WASHINGTON - Each dollar spent on a national park generates at least $4 of value, but despite that clear economic payoff the parks suffer from underfunding, a new study says.

The report cited the greater Yellowstone area and Flathead County, Mont., near Glacier National Park as two areas where economic growth has been particularly strong because of the parks.

In releasing the report, the regional office of the National Parks Conservation Association and the Travel Industry Association of Montana jointly called for significant new funding for the parks in the 2008 budget.

"Our national parks are exceptional economic generators, but need our careful care and attention," Homer Staves, president of the travel association, said in a statement.

"If we continue to shortchange the parks of needed funding, we are shortchanging educational programming, maintenance and the preservation of the very resources that lure visitors," he added. "Ultimately we are shortchanging … businesses and communities."

Sen. Craig Thomas, R-Wyo., who heads the key national parks subcommittee, said he "wholeheartedly" agrees that parks funding is an economic benefit to gateway communities.

"That's one reason that I've requested additional funding for our national parks each of the last six years," he said in a statement. "For this coming year we requested significant additional funding for our parks heading into the centennial in addition to an increase to the park operations budget of $150 million."

Thomas wrote a letter signed by 31 other senators to appropriators requesting that increase.

The greater Yellowstone area surrounding Yellowstone and Grand Teton parks has shown remarkable economic growth, the report said. It cited earlier studies showing that the area's population grew by 61 percent over the last 30 years, compared with 38 percent nationally.

"In large part, the establishment of new small companies has driven economic growth since 1990, some of which include high-wage professional services (economic, finance, legal, insurance, real estate)," the report said.

Personal income growth in the greater Yellowstone area has outpaced state averages for Montana, Wyoming and Idaho, according to the report.

Extrapolating from existing studies on the average value of a park visit, the report said the overall economic benefit of recreational park visitation in the nation in 2004 was $10.1 billion. It emphasized that the figure was a conservative estimate.

Federal appropriations in 2004, 2005 and 2006 were $2.3 billion, which along with revenues of $300 million made for an overall budget of $2.6 billion, the report said.

That means the park system generated at least $4 in value to the public for every tax dollar invested in its annual budget, the report said. But the parks suffer an operating shortfall of $800 million every year, in addition to a "massive multibillion-dollar maintenance backlog," it said.

"As a result, the fiscal crisis confronting the national parks continues to deepen and important park functions go without, park infrastructure decays, natural ecosystems are overrun with exotic species, historical treasures are inadequately preserved, and public safety is jeopardized," the report said.

National parks support $13.3 billion of local private-sector economic activity and 267,000 private-sector jobs, the report said. The parks also attract business and people to the local area, resulting in economic growth over the past three decades that is an average of 1 percent a year greater than statewide rates, it said.

The consulting firm Hardner & Gullison Associates prepared the study for the National Parks Conservation Association.

The researchers reviewed studies of the park system and interviewed 30 experts for the report. They also conducted 12 case studies on specific parks.

The Park Service did an analysis last spring of all 390 parks and came up with similar figures, said David Barna, Park Service chief of public affairs.

About $11.9 billion enters gateway economies as a direct result of a park's presence and operations, including visitor spending and Park Service spending on payroll, that study found.

"The taxpayers are investing about $2 billion in the park system and get about a $12 billion return on that benefit," Barna said.

The new report said the Park Service needs $800 million a year more in order to achieve a "basic level of management," based on Park Service business plans.

Asked about that shortfall, Barna said the Park Service has not talked in such specific numbers.

"Certainly times are tight; they're tight for all federal agencies not involved in the war," Barna said. "Our budget has been tight for the past couple years."

He said the Park Service has seen an inflationary increase in its operations budget each year and has gotten more money from the federal highway budget.

"We think we continue to provide a good level of service and the parks are in pretty good shape," he said. "We're doing the best we can, and we're optimistic about the future."