All that can be done in that regard is already done.
Hans Rosling summarizes so much better than I possibly could, in his Ted talk.

http://www.youtube.com/watch?feature=player_embedded&v=ezVk1ahRF78

The population explosion is over, the rising numbers are all inertia, and completely unavoidable.

As far as I know, only China successfully restricted population growth. When people have reasonable life expectancy and women get an education, the population restricts its own growth. Improving outcomes in these two respects, in countries which have not yet made the demographic transition, is the key to limiting population growth.

The situation is far from hopeless, because a lot of progress is going on.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}