We have 40 years in which to shape up. If we fail, "environmental deterioration and economic decline will be feeding on each other, causing social structures to disintegrate." Doom-filled scenarios are as pervasive as urban smog these days, but when they come from Lester Brown, environmentalists take special notice. Brown, 56, is president of the Washington, D.C.-based Worldwatch Institute, which recently published its seventh annual State of the World, a highly regarded report on the planet's failing health. This year's, the grimmest yet, has inspired Race to Save the Planet, a 10-week series that will air on public TV starting in October.

Brown began thinking about the relationship between man and his environment as the son of a small farmer in Bridgeton, N. J. Soon after graduating from Rutgers University with a degree in agricultural science, he joined the U.S. Department of Agriculture. Fifteen years later, with the help of the Rockefeller Brothers Fund, he founded Worldwatch. Today the divorced father of two grown children goes food shopping with a canvas bag and walks the 10 blocks between his one-bedroom Washington apartment and his office. He talked with correspondent Margie Bonnett Sellinger about the critical condition of the Earth and what we must do to bring it back to health.

This spring an estimated 200 million people celebrated Earth Day. Will the event make any difference?

When the sun rose in Japan and started moving westward around the world, people in country after country—140 all told—were involved. There's never been an issue that has mobilized so many people. There's no question that Earth Day is going to affect people's thinking because of the vast media coverage the issues got. A lot of people got the equivalent of a three-credit course in environmental science. It has to make a difference. People have to understand the need for a change before they will support change. Every year the environmental degradation of the planet continues. People won't accept it indefinitely.

What do we do to start reversing these trends?

It's going to take a lot of education to help people understand that if we don't create an environmentally sustainable economic system, there's no future. One of the problems at the moment is that we don't have effective leadership. President Bush claims to be an environmentalist, but he has opposed U.S. support for two principal family-planning assistance agencies, the United Nations Population Fund and the International Planned Parenthood Federation. He's talked about heading off global warming, but he's hardly done anything. We've become part of the problem rather than part of the solution.

Some people say that too much environmental control would hurt economic growth. How do you answer that?

Economic indicators are flawed in a fundamental way: They don't distinguish between resource uses that sustain progress and those that undermine it. The Gross National Product [the market value of all goods and services produced in a year] undervalues qualities like durability and environmental protection, while it overvalues planned obsolescence and waste. For example, if the oil spilled by the Exxon Valdez had reached a refinery and been processed, it would have modestly boosted the GNP. But spilling the oil generated far more economic activity in cleanup costs. According to a recent report, the Alaska Department of Labor says that the number of jobs statewide is rising. The March unemployment rate of 7.9 percent is the lowest for that month since 1976, when construction of the trans-Alaska pipeline was at its peak. Our economic system measures the cleanup activity as a big increase rather than the environmental loss that it is. So according to our system of accounts, you can boost the GNP by wrecking oil tankers.

The 1990 State of the World highlights soil erosion, climate changes, toxic waste and uncontrolled population growth as among the most serious threats to the world environment. How do we attack those problems?

We need to shift military expenditures into things like family planning, tree planting, energy efficiency and soil conservation. We should use the resources that now go into defense for environmental reconstruction. For example, armies in Africa might be mobilized to plant trees and reclaim the desert rather than engage in military maneuvers.

What will be the long-term results if we fail to protect natural resources?

Both Africa and Latin America ended the 1980s with lower living standards and food consumption than they had at the beginning of the decade. Social disintegration and political instability often follow. Take northern Ethiopia, for instance. Soil erosion has reached the point where there's not enough topsoil to support even subsistence-level farming. People have become environmental refugees. Water shortages will be another problem. If Ethiopia, which frequently suffers from drought, decides to develop irrigation from the headwaters of the Nile, it will be at the expense of Egypt. In years to come, water may replace religion and nationality as a principal source of conflict in this part of the world.

What will our lives be like if we make the necessary changes?

First of all, the "throwaway society" will become obsolete. We will live by what environmentalists call the three Rs of the future: Reduce, Reuse and Recycle. We will see a reduction in food packaging. The package within a package within a package will be a museum piece.

We may not even have fashions. Annual changes of fashion are part of the idea of planned obsolescence that underpins a throwaway society. We'll develop simpler, more durable, more comfortable clothes.

What else will change?

Transportation. New high-speed rail systems may well replace planes and cars as the preferred means of transportation for distances of up to 1,000 miles. Suburbs will be in trouble because they're so automobile dependent. So inner cities could become more attractive as places to live. As electronic technologies continue to advance, fewer people will commute; they'll work out of their homes. And the bicycle will emerge as an important means of short-distance transportation. It's responsive to so many of our problems—air pollution, acid rain, global warming, the need for exercise.

Do you really think Americans will give up their cars?

I'm not convinced that our automobile-centered society represents the ultimate in human social evolution. The frustration, pollution and death toll from cars are really quite high. In the U.S. more than 45,000 people die in motor vehicle accidents each year, and hundreds of thousands more are seriously injured. One indication of how ludicrous our system has become is that thousands of people will get in a car and drive to a health club so they can sit on a stationary bike for half an hour and workout.

How will industry be affected?

There will not be many coal miners, autoworkers or road construction crews in the year 2030. The boom industries will be energy auditing, solar cell manufacture, solar architecture and wind prospecting. In mountain passes in northern California, wind farmers are already selling $12,000 worth of electricity per acre per year. A wheat farmer typically produces $150 per acre of wheat per year.

You give us 40 years. Why?

Globally, our food production systems have evolved during a period of climatic stability over the past 10,000 years. But if we do things to destabilize the climate, as we are doing now, and set in motion a warming process that raises temperatures several degrees over the next half century, we're in trouble. As a result of intense heat and drought in 1988, the U.S. did not produce enough grain to satisfy our own needs for the first time since records have been kept. Fortunately we had a large reserve. There are already parts of Africa where soil erosion is leading to widespread hunger. We can begin to see how global warming could lead to a food emergency, economic crisis and political instability. The changes have to be started during the 1990s—and completed by 2030.