In the years after World War II, Americans packed up their young families and Army surplus camping gear and headed into the national forests to hunt, fish, and hike. Going to the woods was part of what it meant to be an American.

Today, however, visits to the national forests are off 13 percent.

Top officials at the U.S. Forest Service blame it on circumstances outside their control — rising gas prices, the popularity of video games and the Internet, and an increasingly urban and aging population less inclined to camp out.

Critics focus on fees charged for hiking trails and visitor centers, a proliferation of noisy off-road vehicles and the declining proportion of the Forest Service budget dedicated to recreation.

James Johnston, a policy analyst with Forest Service Employees for Environmental Ethics in Eugene, spent the last year camping out in 67 national forests and talking to 400 people. He concluded that while fewer people may be using the woods, fewer trails and campgrounds are open and there are more people riding noisy off-road vehicles.

"They think that it's harder to find solitude," he said of the people he talked to.

Coupled with the decline in visits to national parks, the trend makes nature lovers nervous at a time when the growing global population and climate change pose huge threats to wild places.

"We only value what we know and what we love," said Richard Louv, author of "The Last Child in the Woods." "Where is the political constituency going to come from if all those trends continue — disinvestment in facilities, lack of diversity, the disconnect between children and nature?"

If young people and the growing Hispanic population don't fill in for the aging white Baby Boomers who have long made up the vast majority of national forest visitors, what will that mean for the future?

"That is the big question," said Thomas More, a research forester with the U.S. Forest Service Northern Research Station in Burlington, Vt. "Is it going to be a future of hiking or is it fancy cafes and city kinds of things? That's what we're trying to evaluate right now. And the information is mixed, frankly."

The national forests date to 1891, when Congress authorized reserves to protect forests from cut-and-run logging. The system has grown to 155 national forests covering 190 million acres.

Though they were always used for recreation, there was no legal recognition of that role until the Multiple Use Act of 1960, said James G. Lewis, historian for the Forest History Society in Durham, N.C.

The Forest Service didn't conduct a statistically rigorous survey of visitation until 2000. That National Visitor Use Monitoring program found 204.8 million visitors annually in the period 2000-2003 and 178.6 million for 2003-2007 — a decline of 13 percent. When compared to the rising population, the proportion of Americans visiting national forests is falling even faster.

More said the decline appears to have started in the 1980s, during the Reagan administration, when the Forest Service became much more interested in logging than recreation.

"Remember Reagan's famous quote about if you've seen one redwood you've seen them all?" More said.

The Endangered Species Act slowed logging in the 1990s, demanding more habitat for the northern spotted owl and other wildlife. Without the revenue from timber, the Forest Service got Congress in 1996 to allow fees for trails and other amenities.

Scott Silver, executive director of Wild Wilderness in Bend, sees a strong correlation between the imposition of fees and declining visits.

"They raised the fees, and people stopped coming," Silver said. "The theory of supply and demand, price and elasticity was proven. Now that they've seen demand drop, they're saying `Oh my goodness, we've got to figure out how to increase visitation."'

Top Forest Service officials reject Silver's assertion about fees. Although their surveys don't address the question, they attribute the decline primarily to the older and more urbanized population, and increasing popularity of electronic entertainment and to rising gas prices.

"For families of modest means with large vehicles who have got to travel large distances, even the prices of two and three years ago were starting to cut into the recreation opportunity," said Mark Rey, undersecretary of agriculture in charge of the Forest Service.

"We are seeing less participation in overnight camping than the quick day trips," said Forest Service recreation director Jim Bedwell.