The Earth is not anywhere near overpopulated. We produce far more food than we need. The suffering and such is created by humanity's greed. We throw away food rather than give it to the poor. Besides, if we just gave food to those that are starving to death, that would make us communists!

Likewise, the horrible state that the Earth is in is due to the actions of people, not their number. We could easily support more than double our population if we lived in a smarter manner.

Work on teaching people to live in a more sustainable manner, rather than convincing them they should end their hereditary line for the good of humanity.