If it's as bad as they say, we will not be able to adapt enough to survive. End of people. 200 years later, Earth has returned to "balance" and thrives.
So why do they want to stop it?
I always think it's like when you hear someone bemoan how awful man is as a species. Or see one of those movies or Twilight Zone episodes where it's revealed that people really are just plain awful and they're bringing on their own doom. Greedy, selfish, self-involved. All that. James Bond villains who want to rid the Earth of such vermin.
Well - not really. They don't include themselves. The writer of such movies and stories - they don't mean themselves TOO. Other people. Everyone ELSE. Those people over there. I didn't mean *ME*. If the Earth needs a plague to save it - I *will* save a vial of vaccine for *myself* because they all might be evil - but not *ME*.
As Linus van Pelt said (when Lucy ridiculed him for wanting to be a doctor, because he didn't love mankind) "I DO love mankind - it's people I can't stand!". They don't want EVERYONE gone - just the ones they don't want. You know. THOSE guys.
What they'd LIKE is to return the Earth to some pristine, idyllic paradise with SOME people in it. Not enough to destroy the world.
(I don't get the idea that the world without people is some kind of harmonious paradise - life is at war with one another. Smaller creatures eat even smaller creatures - males kill cubs that aren't their own - plants crowd and choke other plants with their branches, vines, tendrils and roots. They are all in competition for survival. It's only in someone's bizarre imagination that the lion lays down with the lamb).
