Millions of historic sites, crumbling and collapsing in national forests around the country, are in danger of being lost forever, according to a study set to be released today by a prominent preservation group.

The National Trust for Historic Preservation estimates that only a small slice of about 2 million "cultural resources" that sit on 193 million acres managed by the U.S. Forest Service have been properly preserved.

Their deterioration has been accelerated by vandalism, theft, fire, damage from off-road vehicles and other recreation, as well as oil and gas extraction, mining, timber harvesting and grazing, the study found.

The resources include Native American archaeological sites, Civil War battlefields, ranger stations, fire lookout towers, cabins and camps built by the Civilian Conservation Corps.

Not exactly on a footing with the Old North Church in terms of historic importance but still worth preservation, said Richard Moe, president of the organization.

"All of these places represent a different part of our heritage," Moe said. "From the first imprint of man on this land, the first Americans, to the old miners' cabins and watchtowers. We're not saying everything needs to be saved. But they all represent a different experience in the country."

The study credited the Forest Service for its attempts to preserve and maintain some of the sites but said it faces an overwhelming task.

The Forest Service, part of the Department of Agriculture, does not know how many sites of archaeological, historic or cultural importance exist on the land it maintains, because a complete audit has never been performed. The agency examined 20 percent of its land and identified about 325,000 "cultural resources" as of last year. Of those, 50,000 were determined to be eligible for listing in the National Register of Historic Places, and a tiny fraction -- 27 -- were awarded National Historic Landmark status.

Achieving landmark status costs time and money, resources in scarce supply at the forest service, the study found. The agency cannot even afford volunteers; in 2004, the Forest Service turned away more than one-third of the people seeking to help agency archaeologists because it did not have the resources to organize them, the study said.

As firefighting consumes an increasing portion of the agency's budget, the amount set aside for heritage programs has decreased. In the current fiscal year, $14 million of the Forest Service's $4.4 billion budget -- 0.3 percent -- is devoted to heritage programs.

Joel Holtrop, deputy chief for the national forest system, shrugged off suggestions that his agency lacks the money for historic preservation. "We have a large, diverse mission and many programs we're responsible for. Heritage resources is one," he said. "We need to make sure all of our resource programs . . . have the ability to compete appropriately for scarce federal dollars."

The National Trust for Historic Preservation wants Congress to nearly double the agency's historic preservation budget, one of 11 recommendations it made to improve the forest service's management of historic properties.

Private organizations are funding more historic preservation on forest service land than the government is, Moe said. In 2006, private groups, including Moe's organization, gave $32 million toward preservation projects on forest service land, more than twice what the federal government spent, he said.

"The primary responsibility has to be with the owner of the property, and that is the federal government," Moe said. "Private partnerships are welcome, but this is about stewardship."

Holtrop thinks otherwise.

"I'm not sure the fact that we've been able to leverage funds should be considered anything other than success," he said. "That's exactly what the American public should have a right to expect of an agency like the forest service. We seek ways to leverage those funds to get as much done with scarce dollars as possible. "

The trust wants the Forest Service to develop a plan to determine the number of historic sites on its land and to set priorities for preservation. It also wants the agency to allow some of the historic buildings to be leased for public use.