The U.S. Forest Service's "roads to nowhere" actually lead to the loss of billions of taxpayers' dollars and the destruction of irreplaceable natural resources, two environmental groups have charged.

The Wilderness Society and the National Wildlife Federation have joined forces to ask that Congress call a temporary halt to the Forest Service's widespread construction of roads that make government timberland accessible to loggers.

"We have for the last three years told Congress it should put a moratorium on road construction, at least for one year, to get a handle on this thing," said Wildlife Federation lawyer Tom France. "They are building thousands of roads to nowhere."

What particularly galls agency critics is that, in a time of budgetary constraints, it often costs more to build the roads and make other logging preparations than the Forest Service gets from the timber harvests. In other words, the more roads the agency builds, the more money it loses.

A recent Wilderness Society report estimates that the Forest Service's expanding timber program will mean losses of more than $2 billion over the next 10 years. The society's lawyer, Peter Kirby, told our reporter Lisa Sylvester that the figure is based on the World Resources Institute's finding that 75 national forests consistently lose money on their timber sales. Yet the Forest Service plans to expand logging operations in 61 of these forests.

Kirby pointed out that the National Forest Management Act of 1976 ordered the Forest Service to identify lands that are uneconomic for logging and remove them from the timber base. Instead, he said, timber sales in those areas have actually increased.

"Under continuation of current policy . . . annual taxpayer losses on the Forest Service timber program would average at least $190 million per year in the first decade of the {new} plans," the Wilderness Society report says. "This amount climbs to $270 million per year in the fifth decade. Cumulative taxpayer losses in the first decade alone would exceed $2 billion."

The Forest Service disagrees with the society's figures. "Based on our cash-flow analysis, the average annual negative cash flow from 1979 to 1983 was $24.5 million per annum, or about $246 million for 10 years," said Larry Henson, associate deputy chief of the National Forest System. The agency is trying to bring that loss figure down by "productivity improvements," he said.

"The Wilderness Society doesn't count all the benefits," Henson said. "True, most roads are built for timber harvests, but only 8 to 10 percent of the {roads'} lifetime is for logging."

Henson said the roads also are used for access to allow fire protection and insect control, berry picking, hunting, camping, fishing and school buses.

Wildlife Federation official Dave Alberswerth noted that the Forest Service now has 343,000 miles of roads, more than a mile of road for each square mile of forest. And with an overall agency budget of about $1 billion a year, he said, road construction eats up $300 million to $500 million.