Corridors created by humans are typically associated with roads, that are major sources of habitat fragmentation. Wildlife overpasses or underpasses are key examples of human-created corridors. Other corridors through urban areas such as greenways or riparian buffers may also constitute man-made corridors.
Man-made corridor examples
The U.S. Highway 93 North (US 93 North) – ‘The People’s Way’ – reconstruction project represents the most extensive wildlife-sensitive highway design effort in the United States to date. This project is within northwest Montana on the Flathead Indian Reservation, the homeland of the Confederated Salish and Kootenai Tribes (CSKT). To mitigate the expansion of this 56-mile long road section on the ecological and cultural integrity of the Reservation, the Montana Department of Transportation built 41 fish and wildlife crossing structures, 16 miles of wildlife fencing, 39 jump-outs, and many wildlife crossing guards.
ARC is an interdisciplinary group thinking about new ways to build and construct wildlife crossing structures. Roadways are major sources of fragmentation that disconnect landscapes. They are also a major source of animal mortality and of vehicle accidents. New designs that facilitate road crossing by animals can have benefits for wildlife and for people.
Wildlife and Roads is a consortium dedicated to providing instructions for road creation to protect wildlife and reduce vehicle collisions. In addition to providing resources, their website has numerous examples of wildlife crossings.
The TransCanada Highway cuts across Banff National Park in Alberta, Canada, fragmenting critical habitat and creating a large barrier to movement for wildlife. To facilitate individual movement, especially of large, wide-ranging species swidth=”"ch as grizzly bears, wolverines, and elk, man-made overpasses and underpasses were constructed to span the highway and funnel individuals from one side to the other. While some species take a long time to begin using these structures, they ultimately provide a critical connection between fragmented forests and allow for continued gene flow between populations. In addition, road closures and the removal of man-made structures have allowed natural corridors to re-emerge within the region.
The Netherlands contains over 600 man-made corridors, including overpasses and underpasses along busy highways. The longest of these, the Natuurbrug Zanderij Crailo, is an overpass that is 50 m wide and over 800 m long. It was completed in 2006, and spans a railway line, business park, river, roadway, and sports complex. This corridor is part of larger protected area within the country, the Veluwe, which consists of 1,000 square kilometers of forest and other natural habitats. Species known to use these corridors include roe deer, red deer, wild boar, and the endangered European badger.