Snowmobiles--a form of motorised bobsleigh--are being used increasingly in the famous Yellowstone National Park in Montana to view scenery and wildlife. The machines are used on trails that would otherwise be inaccessible, except to walkers and skiers.

But conservationists are worried that the snowmobiles cause damage to the environment, packing down snow to hard ice that inhibits plant growth and animal movement, and even causing soil erosion on well-used snowmobile tracks. Noise pollution is often considered the major problem. The air-cooled engines make as much noise as a motorbicycle, and ecologists claim that the machines unnecessarily disturb wildlife.

Legislation to restrict the use of snowmobiles had already been passed in Canada, from where a large number of snowmobiles are imported to the United States. Conservationists are attempting to introduce similar laws in the U.S.

But despite the protests, snowmobiling is still one of the fastest-growing sports in North America. Already this year, 7,000 snowmobiles have passed through Yellowstone Park--an increase of 15 per cent over last year.

SYNOPSIS: In the United States" Yellowstone National Park of Montana, snowmobiles, or motorised bobsleighs, are becoming an increasingly popular sport. Groups of snowmobiles tour the park almost daily, making light of conditions that wold bring normal transport to a standstill. Making use of lightweight, aircooled engines, the machines can travel over ground previously only accessible to walkers.

The famous hot springs of Yellowstone can be reached by snowmobilers through some of the deepest snow-drifts, and for wildlife lovers, use of the machine can be rewarding.....

But there are opponents of snowmobiles. Conservation groups look upon the machines, not as a sport, but a menace. They claim that snowmobiles pack down the soft snow, destroying young plants and restricting wildlife movement.

They also say that wildlife is unnecessarily disturbed by the machines, which produce as much noise as an unsilenced motorbicycle. Legislation to restrict the use of snowmobiles has already been passed in nearby Canada, and U.S. conservationists are pressing for similar laws.

Meanwhile, snowmobiling continues to be one of America's fastest-growing pastimes.