Since the 1960s, the use of snowmobiles has steadily grown into a popular sport that is sparsely regulated, especially on public lands. No thorough environmental impact study of their effects has been undertaken.
About 1.3 million snowmobiles are registered in the USA. A typical owner rides about 1,600 km each winter. The bigger machines can easily surpass 150 kph.
A major drawback of snowmobiles is exhaust pollution, which collects in the snow and eventually flushed into the watershed. There is considerable noise pollution also. The stronger machines allow riders to get higher into the mountains. That infiltration not only jeopardizes permanent wilderness status for some roadless areas but disrupts sensitive wildlife species such as wolverines, Canada lynx and herds of elk.
Before snowmobiles were allowed into Yellowstone National Park, USA, bison remained in the park's interior. In 1997, over 140,000 snowmobiles traverse the park on groomed trails, which also provide the bison easy routes for access to more hospitable areas outside the park. Because the bison can carry brucellosis, they are either shot when they approach private property or trapped and taken to slaughterhouses if they test positive for brucellosis. More than 800 animals were killed in 1997. Ironically, the easy movement that the winter trails provide has allowed more bison to survive rough winters, leading to overpopulation of the herds.