Polar bears are now swimming for kilometres looking for ice because that's where they can hunt their prey without being seen. Many of them drown. Some find land and die later, exhausted and starved. All thanks to the ongoing global temperature increase and the collapse of the northern ice sheets.
According to NOAA, NASA and every single scientist expert in the Arctic, the "sea ice area is now significantly below the level of the 1980s and earlier". As a direct result of the ice shrinking, the population of polar bears has been decreasing for years. The two main reasons are starvation and drowning. Even while they can swim for 100 miles to find new ice hunting grounds, the sheets are becoming farther apart, making swimming dangerous for them.
On top of that, there is less prey available and, since there is less ice, polar bears can't use their camouflage to hunt. And it's only getting worse each year. As a result, polar bears were listed as a threatened species in the United States' Endangered Species Act of May 2008. Biologists are alerting that, given the current weather trends, their survival is doubtful.