Toward Understanding the Ecological Impact of Transportation Corridors

Bennett, Victoria J.; Smith, Winston P.; Betts, Matthew G. 2011. Toward understanding the ecological impact of transportation corridors. Gen. Tech. Rep. PNW-GTR-846. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 40 p. Transportation corridors (notably roads) affect wildlife habitat, populations, and entire ecosystems. Considerable effort has been expended to quantify direct effects of roads on wildlife populations and ecological communities and processes. Much less effort has been expended toward quantifying indirect effects. In this report, we provide a comprehensive review of road/transportation corridor ecology; in particular, how this new field of ecology has advanced worldwide. Further, we discuss how research thus far has shaped our understanding and views of the ecological implications of transportation infrastructures, and, in turn, how this has led to the current guidance, policies, and management options. We learned that the impacts of transportation infrastructures are a global issue, with the potential to affect a wide variety of taxonomically diverse species and ecosystems. Because the majority of research to date has focused on the direct and more aesthetic and anthropocentric implications of transportation corridors, mainly wildlife-vehicle collisions, it is a fairly standard practice to incorporate underpasses, green bridges (i.e., overpasses), fencing, and barriers into road corridors to alleviate such impacts. Few studies, however, have been able to demonstrate the efficiency of these structures. Furthermore, it is becoming increasingly evident that the indirect implications of transportation infrastructures (i.e., behavioral responses of wildlife individuals to roads) may be more pervasive, at least from the standpoint of biological diversity. Understanding how road corridors influence the functional connectivity of landscapes is crucial if we are to effectively manage species of concern. With these issues in mind, we propose a program of study that addresses the indirect and cumulative implications of transportation infrastructure on species distributions, community structure and ecosystem function.