FRIDAy, Feb. 8 (HealthDay News) -- National parks were designed to be places where Americans could go to connect with nature, but that healthy ideal may be on the wane.

A new study published in this week's issue of the Proceedings of the National Academies of Sciences finds the use of America's parks and forests may be down by as much as 25 percent since 1987.

"Outdoor health activities in nature are good for you in terms of physical, emotional and psychological well-being," said study co-author Oliver Pergams, a research assistant professor in biology at the University of Illinois at Chicago. "If they're being replaced by videos and other indoor sedentary activities, then kids aren't getting the good stuff. They're replacing those healthy activities with ones that are quite the opposite in many ways."

His team believes the decline in national park use stems from this "videophilia," which they define as the new human tendency to choose sedentary activities involving electronics over outdoor-based recreation.

"National parks and being outside are symbolic of a healthier lifestyle than where America seems to be going these days," added Dr. Marc Siegel, an associate professor of medicine at the New York University School of Medicine. "We've been oriented toward environmental control and want everything to be 70 degrees, so we're not communing with nature as much."

While the United States is clearly a sedentary society, said Siegel, he's not sure that there's a direct correlation between the declining use of U.S. national parks and a sedentary lifestyle.

"It's an interesting fact, but it could just mean that our tastes have changed," said Siegel.

The study authors are particularly concerned that the declining use of national parks might lead to a society that's less concerned with conservation.

"Environmentally responsible behavior results from direct contact with the environment," they wrote. "People must be exposed to natural areas as children if they are to care about them as adults. Extended periods spent in natural areas, as well as creating role models, seem to create the most environmentally responsible behavior."

To evaluate the exact usage of the large parks, the researchers looked for decline in usage for 16 different time periods. They looked at national parks in the United States, Japan and Spain, as well as the number of gaming licenses issued and other indicators of camping, backpacking and hiking.

In the United States, visits to national parks steadily increased from the 1930s until 1987. Since that time, the study found the use of these parks has been declining by a little more than 1 percent each year. For some parks, that's translated to a decline in 25 percent in visits since the 1980s.

The researchers also found that parks in Japan and Spain have experienced a similar decrease in usage.

"The trend in declining nature extends beyond U.S. political and cultural boundaries," they wrote.

The only activity that seemed to increase was day hiking. Other activities studied, such as camping, fishing and hunting, declined during the study period.

That's a shame because "there have been a lot of studies that show that being out in nature and participating in outdoor activities is good for you," said study co-author Patty Zaradic, Environmental Leadership Fellow and conservation ecologist at Bryn Mawr College, in Pennsylvania.

However, based on the new findings, "there would need to be more than 70 million national park visits to get it back up to its peak," she noted.

The good news, however, according to Siegel, is that there probably aren't any dire health messages contained in this particular study. While people participating in fewer outdoor activities may get less sunshine, and therefore less vitamin D, Siegel said that you generally get enough sun exposure to make sufficient vitamin D just from walking to the office from your car.

And, while America is "clearly a sedentary society," he doesn't believe an extra visit or two to a national park will cure America's obesity problem.

But Zaradic believes the problem runs deeper than that. "We tend to underestimate how important it is for ourselves and for our kids to get out and play in the dirt and to vacation somewhere like a state park or national park," she said. "We have forgotten how important our relationship with the real world is for our well-being."

More information

If you want to buck the trend and head outdoors, visit the National Park Service.

SOURCES: Patty Zaradic, Ph.D., Environmental Leadership Fellow and conservation ecologist, Bryn Mawr College, Bryn Mawr, Pa.; Oliver Pergams, Ph.D., research assistant professor, Department of Biological Sciences, University of Illinois at Chicago; Marc Siegel, M.D., internist and associate professor, medicine, New York University School of Medicine and Medical Center, and author, False Alarm: The Truth About the Epidemic of Fear; Feb. 4-8, 2008, Proceedings of the National Academies of Sciences

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