After five years of meticulous mapping, Minnesota is on the verge of ensuring that thousands of miles of backwoods trails and roads are open to all-terrain vehicles.

It will be the state's biggest step yet to gain control over ATV riding in its public forests, and it's stoking a contentious debate over what place motors have in the woods.

The immense trail project will have lasting consequences for outdoor recreation in Minnesota. It also is bitterly dividing the state Department of Natural Resources, which manages 4.2 million acres of state forests.

Some DNR experts are worried that the changes will leave forests and other wild lands vulnerable to damage from ATVs.

Others call the newly sanctioned trails, which could exceed 7,700 miles, the best way to control what had been a motorized free-for-all on public land.

In shaping the plan, top DNR officials repeatedly overruled field staff by approving motorized access near riverbanks, bogs and old-growth forest, and in areas that harbor red-shouldered hawks and rare plants, interviews with DNR staff and a review of agency records show.

The agency says riders tend to stay on marked trails. It contends there is no need to route trails away from wetlands and other critical areas that can be ravaged by the wheels of wayward ATVs.

"We're trying to give the users the benefit of the doubt, instead of the agency coming out and always saying 'No, no, no, no, no, no, no,'" said Bob Leibfried, DNR regional manager for ecological services.

But many of those who camp, fish, canoe, watch birds and ride horses on public lands are finding those pursuits less enjoyable or impossible in the presence of noisy and fast-moving off-road vehicles.

"You don't mix motorized recreation with a wild experience. You can't have it," said Matt Norton, forestry and wildlife advocate for the Minnesota Center for Environmental Advocacy. "One is going to lose out. Guess which one that is going to be?"

ATV rider groups say they deserve trails in state forests because four-wheelers are excluded from wildlife management areas, most parks, the Boundary Waters Canoe Area Wilderness and other public lands.

Riders generally give the DNR high marks for its mapping work. Len Hardy, first vice-president of the All-Terrain Vehicle Association of Minnesota, said rider clubs in the state want a completed trail system. He sees it as a way to repair the scars, rather than cause more.

"We've been riding on these trails now for 20 years, some of them, and nothing's ever been done to them," he said. "We know there's damage out there."

Once a trail system is determined, Hardy said, clubs will be able to apply for state money to fix the problems.

'We failed as an agency'

The sweeping trail survey has its roots in a debate that flared six years ago. In 2002, the Star Tribune reported that ATVs and four-wheel drive trucks were running off trails into wetlands and gouging hillsides in many forests and wildlife management areas, including one of the first motorized trails in the state, the Spider Lake Recreation Area northwest of Brainerd.

The Legislature ordered the agency to get control of the situation at Spider Lake and elsewhere by taking inventory of roads and trails in all 58 state forests and, by the end of 2008, identifying routes where off-road enthusiasts should be allowed to drive.

"We failed as an agency in the management of ATVs," said DNR Commissioner Mark Holsten. He said the situation has improved significantly in the past five years. Holsten became deputy commissioner in 2003 and commissioner in 2007.

"My job is to bring some order to an unordered world," he said.

The trails in question are already there. Almost all were blazed over the years by loggers, hunters and, more recently, ATV riders who went wherever they wanted in the state forests.

The DNR spent $2.3 million to map all roads, trails and other corridors in state forests. Then the agency assigned teams of experts from various divisions, including trails and waterways, forestry, fish and wildlife, enforcement and ecological resources, to recommend which routes remain open in each forest. After holding public meetings and reviewing citizen comments, the commissioner makes the final trail decisions.

So far, the DNR has approved about 3,300 miles in 33 forests as open for recreational riding and closed 2,070 miles. The DNR expects to close about 1 mile of trail for every 2 miles kept open. When the remaining 25 forests are approved later this year, the state could end up with 7,700 miles of recreational routes.

Wisconsin, by contrast, has about 180 miles of ATV trails on DNR land, and its state forest system is about one-eighth Minnesota's size.

"Here in Wisconsin, our lands were designated as closed to ATVs until we decided to open some of them," said Steve Petersen, DNR superintendent of Northern Highland-American Legion State Forest in northern Wisconsin. "That's different than Minnesota where initially everything was open to ATVs and now you're trying to close some trails."

Most ATV riding in Wisconsin is on county lands, he said. Minnesota also has thousands of miles of trails and roads open to ATVs in county and federal forests.

Ideas were rejected

If it had been up to some DNR trail planning teams, many more places would be off-limits to ATVs.

Teams recommended closing areas to ATVs to protect nearby wetlands and other natural resources, but top DNR managers repeatedly ordered revisions that favored motor access.

Mike North, a DNR ecologist who reviewed motor policies in north-central Minnesota, said it only takes a few riders illegally driving off the trail and "the next thing you know you can have some pretty significant wetland damage." Other agency experts said they feared for their jobs if they spoke out publicly about such concerns.

• In Sturgeon River and Crow Wing state forests, planning teams recommended 50 areas where even hunter use of ATVs would be banned. These areas included wetlands with rare plants, pristine lakes and old-growth hardwoods. Top DNR officials have overruled 80 percent of the closures, allowing hunters to drive ATVs off-trail at certain times.

• In Mississippi Headwaters State Forest, which features 40 miles of near-wilderness riverfront, three of the five planning team members recommended that the entire forest be closed to off-trail riding because of sensitive soils and past illegal ATV riding in the river. DNR Regional Director Mike Carroll in Bemidji kept part of the forest open to ATVs.

• In Nemadji State Forest, on the Wisconsin border in Pine County, the planning team proposed to close a trail that borders an old-growth forest containing rare plants. DNR managers rejected the closure, saying someone would have to prove the trees and plants would be harmed before they took such an action.

• In Cloquet Valley State Forest, north of Duluth, DNR's team recommended that dozens of trails that dead-ended at wetlands be closed. DNR managers rejected that advice, saying riding off-trail into wetlands is already illegal, and closing trails near them would be "layering on" regulations.

Top DNR officials said it's no surprise that some ideas were challenged and overruled. Holsten, the DNR commissioner, said he wanted specific reasons to tell the public why trails needed to be closed, such as proof that unique natural features needed extra protection.

"We asked hard questions," Holsten said of his meetings with experts. "We asked them to look at it from this perspective, and none of them looked at it from that perspective."

The DNR still is considering how many areas should be limited to hunting on foot and whether all recreational trail riding should be banned during the firearms deer season, officials said.

Costs not considered

Jim Weseloh, once a Grand Rapids-based planner for DNR, said he retired last year rather than continue with a process he thought was leading the agency into trouble.

Weseloh said agency managers had a goal of keeping as many trails open as possible. When planning team members brought up costs to maintain trails or enforce rules, he said, they were told: "Don't worry about that."

Forrest Boe, director of DNR's trails and waterways division, said that the maintenance costs were not considered because the five-year planning effort focused mainly on environmental issues.

At two heavily used ATV trails -- Spider Lake and the 25-mile Red Top Trail just east of Mille Lacs Lake -- the state has spent about $650,000 to deal with erosion and other damage since 2002. Even so, both trail systems need more work.

Foresters who checked on Spider Lake in June concluded that one trail segment, "will continue to cause serious erosion, cutting, and damage to the trees themselves" without repairs. In July, parts of the Red Top trail were in such bad shape that Aitkin County, the main landowner, closed segments until they were renovated.

Boe said maintenance costs will depend on such factors as how many riders use a trail, whether it is susceptible to erosion and the frequency of storms that saturate soils and down trees. Holsten said the DNR will look closely at costs and other issues.

"This isn't a trail designation system that's locked down in granite forever," Holsten said. "It will be under constant analysis and review once it's put in place."