LESTER BROWN has a vision for how a globally sustainable society would look in the future:* Aerodynamic fuel-efficient four-passenger cars would get between 70 and 90 miles per gallon. * Homes would be weather-tight and highly insulated, reducing the need for heating and cooling. * Waste-reduction and recycling industries would replace garbage collection and disposal companies. * Appliances such as refrigerators, air conditioners, and clothes driers would be more than three times as efficient as those used today. * Telecommunications would substitute for business travel and shopping, cutting air pollution and fuel consumption. The technology to create such a world is available now, says Mr. Brown, founder of the Worldwatch Institute, a Washington, D.C.-based research organization concerned with environmental and economic issues. Countries must take giant steps toward adopting such approaches by the end of this decade or "we'll be in deep trouble," Brown forecasts. Brown and two other Worldwatch Institute researchers outline a blueprint for a globally sustainable society in "Saving the Planet" (W. W. Norton, $19.95, cloth; $8.95, paper) - the first in a new book series. Unlike the Worldwatch Institute's annual State of the World reports, which detail escalating environmental and economic problems, this book sketches ways to achieve environmental sustainability. It reviews how energy systems, tax systems, industrial and developing economies, and international aid wo uld be restructured. "We thought it important ... particularly with the Brazil conference coming up next year," Brown said in a recent Monitor interview. In June 1992, environmentalists, activists, and representatives from nearly every country will meet in Rio de Janeiro for the United Nations Conference on Environment and Development. Participants in what is being called the "Earth Summit" will discuss ways to reverse alarming trends in world hunger, environmental degradation, and overpopulation. Brown says sustainability is a term that many people use but do not understand. He defines a sustainable society as one that satisfies the needs of the current generation without jeopardizing prospects for future generations. Right now "we are on a self-destructive course," he says. Destruction of plant and animal species, deforestation, air and water pollution, overpopulation, and world poverty threaten the planet's ecosystem Stabilizing world population and improving the climate are two problems that should be dealt with first, Brown says. "One requires a revolution in reproductive behavior; the other requires the restructuring of the world energy economy." Convincing industries, individuals, and industrial and developing world leaders to steer in this direction is the hard part. "I have a feeling that policy is going to be driven substantially by events in years ahead," Brown says. "The interesting question is, 'What might be the Pearl Harbor in the battle to save the planet?' It could be a severe heat and drought in the central North American continent that would lead to a crop failure ... or new evidence of health problems from ozone depletion." Some nations are leading the way in moving toward sustainable practices. Brown cites the Netherlands, Norway, Sweden, and Germany as countries that are taking innovative steps to reduce pollution, and reuse and recycle goods. Other success stories exist. The United States has reduced soil erosion by one-third since 1985 and will likely reduce it another one-third by 1995, Brown says. California is pioneering the way in its use of alternatives to fossil-fuel energy. What does he think will result from the "Earth Summit"? Brown pauses. "A lot of frustration," he says.