A road to conservation: understanding the dynamics of road-effects and road-effect mitigation

Abstract

Globally, roads are one of the most ubiquitous forms of human infrastructure, and have been identified as a serious conservation concern. Though roads impact wildlife in a variety of ways, their effects are often negative. Perhaps the most concerning threats are habitat fragmentation and mortality via wildlife-vehicle collisions. Attempts to manage the negative effects of roads have had mixed results, and major gaps in our understanding of how roads affect wildlife populations and the effectiveness of strategies to mitigate road-effects remain. Many factors contribute to these gaps, particularly the logistical constraints associated with road-effect monitoring and weak study designs that inhibit strong inferences crucial for effective management. To this end, I approached road-effect mitigation in a holistic way. First, I documented and analyzed the local-scale population and spatial ecologies of large mammals around a newly twinned highway. I found that highway twinning, a common strategy to accommodate increased traffic volume, had little effect on large mammals. Second, I focused on the optimization and evaluation of road-effect mitigation (i.e., exclusion fencing and roadcrossing structures). I developed a procedure for identifying ideal locations for mitigation features by comparing road monitoring data to landscape resistance models for both large mammals and herpetofauna. Using this approach, I designed a mitigation plan for reptiles and amphibians, which I evaluated using a robust 6-year Before-After-Control-Impact design that included road surveys, trapping, and two methods of monitoring tunnel usage: trail cameras and PIT tag scanners. I found that exclusion fencing was effective for turtles and amphibians but had no impact on the number of snakes detected on the road. Crossing tunnels were well used by reptiles and amphibians and I demonstrated that for turtles, tunnels effectively facilitated connectivity at the population-level. Finally, I investigated the value of outreach as a long-term conservation strategy in the context of road ecology. I demonstrated that outreach programs significantly increase the perceptions of youth concerning their own likelihood to participate in conservation. Further, using a mixed-methods approach, I identified the aspects of outreach that were most effective at eliciting this change, creating broadly applicable guidelines to optimize future outreach endeavors. By addressing knowledge gaps pertaining to each phase of road-effect mitigation, I have provided a structural framework from which the field of road ecology can continue to flourish. My findings have serious implications for wildlife management and conservation because they increase our understanding of road-effects and importantly, how to increase the success of road-effect mitigation.