WASHINGTON -- Thousands of square miles of open land in Nevada provide off-road enthusiasts with ample opportunity to ride freely through the desert.

"You drive down a street in Las Vegas and I guarantee there is some type of OHV parked in every garage," said Don Wall, who races off-road vehicles professionally and uses the acronym for off-highway vehicle.

But some lawmakers, federal bureaucrats and environmentalists are worried about the effect desert and forest riders are having on public land across the West.

Use of off-road vehicles has increased by four times in the last decade, and funding cuts have diminished the ability to take action against rowdy riders, officials said Thursday at a congressional hearing.

"Although OHV use on federal lands is legal on designated roads and trails, it has increased so dramatically that federal managers seem unable to keep up," Chairman Raul Grijalva, D-Ariz., said at a hearing of the House subcommittee on parks, forests and public lands.

Off-road riders make 11.5 million visits to national forests each year, said Joel Holtrop, the deputy chief of the National Forest System. Some are leaving designated trails and steering onto fragile areas resulting in damage to wildlife and natural habitats, Grijalva said.

A recent meeting of the Sierra Club in Shoshone, Calif., focused much of its attention on the problem.

Officials from the Bureau of Land Management and the U.S. Forest Service declared off-road vehicles a "top law-enforcement problem." They include all-terrain vehicles, dirt bikes, swamp and dune buggies, air boats, snowmobiles and four-wheel drives when used off-road.

Popular recreation areas in Nevada, Southern California, Utah and Idaho are a particular law-enforcement challenge during holiday weekends, said Henri Bisson, deputy director of the BLM.

Both agencies are working to create a system of designated trails and roads that can be used by motor vehicles, Bisson said. They hope clearly marked trails will help keep riders from blazing their own paths.

The BLM employs 195 law-enforcement rangers and 56 special agents, which works out to only one for every 1.2 million acres, Bisson said. The Forest Service has 534 officers and 123 special agents.

Some environmental groups say the problem has become too large for the agencies to manage, and are looking for Congress to step in. They want lawmakers to impose stiffer penalties and increased user fees to repair damaged land.

"Damage to public lands and threats to public lands are so significant that the penalties have to be strong enough to deter illegal off-roading, and that is going to have to be done by Congress," said Daniel Patterson, southwest director of Public Employees for Environmental Responsibility.

Nationally, 64 million acres of forestland are open to vehicles, which has become a problem as the popularity of off-road vehicles has grown, Holtrop said.

"By the time 50 motor vehicles have crossed the same path a user-created trail will likely be left behind that causes lasting environmental impacts on soil, water quality and wildlife habitat," he said.

Brent Eldridge, a rancher and chairman of the White Pine County Commission, said he rides an off-road vehicle to monitor his property. But he sees the damage vehicles can do to the land during a horseback ride up Worthington Canyon.

In testimony he submitted to the subcommittee, Eldridge said the vehicle-based erosion he sees on the West slope of the Schell Creek Range made him a believer of restricting motorized access to federal land.

"The explosion of reckless riding in our area over the past decade is damaging our way of life and creating a backlash against responsible motorized users," he said.

Walls, president of Southern Nevada Off Road Enthusiasts, said the public should be provided with clear, colorful maps of the areas they can legally ride.

He said most off-roaders drive responsibly, on trails and roads or in legally open areas, but that the "5 percent" that do not are ruining it for the rest. He fears any new government vehicle restrictions will be too heavy handed.

Walls said public education can help balance environmental needs with the "intense, crazy, chaotic recreation" that people crave.

During the Sierra Club meeting in Shoshone, discussion was undertaken about individual efforts to identify those ignoring restrictions.

Some were warned that taking photos can backfire into physical assault, while one gentleman noted an incident in which an off-road vehiicle user was all too happy to have his photo taken and even asked for prints.

Also, as has been discovered during unrelated court cases in New Hampshire, photos may not clearly identify an individual rider, causing litigation to run aground.