I totally disagree that overpopulation is the worlds biggest problem.
A far greater problem is that a small fraction of the world's population consome most of the world's resources and thus the worlds food. There is enough food produced in the world every year to feed everyone on the planet, but the poorest cannot afford it.
Most of the countries where hunger is widespread are actually net food exporters, they export to the rich countries that can pay more for their food as animal feed than the poor can afford to spend to consume it themselves.
The "new green revolution" stuff is bunk. If we produced more food there would just be a slightly larger group at the top eating luxury food items while the same poor were hungry.
If everyone in the world had the same consumption footprint of those in the US, the sustainable population of the planet would probably be less than half of what it is now. Who wants to tell the other half?
Read: World Hunger 10 myths by Lappe,Collins,Rosset
The impression I've gotten is that much 3rd world hunger is politically caused. One side in a conflict causes a famine for the other side by destroying crops and blocking food aid.
The well intentioned food aid givaways destroy the market for locally grown crops, put local farmers out of business, and make the problem worse the next year.
President Bush proposed buying food for food aid from places near the recipient that produce a surplus, thus stimulating local food production. Congress shot him down. US food aid by law must be US grown. It's yet another agricultural subsidy.