[C4stor]

The planet has never been, is not and probably won't be in any near future in peril. Humanity is. Humans disappearing is the concern of ecology. The planet will adapt just fine with or without us, and species disappearing will be replaced in time by new ones.

Not having children is not effective at perpetuating the human race, and thus not usually considered as an ecological solution.

That being said, you don't have to have children to be an ecologist either, but you certainly should realise that your efforts are directed towards future humans, not towards the planet which does just fine anyway.