This may be true but it also assumes idealism that everyone will be open to being a good steward of the planet. The way I think about it, lower population is sort of a buffer against an inevitable portion of the population who, no matter how direct and obvious the impact of climate change is, can't be convinced to help society. And unfortunately, at the time of having kids you can do everything you can to teach them to be interested in helping the planet but they still might not, and that would come with a huge amount of guilt in my case.