Look at the bark of a redwood, and you see moss. If you peer beneath the bits and pieces of the moss, you'll see toads, small insects, a whole host of life that prospers in that miniature environment. A lumberman will look at a forest and see so many board feet of lumber. I see a living city.
For humans, the Arctic is a harshly inhospitable place, but the conditions there are precisely what polar bears require to survive - and thrive. 'Harsh' to us is 'home' for them. Take away the ice and snow, increase the temperature by even a little, and the realm that makes their lives possible literally melts away.