Wildlife And Trails Primer - Part G. A Site’s Existing Impacts

Planning Trails with Wildlife in Mind

Assessing the amount of human disturbance already along a potential trail alignment can help set more real- istic wildlife goals for a trail project. Trail alignments may pass through one or more of the general levels of modification along a gradient from urban to pristine.

by American Trails Staff


Sand Creek trail corridor includes wetlands and flowing water but it is also a highly industrialized area

It is very rare that an area proposed for a trail hasn’t already seen at least some impact from humans. The questions then become

  • How disturbed is the site?
  • What kinds of impacts to wildlife already exist there?

Key Concepts

With this kind of ecological evaluation, it will be easier to set reasonable wildlife goals for a trail or to evaluate the tradeoffs between wildlife and trails. Every trail project should have wildlife goals. The specific wildlife goals and rules of thumb you apply will partly depend on how disturbed a site is.

Typically, urban landscapes are heavily disturbed and restoring habitat may be the principal wildlife goal. In more pristine settings, preserving what is already there and minimizing impact may be the major concerns.

An important first step is determining where a site fits on the gradient of human modification ranging from urban (highly modified) to pristine (few modifications).

Even portions of wilderness areas may have had some human impacts from activities such as mining, forestry, or road building. Understanding these modifications can help guide trail alignments. For example, trails might follow ecological edges created by historic roads or timber cuts.

In gauging how modified an area already is, there are some practical questions to ask:

• Generally, what kind of wildlife habitat is present? What condition is it in?

• Are the plants and animals typically associated with that habitat actually present? Is the ecosystem already impoverished to some extent?

• What are and have been the human impacts to wildlife in the area?

• What are the surrounding land uses and condition of habitat? How close is any nearby develop- ment? Are there already roads bounding the area under consideration for a trail, posing obstacles to wildlife movement?

• Overall, to what extent is the site insulated from external forces?

• What opportunities are there to improve habitat on the site?

Rules of Thumb

G.1 Patterns of disturbance.
The best trail alignments work with the existing patterns of disturbance already in a landscape, rather than imposing an entirely new set.

G.3 Urban limitations.
In urban landscapes there are often few options for routing trails other than streetside (where there are not many ecological implications) and along streams and other drainages often already transformed for flood control.

G.4 Restoring habitat. Trail projects can aid wildlife by being catalysts for restoring habitat, creating wetlands, and planting native plant species for food, cover, and visual screening.

G.5 Seeking professional help.
Without special training, it’s easy to overlook or oversimplify wildlife issues. Get professional assistance whenever possible.

Further Reading

[Older publications may be available from libraries and used booksellers. Titles with links may still be in print.]

Thorne, “Landscape Ecology,” in D. Smith and P. Hellmund, 1993. Ecology of Greenways. University of Minnesota Press, Minneapolis, Minn., p. 27.

Forman R. and M. Godron, 1986. Landscape Ecology. John Wiley and Sons, New York, pp. 286-310.