Wildlife mitigation strategies such as wildlife crossing structures and associated fencing are highly effective at reducing wildlife-vehicle collisions (WVCs) and facilitating wildlife movement across roads. However, while WVCs and landscape fragmentation are pervasive for road networks, installing adequate mitigation measures is often considered by transportation agencies to be prohibitively expensive. Understanding where WVCs occur most frequently, where important areas for wildlife movement exists, where roads may pose barriers to wildlife movement, and where mitigation will be cost-effective, is therefore essential for effective transportation planning and efficient allocation of public and private resources.
We conducted a west-wide assessment of WVC hotspots and ecological connectivity that pinpoints opportunities for cost-effective highway mitigation across eleven states. We provide a regional analysis evaluating three key factors that inform transportation decision-making to invest in highway mitigation measures that reduce WVCs and improve habitat connectivity – safety, connectivity, and the economic cost-benefits of the mitigation measures deployed. Similar studies identifying and prioritizing locations for mitigation rarely examine these factors together. This study identifies the most important road segments where each of these three factors are most significant and where high value locations for the three factors converge, across the West and within each state individually.
Using public data on WVCs from the eleven western states, we identified and mapped WVC hotspots and utilized cost-benefit analysis methods with updated economic values from 2022 to identify road segments where the benefits of implementing mitigation significantly outweigh the monetary costs incurred by WVCs over time. We also calculated ecological connectivity based on the degree of naturalness using a gradient-based approach and identified locations where wildlife movement and habitat connectivity should be increased through highway mitigation. Further, we identified the nexus between high WVCs, high landscape connectivity, and existing conservation investments (protected and conserved lands) and regulatory requirements (i.e., designated critical habitat for threatened and endangered species). We also examined how traffic volume may influence connectivity. Perhaps most importantly, we created an interactive online map allowing a user to examine combinations of data layers at the scale of their choosing. This exemplifies the 2023 ICOET theme “Partnering for a Healthy Landscape,” as we strove to provide the ability for a range of professionals to use results across many jurisdictions and boundaries.
The project seeks to support decision-makers and partners with the best available sites in each of eleven western states to invest their limited dollars for highway mitigation to improve wildlife movement and habitat connectivity and reduce dangerous and costly WVCs. Project results have the potential to influence and support transportation policy and planning and increase the pace and scale of mitigation.