This is the third and final post in a series looking at wildlife movement, corridors and roads. Read the first post, Ecology Lesson: Population Movements, which was followed by Corridor Ecology and Planning.
Roads traverse all terrain
Roads crisscross the entire country covering much of the land. Highways take us through states or across the whole country, streets cover cities and dirt roads link rural areas to cities. They traverse over rivers, lakes, mountains, valleys, deserts and forests. Some highways are many lanes wide and some bridges are modern engineering marvels. They bring us commercial goods, foods and fuel across great distances. There are over 4 million miles of roads in the United States alone.
Road ecology is a field that addresses the relationship between roads, wildlife and the environment. The topic has received a lot of attention over the past 30 years with a lot of focus on roads and wildlife. Germany and Switzerland were two of the earlier countries to look at modifying the current infrastructure to address problems, and amphibians in Western Europe were some of the earliest beneficiaries of wildlife tunnels.
Because roads cover such vast terrain, they are subjected to the many environmental conditions those regions produce such as mudslides, ice storms, windy debris and the shifting earth. They also, in turn, greatly influence environmental conditions by creating impervious surfaces for rain, influencing the vegetation structure adjacent to them, they cause erosion where they’ve cut into hills, and when crossing over a stream, they funnel the water through a culvert. Throw bridges, pipes, overpasses and noise barriers into the mix and it’s a complicated system of man-made structures and the natural environment.
The vegetated edge of roads are often mowed or sprayed with pesticides which creates a hard edge to the adjacent habitat and a severe barrier. This disturbed area creates a zone for plant opportunists and many invasive plants such as blackberry do well there and once established, have a nice road to spread along. The roadsides, which have heavily maintained vegetation also create a different habitat for wildlife. Most everyone can recall seeing raptors sitting alongside roads surveying the short vegetation for rodents. Other species that find this type of habitat beneficial are reptiles, butterflies, amphibians and bees. If the roadside is managed for biodiversity, it could become an effective habitat. Designing successful roadside habitat is possible if different, conflicting goals can be achieved such as visibility for both wildlife and drivers, cover and a way to cross the road safely. There’s an excellent digram in chapter 4 of the very worthwhile book, Road Ecology: Science And Solutions, that illustrates the various patterns of roadside vegetation. Continue reading »