The global warming is the major cause of glaciers melting. The polar bears may reduce 2/3 by 2050 and polar bears in Alaska will extinct. Fish and wildlife service of US suggested listing polar bears as endangered species in "Endangered Species Law" in January 2007. Polar bears hunt seals on ice. However, the melting by global warming may threat polar bear's living area.

US scientists found 4 polar bear died by drowning in Beaufort Bay in 2004. This is a real taunt for polar bears, who were named as swimming master and the traveller on the floating ice.

Scientists of Minerals Management Service of United States found the 9 polar bears when they were exploring the Chukchi Sea (northwest of Alaska) by taking helicopter. Scientists found that the 9 polar bears were swimming in a broad sea. The farthest bear is about 60 miles from the coast. Scientists guessed that those bears were floating on an ice and they were heading the land or another water. However, satellite camera showed the sea ice had disappeared. It meant that those bears also faced the challenges of living and they might be drowning to death too.

Polar bear is not aquatic animal. Sea ice is its home. It is possible for polar bears to swim 40 to 50 kilometers. But it will be challenging for them to swim 50 to 100 kilometers and there is a high risk of drowning. So the cause of the drowning is the distance from one sea ice is too far for them to swim to another. The long journey of hunting makes them exhausted, temperature dropped, and immunity reduced rapidly. It is even more dangerous for bears when storm came.

Scientists think it could be a normal phenomenon in arctic region. In the recent 20 years, more and more polar bears have to come a long way to hunt enough food due to the glaciers melting. The death of polar bears could rise significantly if the ice in arctic area is continuously melting down.

The researchers of wilding animals and plants found the new evidence that polar bear is facing another threat which is the chemical pollutions. Those chemicals are toxic chemicals used to reduce the flammability of sofa, clothing and carpet. A group of scientists together to warn that there polar bear is becoming hermaphrodite. They found PBDEs in polar bear's adipose tissue, particularly those living in east Greenland.

Evidence shows that PBDEs is the major cause of polar bear's hermaphrodite. There is one polar bear with hermaphrodite for every 50 polar bears.

Collin Butterfield, the leader of WWF said: " Arctic region is now becoming the recycle place of chemicals which is harming the wild animals in arctic region." Those chemicals are mainly from United States and west European countries. They are travelling by stream and wind to arctic region and they stay and eventually become part of the food chain. Polar bears are the major victim.

The climate changes threat the living area of polar bears but it is always not late to take action and put efforts. Followings are some ways to prevent greenhouse effect.