re: The Earth
Mother nature has a way of dealing with overpopulation. Its usually starvation, some disease from being crowded together, of competition (war). Hopefully we won’t let it come to that.
Some might argue that letting evolution take its course may be a good thing. We are left with a stronger race with a lower population. I disagree. I think our technology has made it so that not only the strong survive.
What we need to do is get humans living in space. If we could move our industry off the Earth, that would help the Earth’s environment.
We could also start reclaiming the Earth’s great deserts, like the Sahara. Then work on terraforming Mars and Venus.