not so bad afterall
Amsnow
A recently conducted study on the Winter Use Plan for Yellowstone National Park again supports responsible, managed snowmobiling to continue in the park.
Recommendations from the Park Service are consistent with the objectives of visitor use and enjoyment found in the National Park Organic Act of 1916. The Environmental Impact Study and comprehensive underlying studies show that continued snowmobile use in portions of Yellowstone and Grand Teton road systems have no adverse impacts on Park Resources, including: Air Quality, Wildlife or Soundscapes.
The proposal put forward by the Park Service is supported by the International Snowmobile Manufacturers Association and is also supported by studies conducted by other related agencies.
The new technologies used today in the manufacturing of snowmobiles are recognized by the National Park Service. Sleds are now environmentally sound and exceed all standards put forth by the US EPA and by the National Park Service Proposed Winter Use Plan.
Many studies have been conducted on the impact of snowmobiles in Yellowstone and Grand Teton on the Bison and Elk Population. Additional scientific studies were conducted on sound and emission standards required by the Federal Government and the Park Service.
The graphs here contain info from the Park Service, which depict the studies findings. Click on a graph to enlarge it.