Hikers hate to see a good trail go bad.

When the forces of nature or the hands of humans wreck a trail, hikers feel sad. Somewhere out there, back of beyond, is a swimming hole or a summit, a shady sycamore grove or the ruins of an old mine that can no longer be visited.

These days, a lot of longtime trail users are upset--or at least uneasy--about the state of the Southland's trail system.

Gone are Monrovia Peak Trail, Tom Sloan Trail and more trails in the Angeles National Forest.

Gone are Roque Canyon Trail, Horse Gulch Trail, Sespe Creek Trail and more in Los Padres National Forest.

"How do I find the trails in the Santa Monica Mountains?" asks veteran hiking guidebook writer Milt McAuley. "By parting the brush."

McAuley is only half-kidding. No one knows exactly how many trails are lost to neglect or mismanagement, but many trail experts say the state's trail system is heading downhill.

According to a recent report by the U. S. General Accounting Office, the use of national forest trails rose by one-third during the 1980s while funding fell by 39%. Other statistics:

* Walking for exercise is by far California's most popular form of outdoor recreation, yet only a handful of county, state and federal parks allocate even 1% of their annual operating budgets for trails.

* In California, about 7,000 miles of national forest trails need work or reconstruction at an estimated cost of $27.6 million.

* In fast-growing Southern California, trail-building is lagging far behind trail use. In San Diego County, for example, bias against trails in the county's general plan has meant that only four miles of new trails have been dedicated since 1982.

"It's a moment of truth for trails," said long-time trails advocate Tony Look at the recent annual meeting of the California Recreational Trails Commission.

"We have to raise consciousness about trails, particularly in Southern California, before we lose more of them, or ever hope to build more."

Protecting old trails and promoting new ones is the mission of the five-member California Recreational Trails Committee, whose members are appointed to four-year terms by the governor. The committee receives a small amount of logistic and clerical help from the state Department of Parks and Recreation. As a political body, the trails committee is powerless; however, as a cheerleader for the state's trail groups and as a clearinghouse for trails strategy, the group serves a useful function.