His best-selling 1968 book, which forecast global famines, made him a leader of the environmental movement. But he faced criticism when his predictions proved premature.

Paul Ehrlich, famed ecologist and controversial author of The Population Bomb, died at 93 years old on March 13.

What if the challenge for humanity's future is not too many people on a crowded planet, but too few people to sustain the progress that the world needs? Most people on Earth today live in a country ...