Paul Ehrlich Addressing Vatican Conference on Biodiversity.

The population doomsayer's back!

Forty-nine years ago, Professor Paul Ehrlich of Stanford University scared the bejesus out of much of the world when he predicted that overpopulation would lead to mass starvation. In his doomsday bestseller The Population Bomb, Ehrlich wrote, "The battle to feed all of humanity is over. In the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate."

Since Ehrlich wrote those words, the world's population has more than doubled. Yet people consume more calories per capita while living longer on a cleaner planet. Ehrlich's jeremiad did not come true for a number of reasons. The Green Revolution massively increased agricultural productivity, affordable contraceptives made family planning easier, plummeting infant mortality has reduced the need for "spare" children, and rising incomes increased the opportunity cost for women who opt to stay at home with their children rather than enter the labor market—hence massive fall in global fertility rate.

That said, Ehrlich's predictions were not without consequences. "In addition to China's one-child rule," Ehrlich must be held partially responsible for "abhorrent campaigns of forced sterilization in Indira Gandhi's India and Alberto Fujimori's Peru." Surely a man with that much to answer for has been relegated to the fringes of society? Not on your life! In fact, next month Ehrlich will be addressing a Vatican workshop on "Biological Extinction." Judging by the promotional material, he will feel right at home.

According to the Vatican, measures of human consumption have "calculated that in about 1970 we were using about 70 percent of the Earth's sustainable capacity, and now…we are using about 156 percent. Nevertheless there are 800 million people chronically malnourished and 100 million on the verge of starvation at any one time. How have such imbalances, both among contemporaries and between the present and future generations come about, and how are they sustained? The problems wouldn't go away if we had another 56 percent of the Earth to take care of our needs, but we could at least stop eating into the productive capacity of the Earth progressively as the years go by."

Human settlement and agriculture have been the traditional enemy of nature and biodiversity. Thankfully, urbanization (over half of humanity lives in cities already) and falling fertility rates (there is a distinct possibility that earth's human population will start declining during the course of the 21st century) will return some of the world's surface back to nature. This trend will be greatly enhanced by improvements in agricultural yields. As Jesse H. Ausubel of Rockefeller University points out, "if the world farmer reaches the average yield of today's U.S. corn grower during the next 70 years, 10 billion people eating as people now on average do will need only half of today's cropland. The land spared exceeds Amazonia. This will happen if farmers sustain the yearly 2 percent worldwide yield growth of grains achieved since 1960, in other words if social learning continues as usual."

If the Vatican wanted to get a real sense of the future of biodiversity on earth, it should have invited Ausubel instead of Ehrlich.