JACKSON - Conservation groups announced Wednesday they would seek a court review of the National Park Service's decision to allow continued snowmobile access in Yellowstone and Grand Teton national parks.

A court review means a court would re-examine the case to ensure it complies with applicable laws - essentially, an appeal. A court has to agree to the review.

The groups announced their intention one day after the Park Service announced a final decision to allow 540 sleds per day in Yellowstone. Conservation groups have long advocated the best way to protect the park's natural resources is to shift from snowmobile access to snowcoaches only - a position also supported by the Park Service's own scientific studies of the impacts of snowmobiles.

The groups said the decision to allow snowmobiles ignores the Park Service's overarching mandate to give highest priority to conservation of national park resources.

"The past four seasons have shown that Yellowstone's winter visitors are increasingly embracing modern snowcoaches, and the health of the park has improved because of it," Amy McNamara of the Greater Yellowstone Coalition said in a release. "The National Park Service's decision makes a U-turn on that progress and will lead to unacceptable impacts in our first national park."

A snowcoach is a van mounted on tracks.

News of litigation did not come as a surprise to most who have been following the issue for more than a decade.

Jack Welch with the Blue Ribbon Coalition, a group involved in advocating for continued snowmobile access in the parks, said he was disappointed because of the continued "arduous" scientific process and the changes the agency has accommodated in creating the latest plan.

"The conservation groups are not satisfied with anything other than no snowmobiles in the park," he said.

Welch said his group, too, is not totally satisfied with the final decision, in part because of a guiding requirement. Visitors to the park must go with commercial guides, and Welch said people who take training courses should be able to lead private groups.

He also said it's not likely the final decision signed this week - and expected to become law in time for Yellowstone's winter opening Dec. 19 - is the end of the road.

In a release, conservation groups chastised the Park Service for increasing the number of snowmobiles authorized to enter the park from what has been the average for the last three winters. Even with those lower numbers, monitoring has shown unacceptable impacts to air and sound quality in the park.

Groups say there are also unacceptable impacts to wildlife.

"After a three-year study, the park's own scientists recommended capping traffic at its much-reduced level to protect winter-stressed animals from being disturbed and harassed by too many vehicles," said Chris Mehl of The Wilderness Society. "Instead of heeding its scientists, the Park Service has elected to double snowmobile use from those levels."

Park Service Intermountain Regional Director Mike Snyder, who signed the final decision Tuesday, has said the reason some levels were exceeded in recent years is that some snowmobiles entering the park were "administrative" sleds that didn't use best available technology. He also said some snowcoaches were not using such technology.

Sleds will be required to have best available technology starting next winter, and the requirement will apply to snowcoaches starting in 2011.

The new park rules go into effect next winter. This winter will operate under temporary rules, allowing 720 sleds a day. About 280 sleds have entered Yellowstone on average in the last three years.

The conservation organizations challenging the decision are the Greater Yellowstone Coalition, National Parks Conservation Association, The Wilderness Society, Natural Resources Defense Council, Winter Wildlands Alliance, and Sierra Club.

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