THE ECOLOGY OF RURAL ROADS: EFFECTS, MANAGEMENT, AND RESEARCH

Road networks form the basic transportation system for most of the world’s inhabitants, stimulating local and regional economies. Scientific advances in recent years have revealed that this vast, growing, planetary construction boom has been occurring mostly in non-urban environments, and most aggressively in developing frontiers of tropical regions. However, even in highly urbanized countries, road networks consist mostly of roads outside of urban areas. To produce a reliable, comprehensive picture of the global road network, scientists have taken advantage of improvements in mapping technologies, including automated detection from satellite imagery and real-time mapping on the ground. Because the extent of the global road network is increasing at a rapid, unprecedented pace, the pervasive and sometimes dramatic impacts on ecosystems and their services in rural areas will continue. The science of road ecology has emerged to quantify these effects and propose solutions to mitigate the detrimental effects of roads and their traffic. This report explains these effects and examines implications of road ecology research for decisions and actions, including some management practices to help mitigate the negative ecological effects of rural roads. Some of the major ecological effects of roads in rural landscapes include: • Destruction of habitat, including fragmentation of plant and animal populations. • Traffic disturbance, including animal-vehicle collisions that reduce populations and/or habitat quality to the point of causing local extinctions. • Introduction and establishment of invasive and non-native plants and animals that compete with native flora and fauna. • Pollutants, including hydrocarbons, salts, nitrates, heavy metals, and pesticides, emitted from vehicles, road surface materials, and associated with dust. These pollutants persist in and change the roadside environment, including aquatic habitats (e.g., near-road streams) and downstream aquatic systems (e.g., estuaries). • Alteration of hydrology: ditches change water movement and infiltration patterns; road structures affect erosion and sedimentation of streambeds; culverts fragment streams altering movement of aquatic fauna. • Increased access to remote places that, in turn, enables the collateral destruction of habitats, the degradation of ecosystems, and the loss of biodiversity. Several strategies exist for mitigating the negative effects of roads in rural landscapes. Road ecology can be applied advantageously in transportation policy, planning, and decision making to reduce the impacts of roads by evaluating development alternatives, including whether to build a road, where to build, as well as how and when to build. Such strategies can be applied at continental, regional, or local scales, contributing to the discussion of tradeoffs within a framework of sustainable development. Strategies for mitigating environmental impacts include configuring roads to avoid destroying ecosystems, installing fences to reduce road mortality, creating safe passages for wildlife under and over roads, controlling traffic during critical times for key species, and following best practices for road construction and maintenance. Road ecology is a young science that has advanced rapidly in recent years. Thousands of scientific studies have, since the late 1990s, measured various environmental responses to roads and their traffic with the intention of quantifying the extent and magnitude of ecological effects. But, the current challenges to road ecology now involve working with large volumes of data, integrating datasets, and incorporating these data into models. Furthermore, there is a challenge in synthesizing the information across disciplines, for example, combining data on hydrological, chemical, and health effects to understand the depth and range of ecological responses. Therefore, as road ecology matures and addresses these challenges, a much more nuanced and complete understanding of the ecological effects of roads is emerging. Smaller low-volume rural road systems are not usually as well-mapped or as well-studied as their higher-volume counterparts, yet they constitute the lion’s share of the global road network and are at the frontiers where ecological patterns and dynamics strongly influence human activities. Conversely, the characteristics of the road network in these far-flung locations (e.g., how well connected they are) have implications for the future of rural communities and the landscapes in which they are embedded. While these roads offer many benefits to people living in remote rural areas, grappling with rural road impacts and addressing them with solutions for mitigating their negative ecological effects is a priority for road ecology. The community of road ecology scientists is, in cooperation with land managers and decision makers, committed to identifying the problems and evaluating potential solutions to better manage road-related ecological impacts in rural landscapes.