Reduction of sea has made it difficult for polar bears to find food.
While the reduction in sea ice has created economic benefits for some, it has caused serious problems for many species of animals.
By Dr. John J. Hidore
March 1, 2015—In the Arctic Sea, summer sea ice has been retreating from the shore rapidly in the past few decades. In the last few years, the ice has retreated far enough from shore, and thinned enough that the Northwest Passage is open for commercial shipping. This has resulted in considerable economic benefit for the shipping industry—but at the expense of wildlife in the region!
Polar Bears Use the Sea Ice as a Base to Hunt Food
While the reduction in sea ice has created economic benefits for some, it has caused serious problems for many species of animals—one being the polar bear. Polar bears live on the sea ice much of the year and use the sea ice as a base from which to hunt for food. Climate change has caused the ice to retreat further from the coast, making it more difficult for the animals to swim to the ice and back. The Polar bear needs food that is high in fat—and seals provide such a food. However, the population of seals, which is the primary food for polar bears, is declining because the fish population, on which the seals depend, is also declining because of the change in water temperature.
Polar bear cubs are decreasing because of lack of food.
Extinction of the Polar Bear
Polar bears are found across the boundary between the southern limits of sea ice and the northern hemisphere land mass. This area includes Russia, Norway, Greenland, Canada, and the United States. There are more than 15 different groups of polar bear scattered around the arctic sea, and the population numbers for many of these groups is not known, but the total number of bears found in these regions is believed to be declining. Total numbers may be as many as 25,000. The International Union for the Conservation of Nature has listed the polar bear as vulnerable.
Polar Bears of the Beaufort Sea
Three-fourths of the global polar bear population is found in North America. Polar bears of the Beaufort Sea, which is the southern boundary for the bear, have decreased by 40% since the beginning of the 21st Century. Since the southern areas are warming faster and the sea ice is retreating further from shore, it is here that the problem for the polar bear is the worst. The number of Polar bears living in the southern Beaufort Sea dropped from an estimated 1500 in 2001, to only 900 in 2010. In a four year period, from 2003 to 2007, scientists tagged 80 cubs of which only two survived.
Sea Ice: Too Thin and Too Far from Land
Two-thirds of the Northern Alaskan female polar bears are being forced to make their dens on land rather than on the sea ice, which is their normal location. The sea ice has become too thin and too far from land in the winter. The female polar bear has been documented as swimming more than 300 miles from ice to land and many do not survive the long swim. If the Arctic ice continues melting far from shore, it may drive the polar bear to extinction. Projections show that the population could decline by more than 30 percent by 2050. In May of 2006, the World Conservation Union declared the species to have a high risk of extinction in the wild. Worst case scenarios forecast the global population to drop by 2/3 by 2060.
Hudson Bay also harbors a group of bear which is declining. Canadian scientists in 2013 estimated this population was down 25% since 1988. Data indicates the weight of the female polar bear here has dropped approximately 88 pounds and the number of cubs are decreasing and becoming smaller. The western Hudson Bay is now freezing later in the season and melting approximately three week earlier than several decades ago. This has reduced the bear’s hunting season on the ice by several weeks. The critical period for hunting is in the spring when the females are giving birth. Over the hunting season the bears are adding less fat to get them through the winter. Due to increasing malnutrition the group could become extinct by 2050.
Survival of the Polar Bear
Whether the polar bear can survive on food found on land is doubtful. Existing food found along the Arctic coast is not enough to sustain the animals. As an alternate source of marine food, some bears have attached themselves to walrus herds. While they do not attack adult walrus, they may capture their young. Some polar bears are beginning to scavenger the carcasses of dead bear and whales for food.
In 2008, the U.S. listed the polar bear as threatened under the Endangered Species Act.
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