JACKSON - Conservation groups Tuesday appealed a U.S. Forest Service decision continuing helicopter skiing in areas of northwest Wyoming.

The groups say Bridger-Teton National Forest officials' plan allowing a boost to historic helicopter skiing levels and the presence of the activity in wilderness study areas needs to be re-evaluated, but did not say the activity should be eliminated.

Crucial big game habitat and wolverine denning habitat should be protected, and no net gain of flights in the wilderness study area should be allowed, the groups said.

Tom Darin with the Jackson Hole Conservation Alliance said the 1984 Wyoming Wilderness Act requires forest managers to maintain wilderness qualities. He said increasing numbers on a permit where a majority of activity takes place in the Palisades Wilderness Study Area is not in keeping with that law.

"We said, 'Let's try to keep the level of use at 1984 levels and then try to spread some of this business out to adjacent areas,'" Darin said. "We don't think (the plan) tried to do that balance at all."

Wilderness study areas are not the same as designated wilderness - where some types of human activity are restricted - but generally are managed to protect wilderness values.

Bridger-Teton National Forest officials agreed to allow High Mountain Heli-Skiing 832 skier days per season, plus an additional 368 days "as needed," to allow for company growth.

The company's highest use has been 903 skier days, a number based on individual skiers over the course of the season.

In the past, the company has averaged about 750 skier days per year. High Mountain Heli-Skiing received a permit on the forest in 1977, and the forest issued special-use permits every five years. The last permit expired in December 2001, and one-year, temporary permits were issued in 2001, 2002 and 2003 to allow the company to continue while the environmental analysis was completed.

Other choices considered in the analysis would have bumped the number of days to 1,500, lowered the number to 468 and eliminated the activity altogether.

But conservation groups say alternatives restricting the company's flights in wilderness study areas were not adequately considered.

Darin said the only variable changed was the number of skier days. Instead, the agency should have considered eliminating the activity in the study area, or scaling it down.

"We were trying to think of alternatives that were reasonable that considered the geographic scale," he said. "They really didn't make that effort, and we think that right up front violated the (National Environmental Policy Act) statute."

The agency said in its decision that allowing heli-skiing in the wilderness study area does not preclude the area's future inclusion in the National Wilderness Preservation System. Over-the-snow activity will not alter the wilderness character, the agency said.

In general, the agency said, only one helicopter per day will be allowed in the area.

But Darin said based on historic levels, 99 percent of the heli-skiing activity occurs in the study area.

"We're concerned that the historic trend is going to follow, and all the use will be in WSA," he said.

Heli-skiers have said their only impact is tracks in the snow that eventually melt away. Skiing is a quiet activity and has no more impact than people hiking in the area, they said.

Representatives of High-Mountain Heli could not be reached for comment Tuesday.

Conservation groups have also questioned why the Forest Service is not doing more to protect wolverines in the area. A wolverine expert told the agency wolverine denning habitat is in the area and will be affected by helicopter skiing.

Groups filing the appeal were the Jackson Hole Conservation Alliance, Greater Yellowstone Coalition, Sierra Club, Wyoming Wilderness Association and the Predator Conservation Alliance.

Environmental reporter Whitney Royster can be reached at (307) 734-0260 or at royster@trib.com.