Yesterday Americans celebrated our 33rd Earth Day. I spent the first fighting to protect the Lincoln Backcountry from the U.S. Forest Service. They proposed an economically idiotic development plan for that high-elevation and extremely fragile area.

In 1972 we won that battle and I've seen great environmental progress since. The air and water are cleaner and people, especially young people, are more environmentally sensitive. While serious problems remain, the easy fruit has been picked. Americans now confront more subtle and contentious environmental issues.

We are, however, well prepared to deal with them. Our science has improved dramatically. We have cause-and-effect models and much better measures of impacts. Further, our understanding of human-environmental relations has advanced. Here are a few certainties.

First, we understand that education and responsible prosperity foster environmental sensitivity. Hungry folks don't have the luxury of investing in the preservation of endangered songbirds. Second, we recognize that command-and-control regulations have serious limitations and are often grossly counterproductive and inefficient. Third, we have witnessed the success of public but nongovernmental organizations ranging from the international Nature Conservancy and Ducks Unlimited to thousands of local groups such as the Gallatin Valley Land Trust. We've come a long way since the first Earth Day.

Ecotopia, however, remains elusive. It always will. That problem is inherent to the nature of things. Here's one reason why. Environmental issues are unique in the following respect: all conjoin technical, scientific complexity with high emotional loading. No other policy arena consistently labors under this twin burden. Rarely are the problems and solutions obvious and easy.

We have successfully confronted significant environmental problems such as lead. But the professional environmental movement has strong incentives to portray environmental threats in apocalyptic terms. At times it employs pseudoscience to achieve its goals. This tactic is counterproductive. It diverts attention and scarce resources from serious problems. The orchestrated scare surrounding Three Mile Island is illustrative.

Last month the respected journal Environmental Health Perspectives published a 20-year follow-up study of over 23,000 people living near the Three Mile Island (TMI) nuclear plant. Researchers looked at causes of death from heart disease and cancers, including those known to be sensitive to radiation effects such as bronchial, breast, blood, and central nervous system cancers. It found no significant increase in cancer deaths among residents.

Both the U.S. Department of Energy and the Pennsylvania Department of Environmental Resources tested hundreds of air samples in the vicinity of TMI shortly after the accident. They discovered only average levels of radioactivity. University of Pittsburgh professor Bernard Cohen asserted that "the average person living near Three Mile Island received as much extra radiation from that accident as he would get from a one-week visit to Denver."

The late astronomer Carl Sagan wrote The Demon-Haunted World: Science as a Candle in the Dark to rouse us from our neglect of science. Sagan wondered why so many people embrace the sort of pseudoscience associated with New Age beliefs. Widespread scientific illiteracy and a dearth of critical thinking are "perilous and foolhardy," and that's obviously true. Stick to the facts, Sagan tells us, "There are wonders enough out there without our inventing any."

Harvard astrophysics professor Sallie Baliunas provides an example. Europe enjoyed a warm climate between the 9th and 12th centuries, the time when the Vikings settled Greenland (when it was actually green). But by the 14th century the Little Ice Age had emerged. "One severe frost in 1626 froze lakes and rivers, decimated crops and wild vegetation...." At the time this was "unnatural." The cause -- witchery. The solution -- burn "witches," 2000 in Cologne, Germany alone.

The environmental movement is far more sophisticated today than in 1970. They are recognizing that "crisis entrepreneurs" and hysterical environmentalism ultimately backfire. Greenpeace International's mission against chlorine is an excellent example. Their anti-chlorine campaign led Peru to reduce the chlorine it added to its water supply. The result? A cholera epidemic swept through insufficiently chlorinated water supplies, taking far more lives than the chlorine ban could possibly have saved.

Sincere and sensible environmentalists shun such chicanery. Instead, they promote policies based on sound science and economics, not the machinations of crisis entrepreneurs. This is a victory to celebrate on Earth Day.