Since banning religion is not going to work as those holding the power will not relinquish it, the onus is on the population becoming aware of the control that is forced onto them.

If a god (s) made the Earth, then slowly destroying the Earth MUST be a sin. This message would have to be incorporated into the mantra of the religious leaders.
Unfortunately the time it takes to plant such a message would make the whole exercise too late in acquiring its goals.

Perhaps economic incentives are the way ahead. Products from countries with high birth rates should maybe have higher import taxes or be banned altogether.