For all ecological effects, references are organized by the scale of the study. Three scales were used: single segment, intermediate—political/ecological, and national. Single segment refers to studies that examine the impacts of a single road on an ecosystem. In this case, several roads may be involved in the study; however, the results do not address the cumulative effects of these roads. For example, the effect of road pollution on insect populations living adjacent to a road, or the barrier effect of a road on a species' movement would be classified as “single segment.” Intermediate scale studies examine the cumulative effect of roads on a region. In other words, the combined effect of more than one road determines the results of the study. For example, the effect of several roads on one lake, range expansion by using roads as a dispersal corridor, or genetic isolation of a population surrounded by more than one road would be classified as intermediate. The boundary of a region is either politically (e.g., state of Florida, national park) or ecologically determined (e.g., a watershed, an animal’s home range). National scale studies are very rare and they cover the effects of roads over an entire country.

The format for the bibliography is as follows:

Sample Section

Summary of Ecological Effects

A paragraph is written here explaining the ecological effects for the section. Ecological effects are italicized in paragraph.

Ecological effect:


a. Single segment

  • Reference 1

  • Reference 2

  • Etc.

b. Intermediate—-political/ecological

  • Reference 1

  • Reference 2

  • Etc.

c. National

  • Reference 1



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