Effects of roads and traffic on animal abundance

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Over the past 100 years roads have become a dominant landscape feature and this infrastructure continues to expand. Recently, ecological researchers and transportation planners have become increasingly concerned about the potential effects of roads and traffic on animal populations. Is this concern justified? How strong is the evidence that roads have a large impact on the distribution and abundance of animals? Although many studies have been conducted, almost all of them suffer from limitations in study design, which means it is not possible to estimate the effects of roads separately from the effects of other landscape changes such as deforestation, wetland loss, or agricultural intensification. My first objective is to rectify this situation; I will conduct empirical studies to determine the impact of roads and traffic on animal populations, independent of and in comparison to other landscape changes. Given that roads affect animal abundance, an important question for mitigation of these effects is, what kinds of species are most strongly affected by roads and how are they affected? For example, fencing and wildlife crossings can reduce road effects on species that are affected mainly through traffic mortality, while effects of traffic disturbance on animal abundance can likely only be mitigated by reducing traffic density in the landscape. I develop a set of hypotheses and predictions of how species characteristics - their movement ranges, reproductive rates, natural densities (territory/home range sizes), trophic interactions, and behavioural responses to roads, traffic emissions, and individual vehicles - determine the direction and size of the impact of roads on animal populations. My second objective is then to conduct a set of studies to test these predictions. The proposed research addresses three important applied questions: (i) to what extent should environmental and transportation agencies be concerned about the impacts of roads and traffic on wildlife? (ii) what kinds of species should be monitored for potential effects of roads? and (iii) what will be the most effective mitigation measures to minimize these effects?