Threats

There are several common threat to polar bears such as climate change and the harmful chemicals that man is releasing to the environment.

Climate change:
Polar bears practice hunting, birth and raising cubs on the ice. 
Polar bears often have to travel hundreds of miles between the icebergs but the trip pool could endanger the lives of the polar bears.Climate change is gradually separating polar bears out of the ice, forcing them to swim farther to find food and shelter

In recent decades, it is expected that increased concentrations of greenhouse gases from the industrial age is by far the major cause for global warming. Although carbon dioxide is only about 20% contribution to the greenhouse effect (water vapor contributes over 50%) but it is a factor causing a rise in global temperature: the amount of CO2 released into the atmosphere increased by a third in the second half of the twentieth century. Thus, as the increase in global temperature, increased carbon dioxide in the atmosphere is undeniable.

Major cause of climate change is due to the increase of physical activities generated by greenhouse gas emissions, the active exploitation of sinks and reservoirs of greenhouse gases such as biomass, forest, marine ecosystems, coastal and other land. Human activities highly contribute to the climate change.

Mercury: 
Scientists have found mercury in polar bears bodies.How does it happened? Mankind released mercury to the ocean,then high levels of mercury is due to the rising seas. When mercury contaminate their water sources, this element will gradually enter the food web. The level of intrusion the higher the level of accumulation also increased. Therefore, when large animals such as the albatross, big fish or seals mercury, poisoning rates are very high.By the time the polar bear eats the seal, the mercury levels could have a lethal effect on the polar bear.