The designer plague.

• Author: Benford, Gregory

If humanity is a cancer, what is the cure?

In January 1993 I went on a cross-country hike in Orange County, California, to protest a highway soon to go in. Puffing up a hill, I struck up a conversation with a member of the eco-warrior group Earth First!, who wore the signature red shirt with a clenched fist. We mounted a ridge and saw the gray sweep of concrete that lapped against the hills below.

"Looks like a sea of shit," the Earth Firster said. "Or a disease."

That same month the National Academy of Sciences and Britain's Royal Society jointly warned of the dangerous links between population and environmental damage. Following this up, the Union of Concerned Scientists mustered 1,500 experts to sign a "World Scientists' Warning to Humanity" and published it in leading newspapers. Heavy hitters, these, including the predictable (Linus Pauling, Paul Ehrlich, Carl Sagan), the inexpert but sanctified (Desmond Tutu), but also the heads of many scientific societies, Nobel laureates, and authorities in many fields. One such laureate, Henry Kendall of MIT, is leading the New Cassandras in a campaign to rouse the intelligentsia.

He makes his case thus: World population grows by 900,000 yearly and will double within half a century, maybe less. Meanwhile, the Green Revolution is apparently over; world crop production per person has declined. About 10 percent of the earth's agricultural land area has been damaged by humans. Half of all nations now have water shortages.

But such policy-wonk numbers, the ecologists remind us, are too human-centered. Our swelling numbers have their greatest impact on defenseless species in rain forests, savannahs, and coral reefs. Biologist E.O. Wilson of Harvard warns that we could lose 30 percent of all species within half a century, and that might be only the beginning.

Humans exert selective pressures on the biological world. North Atlantic waters show a pattern of overfishing, and ever-shrewd nature has filled these niches with such "trash fish" as skates and spiny dogfish that we cannot eat and thus do not take out. Monoculture farming worldwide gains efficiency by growing the same staple--wheat, rice, corn, trees--over a large area, but this is inherently more fragile. Diseases and predators prey easily, and already erosion is a serious threat in many such areas.

Still, hand-wringing is not new, and skepticism about it is well earned. Paul Ehrlich's alarmist The Population Bomb has yet to explode, 25 years alter publication. And there are counter-trends. The "developing world"--to use the latest evasive tag attempting to cover societies as diverse as Singapore and Somalia--is the great engine of population growth, but its pattern is not an exponential runaway.

It may, in fact, follow that of the industrial world, whose net growth curve broadly peaked around 1900 at a rate of 1 percent a year and is now a fourth of that. The poor countries may have entered just such a transition era. Some nations began peaking in the 1970s, and others are joining them. Still, the plateau average rate is 2.5 percent a year, so they have a long way to fall.

Environmentalists and professors alike fear their growth rates won't decline, at least not soon enough. This is where the Earth Firsters merge with the academics--in a profoundly pessimistic view of our collective, shared from the hushed halls of Harvard to the jerky hip-hop images of MTV.

Robert Malthus, the original population prophet, thought that civilization would hit the wall in the late 19th century. Despite failures, such predictions still work as propaganda. The wealthiest man in America, Warren Buffett, devotes considerable charitable giving to population control, as do several other members of the Forbes 400 wealthiest list. They are alarmed.

I suspect there is more here than a Malthusian malaise. While there are ever more mouths, there is also possible global damage unimagined by Malthus, a far more muscular feedback effect. These could tilt the entire biosphere against many species, including us.

A biologist recently remarked to me, "We've just run out of new niches. So the whole system will do a little feedback stabilizing." The vast, numbing menu of looming potential disasters--lessening fish stocks, water, topsoil; dwindling rain...