In the 1950s, President Eisenhower led the creation of a national system of interstate highways across the United States. Though the system was originally conceived as a necessary part of defending the country, today it is the primary basis of our nation’s commerce and travel. Until recently, little thought was devoted to the implications of building roads through wildlife migration corridors.

These corridors – the paths that wildlife follow to access seasonal resources such as various foods, water and mating opportunities – ensure the persistence of a wide range of migratory animals across the globe. As society expands its reach and wild places are increasingly targeted for development, centuries-old corridors have been disrupted and habitat compromised.

During most of the 20th century, new road building decisions focused on issues like terrain, soil, and other location considerations, along with logistics and cost. It was not until late in the twentieth century that projects started to consider the needs of wildlife in relation to road construction and maintenance. As a result, many roadways pass through what were once the best habitats, for example along rivers.