"We have the fate of the whole (biological) world in our hands!"
Au contraire. The rest of the biological world has the deciding vote.
How long do you imagine that we can continue to burn out our biological support structure from beneath our feet, until we ourselves are expunged?
Michael Pollan observed that Nature doesnt really care if a few hundred square miles is overrun by kudzu for a few hundred years. He was speaking in a local context, but in a larger sense, Nature doesnt care if we have a Canfield ocean for a few million years. She takes every bet. She'll just explore sulphur pathways (again) for a while. And come up with biologies even more interesting no doubt ... which do not include us.