GETTING YOURSELF AND YOUR KIDS INTO the great outdoors may be the most essential step you can take to save the planet. Children (and adults) are increasingly plugged into electronic screens for entertainment. What you may not realize is the compounding impact of this trend: the less often people get out into parks and reserves, the less concerned they are about nature’s fate, and the more the budgets for these lands are cut because of lower attendance.

The iconic American family vacation to a national park, after 50 years of rising popularity, is now in steady decline. From 1987 to 2007, per capita visits to national parks shrank by 23 percent. When I learned of these numbers, alarm bells went off in my head. I am a stream ecologist but also a mother of three young children. What would my generation’s conservation legacy be for them?

I partnered with Oliver Pergams, a fellow parent and conservation geneticist at the University of Illinois at Chicago, to find out. Surprisingly, we discovered that 97.5 percent of the decline in national park visits could be explained by just four factors: the rising price of gasoline and the increasing amount of time people spend plying the Web, playing video games and watching movies. Although correlation is not causation, the relationship was strong. We coined the term “videophilia” to describe “the new human tendency to focus on sedentary activities involving electronic media.” This phenomenon is in contrast to “biophilia,” a recognized term that describes humans’ basic affinity for nature.

To see if we were witnessing a fundamental change, Pergams and I then evaluated 16 different surveys of Americans’ interactions with nature—from obtaining fishing licenses to hiking. We also checked national park visits in Spain and Japan. The results strongly indicate that people in the U.S. and other developed nations are spending less and less time in state parks, national parks and national forests.

Nature lovers might welcome these data, thinking that less invasion means less wear and tear. Yet studies suggest that being a nature advocate is closely related to time spent in nature, particularly as a child. As people experience natural places less and feel less vested in them, the growing pressures for urban development, oil and natural gas drilling, coal mining and logging are likely to take priority. As popular as the green movement may be, when it comes to voting, funding or budget cuts, priorities make the difference. Sure enough, state park closings are on the rise. As Peter Kareiva, director of science at the Nature Conservancy, said about our research: “If people never experience nature and have negligible understanding of the services that nature provides, it is unlikely people will choose a sustainable future.”

We need environmental stewards now more than ever. Yet we are raising a generation of young people whose primary experience with nature is virtual. Real nature is a full sensory experience, with frequent open-ended problem-solving opportunities and no off switch. We should all make outdoor play a priority for our children and ourselves. Nature: use it or lose it.