Road Ecology Center

Improving ecological conditions around the road network is emerging as a significant objective of transportation, along with providing safe and efficient mobility. Reading landscape patterns is a key to success. The prime goal of this article is to identify ecologically appropriate and inappropriate locations for road construction, removal, and mitigation in the network. Other goals include understanding the effect of road location between two large natural patches, and progress in developing an ecologically optimum network form. Simple spatial models are used with three independent variables: (1) road size or connection, (2) road location relative to natural patch or corridor, and (3) size/width of patch or corridor. Dependent variables are habitat loss, degradation, and fragmentation. Modeling results suggest that in a landscape of dispersed natural patches and corridors, by far the greatest road effect (ecological impact) results from a highway that bisects or highway network that subdivides a large natural patch. Overall, effects are greatest where a road crosses or is alongside large patches and wide corridors. For both types, the least effect is where a small road is alongside the margin. Road effects are relatively low around narrow corridors and lowest around small patches. Model results indicate that the probability of species crossing between two large natural patches is lowest where a highway slices across near the midpoint. A highway network has a greater effect on habitat conditions in a natural landscape than in an agricultural or suburban landscape. Habitat degradation appears to have a greater ecological effect than does habitat loss or fragmentation in the landscape. An ecologically optimum road network contains: a few large roadless areas; a few busy roads rather than many lightly used roads; and perforated roads (for species movement) between the large roadless areas. In conclusion, a simple patch-corridor analysis of a landscape points to clear solutions for locating road construction, removal, and mitigation to maximize ecological benefits. The two overarching principles are minimizing roads in and around large natural patches and maximizing effective habitat connectivity between the large natural patches.