Polar bears are considered threatened because their population is declining due to habitat loss. However, as of 2015 they are not considered endangered by any major country or organization.
The United States lists polar bears as threatened, and they are a species of special concern in Canada. The International Union for Conservation of Nature considers them a vulnerable species. This means that scientists and wildlife groups are still working to try to prevent further population decline, but polar bears are not yet in danger of extinction.
Unlike most animals that experience habitat loss, polar bears are largely not affected by human settlement in their territory. Instead, the main threat to polar bears comes from climate change. Polar bears prey almost exclusively on seals, which live on and around arctic sea ice. Warmer arctic temperatures cause that ice to disappear for longer periods of time, which means that polar bears are forced to spend months unable to hunt effectively.
These long periods of fasting cause the bears to lose weight and make it harder for females to carry cubs. Cubs that are born are less likely to survive to adulthood, both due to malnutrition and because adult males are more likely to kill and eat them. When the ice does form, it forms further away from the shore and some weakened bears die attempting to swim to it.