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

The development and presence of roads can reduce landscape permeability, lead to habitat loss, and increase habitat fragmentation. It is these fundamental changes in landscape structure that can have both direct and indirect impacts on the conservation of species and biodiversity. In this review, I examine 215 research studies conducted between 2011 and 2015 that explore the impacts of roads and road networks on a wide range of species. I divided these studies into four main categories: 1) the direct effects of roads on wildlife, 2) the indirect effects of roads on wildlife, 3) the consequences of road networks on wildlife populations, and 4) survey design and mitigation including both innovations and evaluations. I found that the majority of studies (38%) explored the indirect effects of roads on wildlife, including displacement, fitness consequences, and road crossing ability of wildlife. Nevertheless, despite there being a pressing need to understand how existing road networks impact wildlife and how increasing road density may influence local and regional population persistence, only 10% of the studies considered the implications of road networks on wildlife. However, there is an increasing trend towards the development of predictive models that can be used for a better understanding of road network impacts, assess landscape connectivity, and devise mitigation. This review also highlighted the continued need to devise and evaluate mitigation measures so transportation authorities and conservation practitioners may be better equipped to address the ecological implications of roads and proposed road development.