Animals can't adapt as fast as we're changing things, there are not many places they can go, and it's nearly everything, not just polar bears. Recent studies have found that 58 percent of the global wildlife population vanished in the last 50 years. In the last 20 years we have converted 10% of the world’s wilderness to our own use, with only 23% of the world’s land area remaining as wilderness today. In my lifetime many common and widespread American songbird populations have declined by 50 to 80 percent while numerous woodlands and rural areas, including the one I grew up in, became nothing but housing developments and shopping malls. I don't think any of this will stop and most species that aren't useful to humans (we'll save cows and chickens) end up extinct. Even so, we ought to at least realize the consequences of what we're doing.
This line of thought has so many problems. First, we are animals, right? Evolved just like all the rest. There are limited resources. We grow, others decline. If evolution is a fact and it is also a fact that it was unguided then there is nothing morally wrong with us dominating the globe to propagate our species. Survival of the fittest. We are stronger. We win. For now.
Second, we only want to talk about polar bears and animals that are furry and cute. Pretty trees and woodlands. That is a fetish. It is a desire. It has nothing to do with the evolution of life on the planet. In a world view in which all this happened by accident a slug has no more or less value than a polar bear. Just because we 'like' polar bears is hardly cause to buck the evolutionary order. From that standpoint we are only obligated, evolutionarily, to preserve that which preserves us.
Third, there is no evidence that human expansion, global warming or anything else has produced less
life on this planet. Bacteria are by far and away the most successful life form. They are doing just fine and in great diversity. Sure, we can't see them, they don't have big sad eyes, but they are life and they are thriving.
Fourth, so much of the climate argument hinges on having things a certain way, typically the way they are now, or were 20 years ago. Why? Things change. If we are changing them, so what?
So if you want to make an argument for the preservation of certain species or some imaginary status quo, climate science is not your ally. In fact, science in general is your enemy. Science doesn't care what you or I want or desire. It can't and shouldn't. To justify some human obligation to preserving and conserving you will have to look somewhere other than science because when the last polar bear finally dies it will have a net impact of just about ZERO on virtually the entire human population. It will be an evolutionary event of virtually no importance whatsoever.