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Tales of Trails

by Kristi Withrow

For a long time, arguments were made that public lands needed to be saved from logging and mining so that people could enjoy them. It was realized that public lands had recreational value as well as economic and extractive values. Now a new perspective is emerging. People are realizing that even recreation can pose risks to the natural and biological values of public lands.

According to Roz McClellan of the Southern Rockies Ecosystem Project, outdoor recreation, especially motorized and mountain bike recreation, is the fastest-growing use of Colorado's public lands. This type of recreation tends to increase the number of people on trails, which in turn leads to the need for more trails. So what? Theoretically more trails would spread out use and cause less environmental impact per mile of trail. Well, not necessarily.

Trails introduce what biologists call fragmentation and edge effect. Many species require large roadless areas for their survival. Some birds and small mammals will not cross roads or trails because the openness leaves them more susceptible to predation. The more trails present, the less habitat these species have, and they can become separated from other populations of their species. Denis Hall of High Country Citizens' Alliance likens this to someone building a road or trail through your living room.

This would be bad enough, but now imagine that for some reason you are isolated from friends or family members on the other side of your house. Your habitat has become effectively fragmented. Not only do roads and trails themselves destroy what is called "habitat effectiveness," but biologists claim that the effects of roads and trails can extend out 100 meters on either side of a trail, leaving a 200 meter wide corridor of degraded or ineffective habitat.

Edge effects are harmful to plants and animals that need unfragmented interior habitat. These "interior species" are not adapted to the edges of areas created by roads. They may be further harmed by new species introduced through these travel ways--exotic species. Exotic plant species may be introduced by seeds carried in on hiking boots, pets or tires. Exotic species are often well adapted to disturbance and can therefore thrive in these areas at the expense of native plants by taking over their soil and nutrients.

An example of exotic animal species is the cowbird. Cowbirds tend to be present along edges, such as trails and roads. They are nest predators, laying their eggs in the nests of other birds. When the cowbird eggs hatch, the young push out the other eggs and the cowbird young are then raised by the original nesting pair, spreading cowbirds and reducing the numbers of native species.

Trails are harmful also because they introduce pollution, such as exhaust from off-road vehicles. Increased presence of humans also increases stress among animals, which reduces reproductive success and survival of the animal. Studies show that parents provide less post-natal care to their young in areas with more human intrusion.

We can reduce our impact by doing a few things. Trails should be developed along established corridors of roads and existing trails. By using existing corridors and concentrating use in them, we can help to avoid fragmenting previously undisturbed habitat. Riparian areas are especially susceptible to the effects of trails. These areas and other sensitive habitat should be avoided. We can educate ourselves and others about our impact on trails, which can also help mitigate our effects.

Last summer a number of individuals and groups documented the impact of trails. This work ranged from scientific studies along trail corridors to photographing areas where the trails or surrounding areas have been affected by use. This documentation will be compiled and used to find ways of mitigating the impact of trails.

What You Can Do: To learn more about the impact of recreation on trails or if to get involved in documenting trail and resource damage, call the Southern Rockies Ecosystem Project at (303) 447-9409.

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