The fundamental premise is not that extinction is bad, but that extinction we cause is bad. If a fox tramples your neighbor's garden, that's too bad. If you trample your neighbor's garden, you should fix it.
The trouble is, that at the current state of science and technology we can not engineer and control ecosystems. We can not even model ecosystems. As a result we are breaking things and we even have no idea how badly we are breaking things when we are extracting resources. Like when we are turning diverse ecologies into monocultures, when forests are being turned into these 'beautiful' fields of golden wheat.
It does NOT have to be that way. There is no natural law that says that it is necessary to destroy diversity if one wants to grow food or extract resources. It is just that our technology is very primitive and that's the only way we've been able to do it so far. With right technology one can have it both ways. But we don't have it. Not yet.
And meanwhile, well. Conservation, common sense and minimizing our damage to the ecology is probably a best that we can do...
There's a very real choice about how we want to change the environment of the earth, but lets not couch it in meaningless terms like natural vs. unnatural.
Hunter gatherer societies are no more natural/unnatural than cities.
As for the line between human actors vs. non-human actors... when it comes to players in the ecosystem, humans are simply overpowered. That is the root of the problem. Nature has struck a balance in most places, and the ecosystem shifts slowly because everything is close to balance. This gives the other players in the system time to react. Humans are very, very good at destroying balance, so we often warrant special consideration.
Think about your history. The only other actors that brought about the destruction of habitats, ecosystems, and species in as short a time and as great of numbers as humans are natural disasters.
Thank you for describing what I was trying to say much more elegantly. :)
So, given that scenario, I think the better question to ask is, what benefit would we, as humans, get from a return to a cooler Earth? IMO wildlife will take care of itself: adapt, die off, etc. the same way it always has. BUT, I think that too often the focus is put on sad-looking animals and melted snowcaps, which makes it seem like global warming is just an "environmentalist" issue rather than a serious threat to human life.
The ongoing massive extinction event driven by human activity is a real thing. Do you want to live in a world where the only animals alive are ones that humans raise as livestock, or that thrive amongst humans? Nothing but pigs, chickens, pigeons, sparrows, cockroaches, bass and such. Sounds awfully grim to me, but without serious efforts towards preserving wildlife, this is precisely what the future holds.
And it is not that sad. Well designed ecologies can be diverse and beautiful. Even more diverse and beautiful than naturally evolved once.
No penguins in the Arctic, no polar bears in the Antarctic; they have little-to-no bearing on each others population (even indirectly via seal populations). You could've chosen a better example.
Also, before someone posts a link to "that" article, let me say in advance it was written by an intern based on interviews that (in my opinion) suggest exactly the opposite of what the writer concludes.
Ticks are another matter. While birds will eat them, no species that I know of depends on them for its diet. We probably can safely eradicate ticks.