They believe that global warming will wipe out the creatures and only a handful - those in zoos - will remain.
Climate changes are threatening the Arctic ice pack where the bears live and that could disappear by about 2060.
The pack ice is essential to the bears because they cannot survive on dry land.
And the ice is thinning so quickly that bears will be forced to find food on land.
The report, which looks into the bear's future, is due to be published next week by the World Wildlife Fund for Nature.