Clean energy now! (E Word).

Earth Day 2000 is shaping up as a major, watershed event. In addition to thousands of smaller celebrations, a huge April 22 rally in Washington, DC will feature musicians and speakers reaching the multitudes from a solar-powered stage. E's coverage in this issue is designed both to highlight the spectacular array of events taking place across the country and the world, and to help empower our readers to act locally. Whether you plant a tree or host a live Internet concert, it all honors the Earth.

That zero-emissions stage is symbolically important for an event whose theme is Clean Energy Now! The Earth Day Network has identified four priorities to lessen our dependence on polluting fossil fuels: clean power, including solar and wind energy; clean air, through tighter federal regulation; clean investments, in renewable energy and energy efficiency; and clean cars, in both hybrid (gas and electric motors) and fuel cell forms.

The fuel cell cars featured in this issue hold out the tantalizing prospect of eliminating the automotive tailpipe, replacing smog-causing emissions with the drip of clean water. But environmentalists may well ask, is that enough? Isn't it cars themselves that are the problem? Cars, with their sheer numbers increasing exponentially, demand more and more of our physical space, for highways, parking lots and garages. Unfortunately, that isn't likely to change anytime soon.

Despite growing awareness of problems such as global warming and a willingness, expressed in many opinion polls, for a fuller range of mass-transit options, Americans are depending on their gas guzzlers more than ever.

Today, just 2.5 percent of American trips are taken in all forms of public transportation put together, including buses, subways, light rail, trains, planes and even taxis. Americans use twice the energy per person of Europeans, who drive half as much and use mass transit as much as 10 times more. So even an incremental improvement in how cars perform makes a huge difference.

Cars, of course, are only part of the problem. As the Earth Day Network points out, half of the electricity in the United States comes from burning coal, and coal-fired power plants escape regulation under the Clean Air Act because of loopholes in the law. Efforts by the Environmental Protection Agency to get tough on profitable coal plants, particularly in the Midwest, have met with howls of protest from industry.

Earth Day's energy agenda is both sensible and achievable, and it starts with closing the coal loophole. By 2020, organizers say, we can produce a third of our energy from renewable sources. Fuel cells, which can provide clean electricity for houses as well as power laptop computers and other devices, will be part of that mix. Cleaner cars will enter into the equation also. Although Americans have become fixated on gas-guzzling sport-utility vehicles, Earth Day proclaims the laudable goal of attaining an average of 45 miles per gallon for cars and trucks by 2010, and 65 miles per gallon by 2020. Since Ford, DaimlerChrysler and General Motors are displaying 80-mile-per-gallon prototypes, that goal is not as outlandish as it seems.

Every day, at every meal, people make important decisions about what they eat based on such factors as taste, price, packaging and health. Unfortunately, one consideration usually gets left out: the planet. With a new column debuting in this issue entitled "Eating Right," E acknowledges critical environmental dimension to our diets.