A wildlife corridor is a route or strip of land, water or air that connects separated habitats and allows wildlife to move between them. Such routes can be natural or artificial, and they can span any distance, from a few meters to many miles or even between continents.
Some wildlife corridors are the long-established seasonal migration routes of land animals, fish and birds. The knowledge of these routes is often passed down between generations and they are typically used consistently year after year. In addition to being important pathways for movement, they can also provide critical seasonal resources that allow the migrating animals to rest and feed there.
Wildlife corridors are crucial not only for some animals but also for some plants. They can facilitate plants' colonization, migration and interbreeding by various means, including through the spreading of seeds by wind, water, gravity and explosive seed pods. Seeds are also spread by animals by excreting them after eating fruit, by attachment to their fur with burrs, and by burying them. They can also be spread by ants and other insects.
Wildlife corridors have been increasingly damaged or destroyed by human activity that makes movement between the fragmented habitats difficult or impossible, including road building, dam construction, logging, agriculture, urbanization, fence building and the draining of wetlands. This has been having severe effects on numerous species, including reducing their populations and leading to extinctions.
The construction of artificial wildlife corridors has recently come into prominence in response to the increasing fragmentation of natural habitats and a growing understanding of the importance of such corridors. In addition to reconnecting natural, seasonal migration routes, they can increase the size of the area available for some apex predators that require large territories. They also facilitate an exchange of individuals between what would otherwise be isolated populations, thus helping prevent inbreeding and the consequent reduction in genetic diversity. Moreover, they can facilitate the re-establishment of populations that have been diminished or eliminated as a result of natural events such as disease, fires or floods.
Artificial wildlife corridors can take various, diverse forms and sizes, according to the species for which they are intended and the physical and other characteristics of the area in which they are to be constructed. In addition to merely serving as a route for travel, they can also provide cover and food for some species as well as increase the total habitat size. Examples of common local wildlife corridors include hedges or rows of trees between woodlands, wooded areas along streams, and underpasses and bridges under or over roads.