Wildlife corridors help animals move safely between separate patches of habitat. These connected areas of natural or restored land give animals a route through landscapes divided by roads, farms, cities, fences, and other human development. By connecting habitats that would otherwise be isolated, corridors can make it easier for animals to find food, mates, shelter, seasonal ranges, and places to raise their young.
Why animals need connected habitats
Wild animals rarely spend their entire lives in one small area. They may travel to find food, locate a mate, escape predators, reach water, establish a territory, or move between seasonal habitats. Some species also need to disperse when young animals leave the area where they were born.
Human development can interrupt these movements. A forest may be divided by a highway, for example, leaving animals with two patches of suitable habitat separated by a dangerous or unsuitable area. A growing city can create a similar barrier between wetlands, grasslands, or other natural areas.
When habitat becomes fragmented in this way, an animal may still have enough habitat to survive in one patch but have difficulty reaching other areas it needs. Roads can also increase the risk of collisions with vehicles, while fences and developed areas may prevent animals from moving normally across the landscape.
What a wildlife corridor is
A wildlife corridor is a relatively continuous route that allows animals to move between otherwise separated habitat areas. The corridor can be a strip of existing natural vegetation, a restored area, a river or stream environment, or a larger connected landscape.
Corridors do not all look alike. A narrow strip of forest might connect two woodland areas, while a much broader protected landscape could link large ecosystems. In some places, conservation planners maintain natural vegetation along rivers because these areas can provide both habitat and a route through developed landscapes.
A corridor does not necessarily mean that every animal will use the entire route. Different species have different requirements for food, cover, temperature, terrain, and space. A route that works well for one species may be unsuitable for another.
How corridors make movement safer
A corridor can provide animals with cover while they travel. Vegetation can give them places to hide from predators and reduce their exposure to open or heavily developed areas. Depending on its design and location, a corridor can also help animals avoid dangerous roads and other barriers.
Some corridors are designed around existing structures. For example, wildlife crossings can allow animals to pass over or under roads rather than crossing traffic directly. An overpass can be covered with soil and vegetation, while an underpass can provide a passage beneath a roadway.
These structures are most effective when they connect suitable habitat on both sides of the road and are designed for the animals expected to use them.
Corridors help animals find mates and maintain genetic diversity
Habitat connectivity is important not only for movement but also for reproduction. If animal populations become isolated, individuals may have fewer opportunities to encounter members of other populations.
Movement between populations allows animals to exchange genes. This can help maintain genetic diversity, which gives populations more variation on which natural selection can act and can reduce some of the risks associated with prolonged isolation.
The opposite can happen when habitat fragments remain separated for long periods. Small isolated populations may become more vulnerable to local environmental changes, disease, random population declines, and other pressures because animals cannot easily move in or out.
A corridor does not guarantee that populations will successfully interbreed, but it can make movement between them possible.
Corridors allow seasonal and long-distance movement
Some animals need to move between different habitats at different times of the year. Their requirements may change with temperature, food availability, water conditions, or reproduction.
For these species, a connected landscape can be especially important. A corridor may provide part of a route between breeding areas, feeding grounds, wintering areas, or other locations an animal regularly visits.
Long-distance movement also matters when animals expand into new areas. Young individuals leaving their birthplace may need connected habitat to disperse and establish themselves elsewhere. If human development blocks those movements, suitable habitat may remain effectively inaccessible.
Corridors can reduce the effects of habitat fragmentation
Habitat fragmentation does more than reduce the total amount of natural land. It can also divide remaining habitat into smaller, isolated pieces.
Two areas may contain enough habitat individually, yet animals may benefit greatly if those areas are connected. A corridor can therefore improve the functional connectivity of a landscape—the extent to which animals can actually move through it and use different habitat patches.
Connectivity is particularly important for animals that require large home ranges. A small isolated patch may not provide everything such an animal needs, but several connected areas can function as a larger usable landscape.
Corridors can be created or protected in many ways
Wildlife corridors do not always require creating completely new habitat. Protecting existing natural areas can preserve routes that animals already use. Conservation projects may also restore vegetation in gaps between habitat patches.
In agricultural landscapes, maintaining natural vegetation along waterways or between fields can provide routes through otherwise modified areas. In cities and suburbs, parks, green spaces, streams, and other connected natural areas can sometimes form movement pathways.
Where roads are unavoidable barriers, wildlife bridges, tunnels, fencing, and other measures can be combined. Fencing can direct animals toward a crossing instead of allowing them to enter the roadway, while the crossing provides a safer way through.
A corridor must work for the animals that use it
Simply drawing a line between two protected areas does not make an effective wildlife corridor. Animals respond to the actual conditions they encounter along the route.
A useful corridor needs appropriate habitat, enough space, and manageable levels of disturbance for the species involved. Its location also matters. A corridor that connects two forests but passes through unsuitable or highly dangerous terrain may provide little practical benefit.
Different animals can require very different corridor designs. A large mammal may need a broad, relatively undisturbed route, while a smaller species may use narrower vegetation corridors. Aquatic and semi-aquatic animals may depend on connected waterways and surrounding habitat.
For this reason, conservation planning often considers the behavior and habitat requirements of particular species rather than treating all wildlife as having the same movement needs.
Why connected landscapes matter as conditions change
Connectivity can also give animals more options when environmental conditions change. As temperature, rainfall, vegetation, and other conditions shift, some species may need to move toward areas that remain suitable.
A connected landscape can make such movement more feasible than a landscape divided into isolated habitat islands. Animals can potentially reach new areas instead of being confined to a single fragment.
This does not mean corridors solve every problem caused by environmental change. A corridor cannot replace sufficient habitat, eliminate threats such as disease or invasive species, or guarantee that a species can adapt. Its main benefit is maintaining the ability to move through the landscape.
Wildlife corridors connect more than patches of land
The central value of a wildlife corridor is that it turns separate pieces of habitat into a more connected landscape. Animals can move between areas that provide different resources, populations can remain less isolated, and species have greater opportunities to disperse and respond to changing conditions.
For wildlife living in increasingly fragmented landscapes, that ability to move can be as important as the habitat itself.
