How Effective Is Road Mitigation at Reducing Road-Kill? A Meta-Analysis

By T. Rytwinski, Kylie Soanes, Jochen A. G. Jaeger, L. Fahrig, S. Findlay, J. Houlahan, R. Ree, E. A. Grift. PLoS ONE, 2016

296 citations recorded by the source corpus.

Road traffic kills hundreds of millions of animals every year, posing a critical threat to the populations of many species. To address this problem there are more than forty types of road mitigation measures available that aim to reduce wildlife mortality on roads (road-kill). For road planners, deciding on what mitigation method to use has been problematic because there is little good information about the relative effectiveness of these measures in reducing road-kill, and the costs of these measures vary greatly. We conducted a meta-analysis using data from 50 studies that quantified the relationship between road-kill and a mitigation measure designed to reduce road-kill. Overall, mitigation measures reduce road-kill by 40% compared to controls. Fences, with or without crossing structures, reduce road-kill by 54%. We found no detectable effect on road-kill of crossing structures without fencing. We found that comparatively expensive mitigation measures reduce large mammal road-kill much more than inexpensive measures. For example, the combination of fencing and crossing structures led to an 83% reduction in road-kill of large mammals, compared to a 57% reduction for animal detection systems, and only a 1% for wildlife reflectors. We suggest that inexpensive measures such as reflectors should not be used until and unless their effectiveness is tested using a high-quality experimental approach. Our meta-analysis also highlights the fact that there are insufficient data to answer many of the most pressing questions that road planners ask about the effectiveness of road mitigation measures, such as whether other less common mitigation measures (e.g., measures to reduce traffic volume and/or speed) reduce road mortality, or to what extent the attributes of crossing structures and fences influence their effectiveness. To improve evaluations of mitigation effectiveness, studies should incorporate data collection before the mitigation is applied, and we recommend a minimum study duration of four years for Before-After, and a minimum of either four years or four sites for Before-After-Control-Impact designs.

Subfields: Ecology

View Paper: https://www.semanticscholar.org/paper/78ed048444ce41177c9c9e044d77212229356047

Citations in the corpus

• The value of monitoring wildlife roadkill (2020, unknown): “…exist in the field of road ecology as a whole (Forman and Alexander 1998; Coffin 2007), the use of citizen science in monitoring wildlife roadkill (Shilling et al. 2015; Vercayie and Herremans 2015), and the use and effectiveness of mitigation strategies (Grilo et al. 2010; Rytwinski et al. 2016).”
• The challenges and opportunities of coexisting with wild ungulates in the human-dominated landscapes of Europe's Anthropocene (2019, unknown): “Many mitigation measures have been tested, but few have been consistently documented to effectively reduce collision frequency apart from fencing longer road sections in combination with wildlife crossing structures (Huijser et al., 2016; Rytwinski et al., 2016).”