Paul R. Ehrlich could never be called an optimist, but his pessimism has lifted a little. Twelve years ago, Stanford University's renowned population biologist and author of a 1968 best seller, "The Populatin Bomb," was solemnly warning: Curb population and stop destroying natural resources -- or the planet is doomed. Today, he finds the problems just as severe, but the solutions more likely.

A few weeks ago on Stanford's Jasper Ridge Biological PReserve, where Dr. Ehrlich is continuing his famous 21-year study of the checkerspot butterfly, he paused to discuss his cautious new optimism.

"There's good reason to be optimistic," Professor Ehrlich says. "In 1965, when I talked about the chance of controlling the US population, I said we would be lucky to get to a net reproductive rate of 1 by the year 1992. Sociologists told me it would take 20 to 30 years of hard work to get the nation's average family size down from three to tow [children].

"It turned out we were dead wrong. Society was ready for it and it took about three years. In the last 15 years, the environment has become a major political issue. Society can change its ways very fast when it sees reason to. But if you extrapolate today's behavior with no change into the future, we're doomed. The hope is that our behavior will change.

"Eight years ago the Brazilian point of view was, 'You and the rich countries have screwed up your environment for fun and profit. Now it's our turn,' and they launched themselves on the destruction of the Amazon Basin. now there's been almost a complete turnaround. The attitudinal change is there almost globally."

At the root of the environmental problem, according to Ehrlich, is that most Americans -- especially the economists and politicians -- still believe that if air and water pollution is stopped, their problems would be over.

Not so, Ehrlich says. What's missing is any understanding of what he calls the "free public services" provided to human beings by an intricate, but often delicate, network of ecological systems.

"It doesn't take much to change the entire system," the biologist explains. "It's just like a pistol with a six-ounce pull on the trigger. The last 1/100th of an ounce may tip the balance and the gun fires. People now calculate that a singledegree change in the global temperature, put there by carbon dioxide from fossil fuels, could entrain weather change which would devastate agriculture and lead to famines that could kill a billion or more people."

"You've got to remember," he says, "that the ecological machinery is composed of tiny individual species that we are pushing one after another to extinction, without the slightest understanding of the role they play in maintaining us. People are generally agreed that it's not appropriate to whip your horse to death or torture your dog. The question is, how far are they willing to extend that right to other organisms.

"Claude Levi-Strauss, the great French anthropologist, once said -- and he's quite correct -- that the lowliest species of bug is a marvel of magnitude more fantastic than something like the Mona Liza, as far as beauty, intimacy, and irreplaceability."

Americans who consider the idea of ecological disaster rather remote should consult the history books, Ehrlich says. The world is littered with the remains of civilizations unable to maintain their ecological equilibrium.

"The Romans went under, in part, because they destroyed the forests and screwed up their agriculture. In the Tigris and Euphrates Valleys, there's the remainder of a civilization that failed to manage its irrigation. In Cambodia is the remains of a Khmer civilization that has lost the game of tropical agriculture," says Ehrlich.

Americans' false sense of security is largely attributable to a "super science view of the world" -- however serious our problem, they believe technology will find a way out. But according to Professor Ehrlich, the world can no longer bulldoze its way to a solution, partly because science and technology -- the popular panaceas -- are part of the problem.

"If you asked me right now, "Has science been a net benefit or a net harm to mankind? I would have to say, 'I don't know.' So far it's done about as much ahrm as it's done good. Maybe a little more harm than good. Americans are part of the lucky group, but most people in the world are living considerably more miserable lives than they lived six or seven thousand years ago. We are the most vulnerable population the world has ever seen. We're more crowded. We have more undernourished people than have ever lived before," he says.

"The more we learn about ancient hunter and gatherer civilizations, the more it's clear that they led more pleasant lives than the avrage person on the planet today. So agriculture may have been a mistake, and science, which followed after it like the night, the day, may have been a mistake, too. And if we have a nuclear war, there will be no question about it."

Often mankind has to be driven to "the edge" before human behavior can be changed. The problems is that the "edge is getting steeper," the biologist says. Referring specifically to America's tendency to put "all our eggs in the nuclear [energy and defense] basket," he laments: "Sooner or later either a large city will disappear under a terrorist bomb, or there'll be a nuclear war, or a fullscale meltdown, at which point everybody will say, 'OK, no more nuclear power.' But if you've got to be taught a lesson with a war that wipes out 99 percent of humanity and leaves a few scattered groups in the Southern Hemisphere barely struggling on the edge of existence, that's a high price to pay for learning."

Ecologist, he adds, have been warning for years that unless the United states changes its gluttonous ways, it will find itself on the brink of war over scarce world resources. the present crisis in Iran and Afghanistan is precisely that nightmare, according to the professor. He believes Zbigniew Brzezinski, President Carter's national-security adviser, would risk getting into a war that could "possibly end the world, in order to gain access to the last 20 or 30 years of Arab oil. The people who run the country think it's worth going to war over, rather than driving smaller cars."

Next to the possibility of war, the danger that concerns Dr. Ehrlich most is economic growth.

"Economists think that the whole world is just a market system, and that free goods are infinitely supplied. They are a discipline built on transparent mistakes, from the point of view of a physicist or a biologist.

"Economists are probably the most dan they are listened to. They continue to whisper in the ears of politicians, all kinds of nonsense. Everybody feels that the economic system is what dominates human affairs, when actually the economic system is hopelessly embedded in the physical and environmental systems. Economists say it's jobs or the environment, when actually if you don't treat the environment right, there will be no jobs."

Ehrlich's one-word explanation for the United States' "environmental myopia" is "politics." Politicians, he says, have difficulty seeing beyond the next election. "As Churchill or somebody once stated, democracy is a stinking, inefficient system; it just happens to be the best we've got."

While the biologist has no desire for a benevolent dictator, he believes the US needs leaders with backbone to pull it out of the present environmental nose dive.

"In some countries," says Ehrlich, "the government can say, 'If you can't build a car that gets 50 miles to the gallon you won't be allowed to build any.' Instantly you have 50-mile-a-gallon car. I can recall very clearly when we went into the Second World War we tooled up for that in a matter of a year or so. We changed the entire economy. Everybody behaved and pitched in. If you skipped the war itself, the experience was completely untraumatic.

"The sorts of environmental measures that need to be taken today will not be popular because relatively few people understand the urgency of the situation. When people begin to sense the urgency, almost anything goes. That's where my hope lies."

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