Evaluating the effectiveness of road mitigation measures

Abstract

The last 20 years have seen a dramatic increase in efforts to mitigate the negative effects of roads and traffic on wildlife, including fencing to prevent wildlifevehicle collisions and wildlife crossing structures to facilitate landscape connectivity. While not necessarily explicitly articulated, the fundamental drivers behind road mitigation are human safety, animal welfare, and/or wildlife conservation. Concomitant with the increased effort to mitigate has been a focus on evaluating road mitigation. So far, research has mainly focussed on assessing the use of wildlife crossing structures, demonstrating that a broad range of species use them. However, this research has done little to address the question of the effectiveness of crossing structures, because use of a wildlife crossing structure does not necessarily equate to its effectiveness. 425-448 DOI 10.1007/s10531-012-0421-0 examining the effectiveness of crossing structures is exacerbated by the fact that such studies are often poorly designed, which limits the level of inference that can be made. Without well performed evaluations of the effectiveness of road mitigation measures, we may endanger the viability of wildlife populations and inefficiently use financial resources by installing structures that are not as effective as we think they are. In this paper we outline the essential elements of a good experimental design for such assessments and prioritize the parameters to be measured. The framework we propose will facilitate collaboration between road agencies and scientists to undertake research programs that fully evaluate effectiveness of road mitigation measures. We discuss the added value of road mitigation evaluations for policy makers and transportation agencies and provide recommendations on how to incorporate such evaluations in road planning practices.

Wild vertebrates roadkill aggregations on the BR-050 highway, state of Minas Gerais, Brazil

“…The adequate location of wildlife crossings, for example, can improve or maintain connectivity between animal populations (LESBARRÈRES; FAHRIG, 2012; VAN DER GRIFT et al, 2013). Significant roadkill hostspots found for vertebrates, mammals, and for some species indicate that mortality is concentrate on some segments of the road and, therefore, certain areas are better than others to implement mitigation measures (Coelho et al, 2008).…”

“…A higher intensity of roadkill aggregations on the highway searched was observed in the stretch between km 18 to 24, suggesting that this area should be prioritized in the adoption of possible mitigation measures. The construction of wildlife crossings in conjugation with fencing to direct animals and prevent them from crossing the highway is recommended (BAGER, 2003;GLISTA et al, 2009;GRILO et al, 2010;VAN DER GRIFT et al, 2013). This technique brings the great advantage of preventing roadkill and ensuring the maintenance of gene flow between animal populations, however this is very expensive (GLISTA et al, 2009;GRILO et al, 2010; VAN DER GRIFT et al, 2013) and its application in a road that already exists is difficult.…”

“…In this context, the detection of aggregation areas (hotspots), through analyses, using geographic positioning of roadkill, makes it possible to know where to install the targeted mitigation measures, such as warning signs, electronic barriers, speed bumps, olfactory repellent, light and sound, fencing and wildlife crossings (GLISTA et al, 2009;GRILO et al, 2010; VAN DER GRIFT et al, 2013). Since it is not financially viable for most governments develop strategies that mitigate roadkill along the total length of all roads (GOMES et al, 2008), road managers need reliable data to identify when and where certain species are susceptible to high roadkill rates in order to implement mitigation measures at these sites ).…”

Effects of Road Density and Pattern on the Conservation of Species and Biodiversity

“…For example, four studies postulated that the way crossing structures are currently selected and even evaluated is biased and called for more effective mitigation selection and surveillance protocols [104,[125][126][127]. Similarly, a study conducted in a conservation area in South Africa revealed that the way roadkill surveys are undertaken can strongly influence road mortality estimates [128].…”

Changes in behavioural responses to infrastructure affect local and regional connectivity – a simulation study on pond breeding amphibians

“…Once mitigation measures are implemented, efforts are seldom put into discovering how well they work (Lesbarreres and Fahrig 2012;van der Grift et al 2013). Simulation studies like the one presented here can provide a means to assess the effects of planned road designs and mitigation measures (van der Ree et al 2009).…”