ARNO CHRISPEELS, A HIGH SCHOOL SCIENCE TEACHER in Poway, California, recently asked his students to list the messages they hear most often about the environment. The students offered a few positive statements about the beauty of nature, but the dominant themes were fear, death, and loss:

"Humans are a bad environment for other humans."

"You will see the earth reach its end."

"The environment will die."

"If you go out [in nature], there has to be a parent because you can't protect yourself." And so on.

Earlier that month, Chrispeels had invited a biology professor from the University of California at San Diego to speak about overpopulation. "He basically told them that we've run out of time. The kids' eyes froze over," Chrispeels says. They'd heard that message before.

In many of the interviews I've been doing with young people in recent years, I hear the same hopelessness. "When I think about the destruction of the environment, it's too painful," a 17-year-old student told me. "So I don't think about it."

In an era when politicians routinely ignore the challenges of climate change and other environmental threats, such a reaction is understandable. Yet if our goal is to save the natural world, despair will not get us there. Moreover, many of the kids we are scaring about nature have had precious few opportunities to directly experience its joys and mysteries. As naturalist Robert Michael Pyle writes, "What is the extinction of a condor to a child who has never seen a wren?"

David Sobel, codirector of the Center for Place-Based Education at the Antioch New England Institute, was one of the first to ring the alarm about this phenomenon. He described the growth of "ecophobia," a debilitating fear for the future of the planet. "Between the end of morning recess and the beginning of lunch," Sobel writes, "schoolchildren will learn that more than 10,000 acres of rainforest will be cut down." Then they'll be told that "by recycling their Weekly Readers and milk cartons, they can help save the planet" and grow up to be responsible stewards of the earth. Or will they?

Children learn about rainforests, writes Sobel in Beyond Ecophobia: Reclaiming the Heart in Nature Education, but usually not about their own region's forests or "even just the meadow outside the classroom door." While young people do need to know about ecological deterioration, Sobel found that emphasizing gloom and doom too early "ends up distancing children from, rather than connecting them with, the natural world. The natural world is being abused, and they just don't want to have to deal with it." Emotionally, they turn off.

Indoctrination in ecophobia begins early; a new genre of well-intentioned but dismal children's books has appeared, so that bedtime readings are often tales of ecological collapse. The next day at play, children are increasingly unlikely to experience the balancing joy and wonder of nature.

Over the past 15 years, I have interviewed families across the country about the changes in their lives, including their relationship to nature. With few exceptions, even in rural areas, parents say the same thing: Most children aren't playing outside anymore, not in the woods or fields or canyons. A fifth-grader in San Diego described his world succinctly: "I like to play indoors better 'cause that's where all the electrical outlets are."

When asked why their kids resist going outside, parents point to diminishing access to natural areas, competition with electronic entertainment, longer school hours, increased homework, and other time pressures. Most frequently, though, they (as well as school officials) cite fear--of traffic, of being sued, and, above all, of strangers. Despite evidence that the number of child abductions has been falling for years (and most of those that do occur are not by strangers), many parents and kids now firmly believe that a bogeyman--if not the Blair Witch--lurks on every street corner and wooded lot.

One antidote to the fear of "stranger danger" is to start thinking in terms of comparative risk. Yes, there are hazards outside the home. But, in most cases, they pale in comparison to those of raising young people under what amounts to protective house arrest. Kids growing up indoors may suffer fewer broken bones and skinned knees, but pediatricians now report an increase in children with repetitive stress injuries, which can last for decades. Too many limits on outdoor play may also put children at risk of diabetes: A third of U.S. children and teens--25 million kids--are either overweight or nearly so. That's the highest number ever recorded, according to the National Health and Nutrition Examination Survey.

By not getting outdoors, science is demonstrating, kids are missing out on the enormously positive impact of direct nature experiences on their cognitive development, creativity, and emotional health. Environmental psychologists report, for example, that greenery in or around the home helps reduce stress and maintain children's mental well-being. A study by researchers at the Human-Environment Research Laboratory at the University of Illinois at Urbana-Champaign revealed that children as young as five show a significant reduction in the symptoms of attention deficit disorder when they engage with nature. Other studies show that kids who play in natural settings are more cooperative and more likely to create their own games than those who play on flat turf or asphalt playgrounds.

Students in schools that use outdoor classrooms also do better academically across the board, from social studies to standardized test scores. A 2005 study conducted by an independent research group, funded by the Sierra Club and released by the California Department of Education, found that kids in outdoor classrooms improved their science scores by 27 percent. Rather than canceling recess and field trips, as many school districts are doing, the evidence suggests that students need more time learning outside the classroom.

Beyond leaving no child behind, we need a "Leave No Child Inside" campaign to reconnect kids with the restorative, challenging, primal qualities of nature. Such a movement is now being born. In the past year, nature-focused preschools and public high schools have been established, and major environmental organizations as well as several state governments are substantially increasing their commitment to getting kids outside.

But getting children out in the woods is not necessarily enough to counteract ecophobia, the dread of losing those woods. Dealing with such hopelessness requires that we reconnect with the optimistic, assertive spirit that fueled earlier environmentalism. That doesn't mean we should hold back on reporting bad news to young people at an appropriate age, but we must dramatically widen the discussion. Bradley Smith, a dean at Western Washington University and former president of the Council of Environmental Deans and Directors, takes issue with the bleak views he hears expressed by students. "During the next 40 years, we're going to have to do everything differently," he says. He doesn't mean that to be depressing news; far from it. From green architecture to organic farming to alternative energy, Smith foresees an array of exciting careers emerging as we build a new, greener civilization. That's the kind of message that will turn despair into creativity and hope--especially when accompanied by more time spent in nature.

As evidence, there's the second stack of student papers Chrispeels sent me. He'd challenged his students to spend a half hour in a natural setting and to write about it. That may not sound like much time, but for some of these youngsters, it was an introduction to a new world. Among 100 essays, there wasn't a cynical or despairing one. Confronted by nature, the teenagers expressed awe and surprise.

"For the past few months, I've found myself unmotivated," wrote one young man. "I almost felt a disconnection from myself because I couldn't take the time to think. When I sat down in nature to write this weekend, I found myself reconnected, my insides and outsides." Another student noticed that "it wasn't boring at all being alone, and I saw more stars than I have probably ever seen in my entire life."

What these young people experienced, if in the smallest of tastes, was something they'll never get from a video game: a sense of the possibilities of the vast, unnoticed universe. It's up to those of us who were lucky enough to grow up in closer contact with nature to help kindle that spark. Just as the light can go out in children's eyes, it can quickly come back on again.