As Minnesota maps a vast system of all-terrain vehicle trails, the state is confronting the incendiary conflict between motor use and quieter outdoor recreation.

Yet the state lacks a formal policy on divvying up the forest among motorized and non-motorized uses.

"We're looking at what [forest routes] can sustain motor use and we're closing that which can't," said Brian McCann, recreation planner for the state Department of Natural Resources. "It hasn't been based on any formula or pre-conceived notion as quotas or percentages of how they're used."

Wisconsin's DNR, which studied the issue in 2006, concluded "it is evident that ATV riding is incompatible with every other land-based activity but snowmobiling."

The Minnesota DNR surveyed 4,400 people in the state about outdoor recreation in 2004 and found about 10 percent said they used ATVs off road.

Some who use state forests for horse riding, canoeing, camping and bird watching say they have already been driven out of the woods by motors.

Kate Crowley and her husband, Mike Link, wrote a book on hiking in Minnesota. But they seldom set foot on the state forest trail closest to their home outside Willow River, Minn., because of the noise from ATVs and dirt bikes, especially on weekends.

"I just avoid it," said Crowley, a naturalist who has co-authored 15 books, including "Hiking Minnesota."

George Carleton and his wife, Harriett, no longer visit the campground they had enjoyed for years in Land O' Lakes State Forest. More ATVs and dirt bikes made the camp noisy and campers feel unsafe. On Labor Day weekend in 2007, a driver on a yellow dirt-bike roared by children riding tricycles.

"In three minutes he terrorized the entire campground," Carleton said. "We made a simple choice: we lose, you win."

Len Hardy, first vice president of the state's ATV rider association, said that conflict between motorized and non-motorized users is exaggerated by people who spend little time in the forests. "They say they're environmentalists, but they just want to complain," Hardy said. "When you really pin them down, they just don't want anyone out there in the woods."

Forrest Boe, the DNR's trails and waterways director, said conflict exists, but noted that state forests have long allowed vehicles. He said that people who don't want to hear engines when they hike, ride horses or pick berries may need to choose places without motorized trails or go on weekdays, when off-road traffic is lighter.

"I think in general they can live together most of the time," Boe said.

TOM MEERSMAN • 612-673-7388 meersman@startribune.com DAVID SHAFFER • 612-673-7090 dshaffer@startribune.com