<p>For the first Earth Day in 1970, overpopulation guru Paul Ehrlich wrote a fictitious report for the Progressive presenting an eco-gloomster's portrait of the U.S. in 2000. The population had fallen to 22.6 million, 8% of the current population, and the diet was less than the daily calorific intake of an African. By 1974, Mr. Ehrlich and his wife, Anne, worried that "global cooling" would diminish agricultural output -- that the world was becoming unsustainable.</p>