sustenance.
And that is Geography in the News.
Sources: GITN 1020, Polar Bears Treading on Thin Ice, Jan. 18, 2010; and Ellis, Richard, On Thin Ice: The Changing World of the Polar Bear Knopf Doubleday Publishing Group, 2010.
Co-authors are Neal Lineback, Appalachian State University Professor Emeritus of Geography, and Geographer Mandy Lineback Gritzner. University News Director Jane Nicholson serves as technical editor. Geography in the NewsTM is solely owned and operated by Neal Lineback for the purpose of providing geographic education to readers worldwide.