Hunting
Since the 14th century, Polar bears have been hunted for their fur. As the years go on, the technology get better and better, hunters started using more inhumane ways of killing Polar bears and also other animals. Like in the early 20th century, when hunters used snowmobiles, icebreakers and airplanes to hunt polar bears.
Global Warming
Pollution mainly from human activities is causing the world to temperature increases as years go on. Oceans on Earth absorbs much of the heat energy that enter the Earth, meaning the water gets warmer and warmer. With the warm water, ice in the Arctic are starting to melt away. This is the main threat to the population of polar bears. Unlike seals, or walruses, who can stay in water for long periods of time. Polar bears can only stay in water for a limited period of time. So if the ice melts away, the polar bears in the region will slowly drown to death as they get tired of swimming. The ones that do manage to not drown will have a very hard time finding food because polar bears hunt on ice, eventually leading to starvation. Some polar bears maybe able to adapt the the warmer climate and change their way of living, but as they do that, they might disrupt other ecosystems.