A: No that's not obvious at all. B: Even if everyone cut their birth rate instantly it would be 100 years before there would be much change. (Think about how l

A: No that's not obvious at all. B: Even if everyone cut their birth rate instantly it would be 100 years before there would be much change. (Think about how long people live and the birthrate is never going to actually be zero.) So even if that was the problem, which it's not, it's not solvable by any method that has to do with reducing the number of humans. Only a new energy source can solve this, which makes population increase a completely pointless thing to discuss.