Polar bears are endangered because of global warming, which negatively affects their natural habitat. Other threats to the polar bear population are pollution, poaching and unregulated hunting.
The U.S. Endangered Species Act listed polar bears as a species threatened by extinction due to global warming in 2008. Polar bears live in areas where the oceans freeze, and their diet consists primarily of seals. They hunt by waiting for a seal to come to the surface of the water to breathe and then pulling the seal up to feed. Global warming increases the temperature of the world's oceans, which causes the oceans to freeze for shorter periods of time.
As a result, polar bears fast for much longer, sometimes for months. The lack of food has caused weight loss for some polar bears. It can also cause them to have fewer cubs, and it reduces the likelihood of polar bear cubs reaching adulthood. Less ice also increases the distance polar bears have to swim, which increases their chance of drowning, particularly for cubs. In addition, the remaining sea ice covers areas with fewer seals.
As of 2008, the polar bear population was estimated at 20,000 to 25,000. There are 19 subpopulations of polar bears; four populations were declining, while five were stable and one was increasing. There's insufficient data about the other populations.