There are fewer than 25,000 polar bears left in the wild, according to the nonprofit organization Polar Bears International. Near the southern Beaufort Sea, the population has dropped about 40 percent between 2001 to 2010, from 1,500 to 900 bears.
The chief threat to the polar bear is the loss of its sea ice habitat due to global warming. The time bears have on the ice is their best season for hunting seals and finding fish. In this way, they restore their body fat and fitness. But this crucial time for storing up energy for the warm season when there is less ice and little available food is becoming dangerously limited.
As the periods without food lengthen, the overall body condition of polar bears declines. This is particularly serious for bears that are pregnant or nursing young, and for the cubs themselves. In Hudson Bay, scientists have found the main cause of death in cubs to be either lack of food or lack of fat on nursing mothers.
Rising global temperatures have led to longer annual ice melts in the summer, and incomplete re-freezes in the winter. This makes it harder for the polar bears to find food, since they depend on ice sheets to hunt seals that also use them for rearing pups.
Greenhouse gases (GHGs) in the atmosphere is causing the ice to melt in the Arctic. GHGs act like a blanket that keeps the earth warm. This protective blanket helps make our planet habitable. But over the past 200 years, humans have greatly increased the level of GHGs in the atmosphere by burning fossil fuels like oil and coal. This is like throwing on a second blanket, causing temperatures to rise.
Other factors such as deforestation have added to the problem. Trees soak up carbon dioxide (CO2), one of the greenhouse gases, from the air. Fewer trees, especially in the tropics, means less CO2 is removed from the atmosphere.
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