The New York Times Room for Debate posted this question:
Do we still need to worry about Paul Ehrlich's predictions of an overcrowded planet?

Jack Goldstone provided the following response:
Overall, global population growth has slowed tremendously. In places such as Europe and East Asia, the biggest concern for the future is the decline of the working age population, not overall growth. Yet in some regions population is still growing almost as fast as when Paul Ehrlich first raised his alarm, and with still-frightening consequences.

To be sure, population itself is not necessarily a problem. Some of the richest places on earth, such as the Netherlands and Japan, are among the most densely populated. But risks of violent conflict rise when a surging youth population cannot find productive employment, and when a country lacks the resource cushion and quality of government to respond to intermittent crises.

Today, population growth is most rapid in precisely such places, mainly in sub-Saharan Africa and the Middle East.

In countries such as Nigeria, Tanzania and Uganda, women still have from 5 to 6 children, on average, while in conflict-torn countries such as Yemen, Iraq, and Afghanistan, they are still having an average of 4 children during their lifetimes.

In sub-Saharan Africa fertility rates have remained stubbornly high despite two decades of reasonable income growth and rapid urbanization. The key missing factor seems to be secondary education for women, which only a minority in that region have completed. Women who leave school before age 17 remain vulnerable to early marriage, and are less likely to take advantage of modern contraception, leading to larger families.

Regions with very large youth cohorts are historically far more prone to violence than older populations, and high fertility rates are a formula for maintaining very young populations. Only when fertility falls and investments in each child start to rise do societies appear to get on track for political stability and sustained growth in per capita incomes.

Much of sub-Saharan Africa and the Middle East remains far from being on that track today. Moreover, an ever-greater proportion of the world’s children are growing up in these regions. Roughly 25 percent of the world’s children are in Africa today; by mid-century it will be 40 percent. Unless population growth in these regions slows to allow education and investment to catch up with surging youth cohorts, the prospects for long-term stability and prosperity in Africa and the Middle East will remain dim.