Leaf Litter

In this Issue

We look into the direct and indirect impacts that roadways have on wildlife.

By Keith Bowers

Article Index

With the stones we cast at them, geniuses build new roads with them. –Paul Eldridge 

Thanks to the Interstate highway system, it is now possible to travel across the country from coast to coast without seeing anything. –Charles Kuralt

Like it or not, roads have become the arteries of our social and economic lives. Roads are necessary to transport goods and services to the marketplace, move people to and from their places of work, shopping, and social engagements, and serve as vital links to public health, safety and welfare. Roads in the U.S. cover about 1% of the land area, an area equivalent to the state of South Carolina. It is estimated, however, that 20% of U.S. land area is directly affected ecologically by the road system. But in our quest to build roads to serve our burgeoning needs, biodiversity — that is the total diversity and variability of living things and the systems of which they are a part of — seems to have been left by the roadside. Like them or not, roads have a far reaching impact on biodiversity, both in terms of new construction and ongoing operations.

Typically when we think about roads and wildlife, the first thing that comes to mind is direct impacts to wildlife – road kill. It is estimated that in the U.S. approximately 1 million mammals are killed on roadways annually.  If we consider insects, amphibians, birds and a host of other taxa, we are most likely looking at billions of species each year. In the United Kingdom, it is estimated that millions of birds and 20-40% of UK’s breeding population of amphibians are believed to die each year on roads. Even the mere presence of a road can impact wildlife species. Dutch research for example, showed that out of 12 bird species examined, 7 exhibited reduced densities near roads than in similar habitats away from roads.  Roads are also responsible for changes in plant species composition, plant performance and soil nutrient levels along their right-of-ways.

While direct impacts are important to consider, it is the indirect impact that may have the biggest effect on terrestrial, aquatic and avian species. Fragmentation of habitat (link to our past Leaf Litter issue on fragmentation), water runoff pollution, air pollution, noise and artificial light pollution, along with the effects of spillages, litter and roadside management practices can all erode the quality of biodiversity and ecological integrity of the landscape.

While almost any form of road development will have some negative effect on the environment, there are many promising initiatives taking place throughout the world to reverse this trend. Many European countries are taking bold steps to initiate biodiversity action plans that address methods to reduce and mitigate road impacts on wildlife. These initiatives range from broad policy goals to preserve habitat connectivity (see Guiding Principles for Conducting Biodiversity Assessments for Road Projects (UK) provide link) by promoting mass transportation projects and better land use planning, to specific mitigation techniques to allow wildlife movement across roads.  Many U.S. transportation agencies are also beginning to incorporate both wildlife avoidance and mitigation strategies in road design.

In this issue of Leaf Litter, we highlight measures to protect, restore and mitigate wildlife habitat in relation to roads. We also interviewed Bethanie Walder, Executive Director of the Widllands CPR. Wildlands CPR is becoming one of the leading authorities and sources of information on the ecological effects of roads and off-road vehicles. Bethanie talks about some of the strategies being used to mitigate and restore ecosystems impacted by roads. Our Leaf Litter Survey on roads and their impacts to wildlife brought in some interesting comments, provocative thoughts and probing questions. Be sure to check it out. Finally, we have packed this issue of Leaf Litter with plenty of resources, information and links for you to take action. Remember:

He who walks in the middle of the road gets hit from both sides. -George Schultz

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