PHILADELPHIA -- It's windy. Rain is imminent. The path is muddy. But Patricia Zaradic is loving it all.
What's important is that she is out in nature, a place her research tells her fewer and fewer Americans are heading.
In the past two decades, park visits, permits for camping or fishing and other data show a pervasive shift away from outdoor activities, the ecologist concludes in a study published recently in The Proceedings of the National Academy of Sciences.
National parks are still popular; last year, 275 million people visited them. But adjusting for population increases, Zaradic says attendance is 70 million short of a 1987 peak.
Participation in outdoor activities has declined 18 percent to 25 percent, according to the study co-authored by University of Illinois conservation geneticist Oliver R.W. Pergams and Zaradic, a regional fellow with the nonprofit Environmental Leadership Program. They link the decline to a phenomenon they term "videophilia," the tendency to do stuff indoors, in front of a screen - such as watching TV, sitting at the computer or playing Xbox.
The authors say the trend has impact well beyond the nation's expanding waistline: It could blunt conservation efforts and other activities that depend on an appreciation of nature.
And not just experiences at Yellowstone. Even the small realm of bugs and earthworms and fallen leaves in the American backyard has import, Zaradic said. It's something "you just can't get from a flat screen, no matter how high-D it is."
The trend worries leaders of environmental organizations.
Bill Kunze, Pennsylvania director of the Nature Conservancy that funded Zaradic's research, called it "an interesting paradox" that people are participating less in nature activities as interest in the environment is growing, prompted by concerns over global warming: "I don't think they've made the full connection between climate change and nature."
Pergams and Zaradic began studying how people relate to the natural world several years ago. In their current paper, amid all the downhill data, they found one tiny increase: People went from hiking once every 12.5 years to once every 10 years.
A recent 15-year trend analysis by the U.S. Fish and Wildlife Service echoes their findings. It shows declines of 16 percent among anglers, 11 percent among hunters and 23 percent among those taking trips to watch wildlife.
National Park Service spokesman Gerry Gaumer acknowledges that park officials don't see "as much of the family vacations as we used to," although "I don't see that there's any crisis as to visitation."
Some say video games and TV aren't the only problems. Homework has increased. Ditto scheduled activities.
Richard Louv, author of the book, Last Child in the Woods: Saving Our Children From Nature-Deficit Disorder, said a major issues is access: "It's pretty tough to go out in the woods if it's been cut down."
Sandy Bauers writes for the Philadelphia Inquirer.