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.
Snowmobiles also disrupt the courtship and survival of bald eagles.
Montana is practicing hypocrisy. They want the economic benefits, but not the snowmobile destruction they can't have it both ways. Presidents Nixon and Carter anticipated the snowmobile controversy. Nixon required land managers to assess snowmobile use. Carter strengthened the provision by imposing an immediate ban until further studies could confirm that snowmobile use would not harm the national parks.