Here is a little story from the movie 'Into the Arctic": "A Polar Bear swam for 9 days without stopping, just so she could find ice land. She had a cub, it sadly didn't make it but luckily the mother did. They were looking for a new home because in their old home all the ice had melted. Many Polar Bears have to do that. Some make it safely, but for others it can be a swim to nowhere."
The reason the ice is melting is because of humans, how we use heaps of brown coal and petrol.