Water Pollution
Air Pollution
Noise Pollution
Spread of Weeds
Destruction of Plant Communities
Soil Compaction and Erosion
Disruption of Wildlife and Destruction of Wildlife Habitat
Impacts on Cultural Resources

Water Pollution

Two-cycle engines—common in most jet skis, snowmobiles, and other thrillcraft—are notorious polluters. The typical jet ski dumps an average of 3 gallons of gasoline directly in the water for every hour of operation. Indeed, jet skis release 8 times the amount of fuel as an equivalently horsepowered motorboat. Snowmobiles dump approximately 30% of their fuel out the tailpipe into the snow, including highly persistent polycyclic aromatic hydrocarbons which are then frozen into the snowpack. When the snow melts in the spring, a concentrated surge of pollutants contaminates ground water and surface water that can harm aquatic insects, amphibians and fish, not to mention human water supplies.

Other land-based machines like dirt bikes, four wheelers, and swamp buggies tear up soil contributing to soil erosion which ultimately winds up degrading water quality.

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Air Pollution

According to the California Air Resources Board, a typical two-stroke snowmobile engine produces as much harmful pollution in seven hours as a passenger car driven for 100,000 miles! The newer four-stroke engines are not much better. Pollutants for all snowmobiles emitted include carbon monoxide, benzene, and formaldehyde.

According to EPA, thrillcraft produces13% of the hydrocarbon emissions from all mobile sources annually, including approximately 5 million tons of carbon monoxide, nearly 1 million tons of hydrocarbons, 340,000 tons of nitrogen oxides, and 8 thousand tons of particulates.

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Noise Pollution

Noise pollution, or noise litter, is one of the major impacts of thrillcraft on other people. Snowmobiles in Yellowstone, for instance, can be heard more than 2 ½ miles away. That’s a corridor 5 miles wide where silence is compromised by thrillcraft. Silence is an increasingly rare commodity in today’s world, and one that should be protected on public lands. Studies have shown that typical thrillcraft decibel levels are harmful to human ears.

But they may also be harmful to wildlife. Many wildlife species depend on hearing to detect predators, find prey, find mates (as in bird song), and other critical biological functions. Noise from thrillcraft has been found to cause erratic behavior, bleeding from the ears, and hearing loss in kangaroo rats.

The noise from thrillcraft can also affect habitat use by wildlife. In one study in Oregon, elk were found to respond to (by moving away) and avoiding thrillcraft use areas by more than a half mile, potentially removing a corridor of habitat up to a mile wide.

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Spread of Weeds

The spread of exotic weeds is one of the most insidious threats to our public lands. Weeds typically colonize disturbed sites where the native vegetation has been weakened or removed. Thrillcraft, by trampling and tearing vegetation, as well and creating bare soil, facilitates the colonization of land by weeds. Plus, thrillcraft transport seeds from place to place, carrying seeds in mud clumped on wheels or attached to the chassis. One study found 1700 knapweed seeds on a vehicle after it had only backed up 40 feet. Ten miles later 8% of those seeds were still attached. Water thrillcraft, like jet skis, can also transport aquatic weeds like Eurasian watermilfoil.

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Destruction of Plant Communities

One obvious impact of concentrated ORV use is the destruction of plant communities. By tearing, trampling, compacting, and removing plant cover, thrillcraft damage plants from grasses to trees. These impacts in turn can lower plant diversity, plant cover, and plant vigor.

Damage to plant communities can also result from toxins and pollutants released by machines. For instance, snowmobiles leak fuel into the snowpack which then melts as a concentrated flush in the spring.

One of the most important vegetative covers in desert areas are biological crusts. These algae and lichen crusts fill the spaces between plants, binding soil, capturing free nitrogen in the air and transferring it to soils, and acting as a mulch to retain soil moisture. These crusts are extremely vulnerable to trampling from thrillcraft. They may take hundreds of years to full recover.

Loss of plant cover can lead to increased soil temperatures, which in turn can affect soil fertility, hydrological processes, and soil micro-fauna.

Beyond the physical destruction of plants, the other way thrillcraft destroys plant communities is by facilitating invasion by alien species by weakening the native plant communities and the transportation of invasive seeds. The end result is the biological impoverishment of the plant community.

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Soil Compaction and Erosion

Because of their weight, thrillcraft compacts soils, reducing the interspaces between soil particles. As soils become more dense and less porous, permeability by air and water decreases, disrupting water infiltration, leading to droughty conditions for sub-soil, and increases surface flow volume and velocity, which in turn creates greater soil erosion potential as well as flooding.

Soil compaction can also harm soil microflora and microfauna affecting nutrient cycles, and soil fertility.

Heavy ORV use can also crush and damage tree root systems as well as soil microbes, insects, and other animals that live in or use the upper layers of the soil profile.

On steeper slopes which are often favored by thrillcraft enthusiasts, soil erosion is increased significantly. Soil movement downslope can bury other vegetation and/or move into streams where it negatively impacts aquatic species including fish. One study estimated that sedimentation from ORVs had reduced game fish populations by 90% due to negative sedimentation effects upon aquatic invertebrates upon which the fish feed, reduction in fish spawning habitat, and oxygen supply.

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Disruption of Wildlife and Destruction of Wildlife Habitat

Thrillcraft are responsible for three major impacts on wildlife. Disturbance and noise affects many species, from grizzly bears to toads. The mere presence of machines, particularly those moving in unexpected ways (i.e. not a highway) has been shown to increase stress and energy loss as animals strive to move away from vehicles. Elk, for instance, ran when approached within 2000 feet by thrillcraft, but did not move until a human on foot approached within 500 feet. Another study of grizzly bear shows that bears used habitat close to roads less than expected, and researchers calculated that road use eliminated more than 8.7% of total habitat. This avoidance behavior by bears occurred even when motorized use was no more than a few vehicles a day.

Direct mortality is a problem where animals are run over or otherwise collide with thrillcraft.

Thrillcraft can also destroy wildlife habitat. The nests of ground nesting species are crushed, while burrows of subsurface dwelling animals, like the desert tortoise, are collapsed by thrillcraft. Thrillcraft also provides access for hunters and poachers. One study of wolves in the Rockies found that 21 out of 25 human-caused mortalities were within 600 feet of a motorized trail.

Finally, thrillcraft use fragments wildlife habitat much the same way that roads do, except given their often higher density, the impacts are worse. Fragmentation of habitat reduces the amount of land available for feeding, resting, denning, and use as travel corridors. All of these factors are cumulative and ultimately reduce individual fitness and can negatively affect wildlife populations.

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Impacts on Cultural Resources

In the four corners region of the southwest, ORV use is leading to increased levels of vandalism and looting of ancient archaeological ruins. In other parts of the country, historic cabins, pictographs, ancient campsites, and other cultural resources are in jeopardy for the same reason—easy access makes it easy to damage, intentionally or unintentionally, these valuable cultural sites.

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Published . . . . .
Foundation for Deep Ecology
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Distributed . . . . .
Chelsea Green, Nov. 2007
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Edited by . . . . .
George Wuerthner

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George Wuerthner
Foundation for Deep Ecology
Building 1062, Fort Cronkhite
Sausalito, California 94965
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Copyright 2008 - Thrillcraft :: The Environmental Consequences of Motorized Recreation

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