JACKSON - Snowmobile groups have been mobilizing their supporters to encourage relaxation of some restrictions in Yellowstone and Grand Teton national parks.

Some conservationists say they're concerned the effort by pro-sled groups will reverse progress made in the parks to reduce the impact from humans in winter.

The Blue Ribbon Coalition has sent a steady stream of e-mails to constituents in the last week, encouraging letter writing to the National Park Service. The group encourages people to support provisions in winter use plans that would require only up to 70 percent of snowmobiles entering Yellowstone be guided, down from 100 percent now.

Non-commercially guided sleds where the leader has taken "some type of certification course to lead up to 10 people in the park" should be 30 to 50 percent of daily entries, the group said. And 20 to 30 percent of the daily total should be allowed for unguided snowmobilers, where all group members have watched a video or taken an educational short course.

Several years ago, the federal government released an environmental study indicating the best way to protect the parks' natural resources was to shift from snowmobile to snowcoach travel. Snowmobile groups balked and said that was unrealistic and discriminatory, and worked to retain access to Yellowstone and Grand Teton. Among the compromises made was a switch to sleds with "best available technology," meaning cleaner and quieter, and a guided system where guides could control visitor behavior.

The Park Service is now in the midst of another study to determine to what degree and what type of snowmobile use will be allowed in the park. In the meantime, temporary rules allow for 720 snowmobiles per day to enter Yellowstone with guides, and 140 in Grand Teton. Machines must be cleaner and quieter. The plan is slated to be in place through the winter of 2006-07.

Jon Catton, a Bozeman, Mont.-based conservationist, said the Blue Ribbon Coalition wants to "turn back the clock" and reverse the progress made to clean up the parks.

"This narrow-minded tactic by the Blue Ribbon Coalition - to browbeat the Park Service to reverse recent gains for visitor health and safety - is indifferent or contemptuous toward the health and enjoyment of national park visitors and those who work there," he said. "It's a self-interested position that goes against the long history and tradition of our national parks, which puts protecting parks and the interests of all visitors first."

Jack Welch, chairman of the Blue Ribbon Coalition, wrote in an e-mail that the Blue Ribbon Coalition understands the Park Service is considering alternatives ranging from "all guided access" to "some guided," and asked members to encourage the agency to give "meaningful" consideration to its proposal. The group also wants snowmobilers to have access to the same overlooks as do snowcoaches.

In Grand Teton, the Blue Ribbon Coalition is encouraging the Park Service to allow "non-best available technology" snowmobiles.

Welch said the requirement for four-stroke sleds in Grand Teton is "totally ludicrous" and "overkill."

The group's e-mail said managing Grand Teton separately from Yellowstone for winter use has never been carefully considered, and should be.

The group wants non-best available technology sleds to be able to operate on the Continental Divide Snowmobile Trail, as people may come from Lander or other areas and link up with the trail, and they should not have to switch sleds. And, "100 percent of this trail is immediately adjacent to plowed highways used by other motor vehicles," the group said.

Non-best available technology snowmobiles should be allowed on Jackson Lake, and from Flagg Ranch on the Grassy Lake Road to connect to trails on the Targhee National Forest, the group said.

Welch said the "linkage" routes in Grand Teton are key for snowmobilers, and if the linkage goes away it will affect tourism.

"We sincerely want Grand Teton National Park to assert themselves in this process and not just be drug along by the whims of Yellowstone folks," Welch said.

Bob Seibert, a ranger in West Yellowstone for 14 years who retired last year, said even with the changes being proposed by some groups, the direction Yellowstone should take continues to be a phaseout of snowmobile use.

"The fact that that process has been so drastically interfered with from political agendas… It is a dangerous precedent to move forward with additional compromise," he said.

Seibert also said park conditions after guides were required "were significantly improved," as guides could tell people how to avoid disturbing wildlife and forced visitors to reduce speeds. It also reduced noise, as groups were clustered and there were moments of quiet between groups.

Of the snowmobile groups' push for looser restrictions on guiding, Seibert said, "Any time they see a weakness or a potential to expand back to the way it was, they latch on to it. Now they want to do that with the guiding requirement."

Loosening requirements for visitors to travel without guides may be difficult. Last year, Interior Secretary Gale Norton and Park Service Director Fran Mainella both said publicly part of the success of the new winter use program was requiring people to travel with guides.

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