The Cause and Effects of Global Warming on the Polar Bear
Most experts agree that global warming does exist and it is having a devastating effect on the Earth’s climate. A major concern of global warming is the melting of the polar ice caps. Research suggests that global warming is going to greatly impact the survival of the polar bear.
In southern portions of their range, like Hudson Bay, Canada, there is no sea ice during the summer, and the polar bears must live on land until the Bay freezes in the fall, when they can once again hunt on the ice. While they are on land during the summer, the polar bears eat very little or sometimes nothing. In just 20 years the ice-free period in Hudson Bay has increased by an average of 20 days, thus cutting the polar bears' seal hunting season by nearly three weeks. Because the ice is freezing later in the fall, and melting earlier in the spring the bears have a much shorter timeframe in which to hunt during the critical season when seal pups are born. As a result, average bear weight has dropped by 15 percent, causing reproduction rates to decline. The Hudson Bay population is down more than 20 percent. Despite the fact that polar bears are good swimmers there has been an alarming increase of polar bears drowning. Although they are well adapted to water, and can swim hundreds of miles to reach solid land, the distance to reach that land is increasing dramatically as the Arctic ice disappears. It is believed that fewer and smaller ice floes and erratic climate changes have contributed to this situation. Polar bears travel great distances in search of prey, which consists mainly of seals. The most important habitats for polar bears are the edges of pack ice, where currents and wind interact with the ice, forming a continually melting and refreezing matric of ice patches. This is where the greatest seal abundance and accessibility is. Individual bears can travel thousands of miles per year following the seasonal advance and retreat of sea ice.

The Arctic seals depend on Arctic sea ice for survival. During the late winter through early summer, ribbon seals rely on the edge of the sea ice in the Bering and Okhotsk seas off Alaska and Russia as safe habitat for giving birth and as a nursery for their pups. But this winter sea-ice habitat is rapidly disappearing. If current ice-loss trends from global warming continue, the seals are likely facing extinction by the end of the century. The seal’s winter sea-ice habitat is projected to decline by 40 percent by mid-century. Any remaining sea ice will be much thinner and unlikely to last long enough for the seals to finish rearing their pups, leading to a major decline in the seal population. Disturbingly, warming in the Arctic is occurring at a rapid pace that is exceeding the predictions of the most advanced climate models. Summer sea-ice extent in 2007 plummeted to a record minimum, which most climate models forecast would not be reached until 2050.
“With the rapid ice loss in the Arctic and Antarctic regions, many subspecies of seals are currently racing against the ticking clock of climate change. The worldwide status of seal population is alarming. According to the Union of Concerned Scientists, “almost no seal pups, dependent on sea ice, survived in Canada’s Gulf of St. Lawrence during the ice-free years of 1967, 1981, 2000, 2001, and 2002.” The southern hemisphere seal population has been likewise affected by ice loss. Environmental scientists, Dr. Clive McMahon and Dr. Harry Burton of the Australian Antarctic Division, have concluded that warming climate is changing the ocean’s ecology to such a degree that the survival of seals and their young has increasingly become a concern for marine biologists.”[1]
If we don’t make changes to save the polar ice caps, the polar bear will be completely extinct in less than 100 years. Experts believe that they will be completely gone if the temperatures continue to rise due to global warming. It is believed that approximately 30% of the population will be gone within the next 45 years. This means there will be less Polar Bears out there for reproduction. Since polar bears only give birth about once every three to four years, getting efforts in place for them to safely reproduce is important. The mortality rate is 40% that cubs won’t reach their first year mark alive. By ensuring that they can survive though we have a chance to see an increase instead of a decrease in their numbers over that span of time.
"Once climate warming initiates, you get into a self-warming cycle," said Dr. Andrew Derocher, who earned international renown as a polar bear and northern studies expert at the Norwegian Polar Institute in Tromso before returning to the University of Alberta, where he completed his doctorate. "That's why the urgency on the issue for polar bears now."
He believes that it is possible that a warmer climate could possibly improve the polar bear and seal habitats in the short term, especially in higher latitudes where the ice is too thick for seal hunting. But he points out that these areas are small, and will only support a fraction of the bear population.
Derocher feels that Polar bears can tolerate some environmental variation from year to year, foregoing reproduction in any given year if conditions are poor. Derocher says “With too much variation, however, reproduction will fall off dramatically, and populations will quickly decline.” If the polar bears are going to continue to be able to inhabit the Arctic region then their natural habitat needs to be preserved. If global warming continues at this rate it is going to create a very difficult future for the polar bear. They may be able to adapt to some changes, but too many changes will cause a great deal of stress for these bears. Derocher says if global warming continues unchecked, some remnant populations of polar bears may manage to hang on in the high Canadian archipelago or on permanent polar ice at very high latitudes. But the potential for extinction is still a cause for concern: "You don't have to be a polar scientist to see that if you take away all the sea ice, you don't have polar bears any more."[2]

Works Cited 1. http://www.climate.org/topics/ecosystems/seals-battle-climatechange.html 2. http://www.scienceagogo.com/news/20030008220241data_trunc_sys.shtml