If humans wanted to they can kill earth off so that nothing ever lives on it again. Are you saying it's not possible?
Yes I'm sure earth will recover once humans have left. But if we where to make everything extinct then nothing can come to life again.
Nope it's not possible. Human arrogance though makes him think he can. Even if we bombed the all surface of the planet with nuclear weapons some life would still make it through. Not all life in this planet is weak to radiation like humans are you see.
However a scenario like that as virtually no chance in happening not to that extreme. I would be more worried about Yellowstone volcano going off then the idea of humans denting the planet.