In 8000 B.C., only 5 million people were alive—roughly the population of today’s Papua New Guinea. Overuse of the world’s natural resources was hardly an issue. Now some 6 billion mouths must be fed and bodies clothed and housed. Misuse or depletion of the Earth’s treasures to meet those needs, for example unsustainable logging, poor farming practices, and overfishing, threatens human life and health around the world.

Industrialized countries in the past have done their share of plundering and polluting. But today most such problems occur in developing countries commonly called the Third World, which also happen to be the areas of greatest population growth.

According to the United Nations, population increases have slowed or even stopped in Europe, North America, and Japan. Nevertheless, global population continues to rise at a rate of roughly 78 million people per year. Most of the growth is taking place in sub-Saharan Africa and parts of South and Western Asia—areas least able to afford more people. Not coincidentally, the same places are plagued by deforestation and other unsustainable exploitation of natural resources.