The National Park Service's Winter Use Plan would have allowed 540 snowmobiles to go through in Yellowstone and Grand Teton national parks and the John D. Rockefeller Jr. Memorial Parkway every day, starting this winter.
"According to NPS's own data, the (plan) will increase air pollution, exceed the use levels recommended by NPS biologists to protect wildlife, and cause major adverse impacts to the natural soundscape in Yellowstone," U.S. District Judge Emmet Sullivan said in an order Monday.
Conservationists sued the National Parks Service to stop the plan, saying snowmobiling in the park causes noise and air pollution. They want snowmobiling eliminated in the park, or at least reduced.
Park officials said they averaged about 290 snowmobiles a day in 2006, the most recent number available. Conservationists argued that allowing 540 snowmobiles, a cap higher than that average, would not help solve the park's problems.
"This ruling will restore the quiet and the clean air in Yellowstone for everyone to enjoy," said Amy McNamara, director of the Greater Yellowstone Coalition national parks program.
Added Kristen Brengel, director of the Wilderness Society: "The park deserves to be protected from noise, harm to wildlife and poor air quality."
The judge said letting in the proposed number of snowmobiles "elevates use over conservation of park resources and values." The National Park Service "fails to articulate why the plan's 'major adverse impacts' are 'necessary and appropriate to fulfill the purposes of the park,"' Sullivan said in his order.
The National Park Service must redo the plan, Sullivan said.
Parks spokesman Al Nash said the agency will review Sullivan's decision.
The next winter season begins on Dec. 15. "Our goal is to review this and to see how we move forward for this coming winter," Nash said.
In the late 1990s, as many as 1,400 snowmobiles a day visited Yellowstone, contributing noise and air pollution that critics in Congress and elsewhere said was inappropriate for the country's first national park.