Yellowstone National Park, famous for its steaming geysers, bubbling mud pits and herds of bison and wolves, is considered a crown jewel in the U.S. National Park System. But Yellowstone is at the center of a fierce political battle over a new decision to permit the continued use of snowmobiles in the park.

This is the sound that has stirred up so much debate in Yellowstone and Grand Teton national parks in the American West. For years, noise and fumes from thousands of gasoline - powered snowmobiles have sparked complaints from winter visitors and park employees. Some rangers working near heavy snowmobile traffic have had to wear respirators and hearing protection. The snowmobile situation, many people have argued, is out of control.

After an environmental impact study and 22 public hearings around the country in the final years of the Clinton administration, the Park Service issued a regulation to phase out snowmobile use in Yellowstone National Park.

But before that ban could go into effect, snowmobilers had a new friend in the White House President George W. Bush. They sued the National Park Service to cancel the planned snowmobile phase-out. The White House ordered a second environmental impact study. The results, published February 20, call for a reversal of the proposed snowmobile ban.

Bill Horn represents a coalition of snowmobile groups. He calls the Clinton policy to ban snowmobiles "arbitrary and capricious." "It wasn't based on facts.," he said. "It was based on politics, pure and simple. When you look at the facts, 65,000 snowmobiles using the road system don't have any more adverse impact on the resources of Yellowstone Park than do 1.5 million automobiles, buses and trucks using that same road system seven or eight months of the season."

The Park Service's reversal will establish new rules for snowmobile use in the park. These rules will require most snowmobilers to join guided tours, and within two years, to drive only vehicles with newer, quieter and less polluting engines.

Steve Bosak is the Associate Director for Park Recreation for the National Parks Conservation Association. He says the plan is not in the best interest of Yellowstone.

"If you look at the first studies that the Park Service did before the Bush administration came in, they had already considered new snowmobile technology," said Steve Bosak. "A lot of what the snowmobile industry gave them was not new information. And if you look at what the EPA [Environmental Protection Agency] has said about this whole process, they say it is clear that the best option for protecting the environment, for protecting the wildlife, protecting the visitors and the employees in the park is a ban on snowmobiles."

The controversy has generated more mail than any issue in Park Service history. 80 percent of the 350,000 letters favored a ban. Steve Bosak with the National Parks Conservation Association argues that snowmobilers have other options in the vast stretches of Wyoming, Montana and Idaho, of which Yellowstone Park is only a small part.

"You can go snowmobiling outside of Yellowstone, just outside of Yellowstone on hundreds of miles of trails just in that vicinity, 14,000 miles (22,500 kilometers) of trails in all of those states, and there are 180 miles (290 kilometers) of park trails where you can enjoy the park without snowmobiles and you can see the bison, the elk, the wolves, the eagles and not hear that buzz of snowmobile engines," he said.

Steve Bosak says those 290 kilometers in Yellowstone are threatened by the current action.

Bill Horn, the lobbyist with the snowmobile coalition, disagrees. He says snowmobiles stick to limited routes already in place and do not violate pollution laws. He fears a snowmobile ban in Yellowstone could lead to even greater restrictions.

"If the determination is made that 65,000 snowmobiles create this unacceptable environmental damage, then there is absolutely no way you can continue to permit the million plus automobiles to enter that park every summer," said Bill Horn. "And so the summer users need to be completely appreciative of the fact if you lose the snowmobile access on the road system, trust me, the same groups went after the snowmobiles are going to be coming after automobile use in the summer time."

Steve Bosak with the National Parks Conservation Association believes that in the short-term, Yellowstone will be hurt by the Bush administration policy. But he believes the rules can be reversed by U.S. Congressional legislation. He expects that the Yellowstone Protection Act which would ban snowmobile use in the park - will be introduced in the U.S. Congress sometime this year.