Taking things off the planet can be even more dangerous.
Imagine a ball revolving around another ball, u add or subtract from it`s mass, and the distance between the 2 balls will change.
A simple term to say that the earth within it`s atmostphere is a closed system. It`s weight is constant, apart from the things that drop into the atmosphere from outside.
U change the weight of the closed earth system and it`s orbit will change.
Similarly, if 1 half of the earth contains over half of it`s population, the shape of the earth changes. Instead of a ball revolving, you can picture u`r tennis ball spinning with a bit of chewing gum stuck to it.
All these things can change the way the earth rotates about the sun, which can change alot of things climate wize.
It`s also mankind`s arrogance to think that the earth is theirs. The lifespan of mankind as a whole is but a finite part of it`s history. It`ll be here long before the race has gone, barring anything catastrophic. And the likes of the ant and coc-roach will outlive the fittest of us.
A coc-roach can survive in u`r neuclear waste