Wolfgang...as I understand it, Polar Bears are not normally 'communal' creatures. Each adult needs quite a bit of territory. If they could manage to move their activities to various islands, it would create conflicts for territory, not only with other Polar bears, but also with other carnivores. Also, with major reduction in sea-ice, seal breeding and feeding would be affected, altering hunting & feeding patterns quite a lot.
It would be very hard to predict the results, but it seems to me that it would cause serious realignment of species and habitat....perhaps even in interbreeding that would change 'Polar' bears to something else.

I suppose it is not the most serious aspect of climate change we need to consider, but it represents a lot in cultural terms....and the point right now is how the whole issue is being censored for political purposes, rather than being considered on its merits.