As people spend more time communing with their televisions and computers, researchers say it's also resulting in less contact with nature and less interest in conservation and parks.

Camping, fishing and per capita visits to parks are all declining in a shift away from nature-based recreation, American researchers report in the latest online edition of Proceedings of the National Academy of Sciences.

"Declining nature participation has crucial implications for current conservation efforts," wrote co-authors Oliver R. W. Pergams and Patricia A. Zaradic.

"We think it probable than any major decline in the value placed on natural areas and experiences will greatly reduce the value people place on biodiversity conservation."

Children in particular are spending more times away from the great outdoors to focus on things like video games, they said.

"The replacement of vigorous outdoor activities by sedentary, indoor videophilia has far-reaching consequences for physical and mental health, especially in children," Pergams said in a statement.

"Videophilia has been shown to be a cause of obesity, lack of socialization, attention disorders and poor academic performance."

By studying visits to national and state parks, and the issuance of hunting and fishing licences, the researchers documented declines of between 18 per cent and 25 per cent in various types of outdoor recreation in recent years.

The decline, found in both the United States and Japan, appears to have begun in the 1980s and 1990s, the period of rapid growth of video games, they said.

Park visits up in Canada, down in U.S., Japan

Canada's national parks had about 13 million visitors in 2006-07, a slight rise from the previous year and the third straight year attendance rose since 2003-04, when just under 12 million visitors used the areas.

This decade has seen a general decline, however: in 1999-00, Parks Canada said the country's national parks had 16.3 million visitors.

In the U.S., fishing peaked in 1981 and had declined 25 per cent by 2005, the researchers found. Visits to national parks peaked in 1987 and dropped 23 per cent by 2006, while hiking on the Appalachian Trial peaked in 2000 and was down 18 per cent by 2005.

Japan suffered similar declines, the researchers found, as visits to national parks there dropped by 18 per cent between 1991 and 2005.

Backpacking, daytrips see resurgence

There was a small growth in backpacking, but that may reflect day trips by some people who previously were campers, wrote Pergams and Zaradic.

Pergams is a visiting research assistant professor of biological sciences at the University of Illinois at Chicago, while Zaradic is a fellow with the Environmental Leadership Program, Delaware Valley, in Bryn Mawr, Pa.

While fishing declined, hunting held onto most of its market, they found.

"This may be related to various overfishing and pollution issues decreasing access to fish populations, contrasted with exploding deer populations," they said.

The research was funded by The Nature Conservancy.