The riders had gone up the ridge in the vicinity of the Lahaina Pali Trail, a hiking trail that runs between Ma'alaea and Ukumehame, or along a service road for Maui Electric transmission poles.

State enforcement officers said the riders had passed signs prohibiting motor vehicles on the trail, although at least one of the riders, Toni Marie Davis, 45, of Makawao, protested in a letter that she had not seen any signs prohibiting riding.

The five riders were on state lands outside the forest reserve and did not face criminal penalties. They were cited under Department of Land and Natural Resources rules barring the activity on unencumbered state lands. The Board of Land and Natural Resources approved recommendations for fines and administrative costs at its meeting in Honolulu.

"Motorcycles are an ongoing problem throughout Maui," said Randy Awo, chief of the Division of Conservation and Resource Enforcement on Maui. "There's just more and more people wanting to ride their bikes in environmentally sensitive areas."

State enforcement officers responded to the report of dirt bike riders at Hana'ula Ridge on Feb. 4. Officers had been conducting surveillance of the area after wildlife technician Sasha Smith reported repeated incidents of dirt bike riders cutting through fences, breaking open gates and creating trails across the ridge.

"We're not saying that these people were responsible for the damages that have occurred. But it was what drew us to the area," Awo said. "Sasha was observing and experiencing a great deal of trespassing and damage to the environment."

In addition to Davis, the riders cited and fined were identified as Richard Halfhill, 37, of Kihei, Earnest Kalei Smith, 47, of Wailuku and Randy Waldrop, 50, and Archie Kalepa, 43, of Lahaina.

Awo said the five did not contest the citations at the land board hearing Friday. He said when they have paid the fines, their motorcycles will be returned to them.

John Cumming, Maui District forestry administrator, said dirt bike and ATV riders running illegally off-road in forest reserves and other state lands are creating new hazards and posing a threat to the habitat for native species.

"They create trails that cause erosion and the problem can lead to more damage to native vegetation," he said. "The scarring is permanent. It doesn't go away. It just gets deeper.

"Once those trails get established, they can become real trenches. I've seen some get 3 feet, 4 feet deep. These are some of the hazards, someone could fall in one of those trenches, and there is an impact on the native vegetation," he said.

The Hana'ula area is not the only area affected by illegal riding, he said. Above Kahakuloa, he said, riders are running into the natural area reserve, breaking through fences set up to protect the habitat. Illegal riders also are cutting trails in Kahikinui on the dry leeward slopes subject to heavy Kona storms, where erosion is a more serious threat.

"We've had problems with vehicles all over. They cut through fences, damage the vegetation, even in Polipoli, the Kula Forest Reserve," Cumming said.

The Hana'ula area is particularly sensitive because it includes the nene release pen that is restoring the population of native nene geese to West Maui. Smith said bike riders in December 2005 not only cut through fences around the release pen, but ran over a waterline to the pen.

There are signs posted around the pen, warning against trespassing.

"The riders seem most active in the winter months, which is the peak of our nene nesting season. As I told the board, nene are ground nesting birds, and they are at risk when they are incubating, hatching and molting," she said. "But that does seem to be the busiest time for the illegal dirt bike activity."

Awo said other riders have been cited over the years, but most were caught in forest reserves, where the individuals can be charged in criminal court and the cases were handled in District Court.

But others have evaded enforcement officers. On Feb. 4, Awo said, six other riders were sighted, but enforcement officers were unable to block them from fleeing.