Wildlife corridors are designed to help limit the impacts of human infrastructure on animals. These impacts can look like increased fragmentation of habitat areas for animals, the development of dense urban areas, busy freeways or other roads, building dams, and other things. An estimated 1 to 2 million cars hit animals every year—and that number only includes reported instances of collisions, so it’s likely the number is even higher. This indicates that there are strong social (and economic) reasons to implement wildlife corridors: people generally only report hitting large animals or when the collision creates a disabled vehicle.
Wildlife corridors can take many forms, including underpasses, gaps in guard rails, bridges, and connected habitat corridors (i.e. – riparian areas for migratory animals) that are designed specifically to allow species to move (more) safely across roads and other barricades—which can include large swathes of developed areas.
I was reminded of the significant impact wildlife corridors can have on animal welfare recently, while reading about one of the Santa Monica mountain lions (P-39; Puma concolor), a young female lion, who was killed while crossing a highway in the Santa Monica mountains. Her young cubs were orphaned as a result, and according to the National Park Service, are not expected to live.
P-22, the mountain lion which has made Griffith Park (home of the Hollywood sign) his home managed to safely cross two freeways and through a densely populated urban area to reach the park which is only 8 square miles (he could use up to 200 square miles as his territory, if that was an option). But, in this isolated area, he is unlikely to find a mate and he is subject to exposure to rodenticide, as well as other pollutants.
Wildlife corridors not only provide a way for animals to move from one place to another more safely—it can also be a way of creating enough territory that a species of animal can just survive. One example of this is the Terai Arc Landscape, which traverses 14 different protected areas in India and Nepal. The protected areas are comprised of grasslands, forests, and river valleys, and as such offer critical habitats to a number of species including Indian rhinos (Rhinoceros unicornis), Asian elephants (Elephas maximus), and Bengal tigers (Panthera tigris), all of which are considered vulnerable or endangered. Individually, the parks and preserves don’t offer enough acreage to support these species, but connected they provide plenty of habitat range.
Other examples of wildlife corridors include overpasses off Highway 9 in Colorado that allow elk to migrate; a bridge structure in Australia that allows crabs to scuttle up and over a road during their migratory season, turtle underpasses in Florida, and Norway’s bee highway. Design—and purpose—of these corridors matter, and the type of animal(s) and their preferences or needs around habitat must be considered when creating wildlife corridors.
Wildlife corridors are not currently a standard part of restoration projects in a traditional sense—but restoring or enhancing habitats, and strategically planning to preserve or build around specific flyways or migratory pathways can serve many of the same purposes. These things allow for the less habitat fragmentation and less obstructed movement of wildlife. Restoration efforts can also enhance critical habitat areas (i.e. – resting, breeding, or nesting spots) and decrease the influence of human development (i.e. road noise, river sedimentation due to increased runoff).
Restoration professionals, science educators, conservationists, departments of transportation and others can all help clients and the public better understand the benefits of wildlife corridors—not only for wildlife, but for people as well.