Wildlife And Trails Primer - B. Avoiding large natural areas

Planning Trails with Wildlife in Mind

Protecting large, undisturbed areas of wildlife habitat should be a priority. Deciding whether or not to build a trail that may contribute to fragmentation is a tradeoff that the local community or land manager will have to make.

by American Trails Staff


Overlook allows wildlife viewing without routing the trail through the habitat area at this Oregon wildlife refuge

Key Concepts

Typically as we go about building communities— and especially the infrastructure that supports them— we cut across and through streams and forests, windbreaks and prairies— the natural systems around us. This tends to leave ever-smaller areas that are even more directly impacted or influenced by humans.

This habitat fragmentation is considered by many biologists to be the single greatest threat to biological diversity. Some species, such as lynx and wolverine, for example, may not survive without large, unbroken blocks of habitat.

There is little specific knowledge of how much a trail may contribute to these factors or ultimately help degrade biological diversity. The extent of the impacts depends on a number of factors, including the type of habitat, the species present, and the characteristics of the trail, including how heavily it is used by people.

As mentioned above, trails have zones of influence (of variable width) associated with them. Taking this added width into account, it is easier to understand how a region crisscrossed with trails could end up with few areas not somehow influenced by humans.

In a complex series of interactions, fragmented habitats may see:

• an influx of plant and animal species (usually generalists) that like or tolerate the new conditions of light, wind,or human presence; and
• a decline of species that cannot tolerate these conditions or are adversely impacted by the species newly arriving in the trail’s zone of influence.

The new species may include weeds and other exotic plant species, as well as predators that eat the eggs or young of indigenous wildlife.

These new conditions and interactions can change the trail’s zone of influence in ways that may not be obvious to the casual observer.

The impacts of a trail on the biological diversity of a large area that has already been heavily disturbed may not be significant. For example, constructing a trail through a young, even-aged stand of lodgepole pine that has regrown after clearcutting may not change how wildlife use the area. If the stand has very low diversity of wildlife—as is often typical of this type of habitat—it is even possible wildlife diversity might increase with the creation of the trail.

Protecting large, undisturbed areas of wildlife habitat should be a priority. Deciding whether or not to build a trail that may contribute to fragmentation is a tradeoff that the local community or land manager will have to make.

Rules of Thumb

B.1 Big habitat areas.
When possible, leave untouched large, undisturbed areas of wildlife habitat. They are an important—and rapidly vanishing—resource. Identify and seek to protect all such areas when aligning a trail.

B.2 Edge trails.
It is better to route a trail around the edge of an area of high quality, undisturbed habitat, than through its center.

B.3 Trail density.
Keep the density of trails lower within and near pristine or other high quality areas to reduce the contribution of trails to fragmentation.

B.4 Stepping-stone patches.
Avoid small patches of high quality habitat in routing a trail. Such patches may be important stepping stones used by wildlife to move across the landscape.

B.5 Balancing needs across landscapes.
It is easier to balance competing wildlife and recreation needs across a landscape or region than it is on a specific trail project within a smaller area.

How to Extrapolate Practical Information From a Scientific Journal Article

There may be no existing specific studies of wildlife and the potential impacts of a trail for your particular area, but you can still get help from scientific journal articles and other sources. It may take time to get used to scientific jargon, but it is possible to cull practical information from such sources with patience.

In particular in reading an article, consider: Are the species of wildlife examined in the study the same as my project? Is the habitat type the same? Are the trail uses you anticipate similar to those studied, if any?

Through this process, you can start to develop new rules of thumb to apply to your trail project.

Further Reading

[Older publications may be available from libraries and used booksellers. Titles with links may still be in print, or are available in electronic format.]

Smith, “An Overview of Greenways” in Smith, D. and P. Hellmund, 1993. Ecology of Greenways. University of Minnesota Press, Minneapolis, Minn., pp. 2-4.
Forman, R. 1995. Land Mosaic: The Ecology of Landscapes and Regions. Cambridge University Press, Cambridge, pp. 405-434.
Noss, R. and A. Cooperrider, 1994. Saving Nature’s Legacy: Protecting and Restoring Biodiversity. Island Press, Washington, D.C., pp. 50-54.
Harris, L.D. 1984. The Fragmented Forest: Island Biogeography Theory and the Preservation of Biotic Diversity.