At Yellowstone's West Entrance, where smog readings regularly flunk federal health requirements, light-headed park employees have had difficulty counting change. Visitors report they can taste the blue haze in this area. Yellowstone officials were forced to enclose ranger booths and pipe in fresh air to curb dizziness, headaches, throat irritation and nausea. Unfortunately, such solutions are not available for wildlife. Air pollution along snowmobile trails which commonly run along rivers and streams releases nitrogen, sulfate and hydrocarbon compounds and increases the acidity of the snow.
Acid snow kills aquatic insects, amphibians and trout.
Trout exposed to hydrocarbon pollution have lower reproductive success, stunted growth and decreased ability to swim against stream currents. Acidity fluctuations may disturb a watershed's natural pH level, damaging the entire ecosystem. Wildlife biologist D.J. Schubert believes that grizzly bears, lynx, elk, wolves, and bald eagles are harmed by snowmobiles. The park recently closed 11 areas to snowmobiles. While wolves abandon snowmobile areas, bison, elk and deer use groomed trails to find better forage, save energy and avoid predators.