Animals need room to roam; one way to provide it is to link up natural spaces using 'wildlife corridors'
I stood on a ridge top looking over an ocean of trees - the largest area of nearly unbroken hardwood forest in the central American Midwest. To get there I rode in a jeep driven by Dan Shaver, director of the Nature Conservancy's Brown County Hills Project. Stepping out of the jeep, we stood in the soft winds at the ridge top.
The forest below and all around us is the most successful songbird habitat in Indiana, where populations of the little Cerulean warbler (nearly an endangered species) remain stable, and may even be growing. The Nature Conservancy calls it "The Big Woods".
The Big Woods has many owners. Much of it is already protected as nature preserves, state parks, and national forest. Some areas, though, are privately owned. We were visiting the Bear Wallow Natural Area, where private land mingles with three forest preserves, separating two of them.
The Nature Conservancy is working with private owners, encouraging them to keep their land wildlife-friendly. That way, the private land can continue to serve as a passageway for wild animals to travel safely between government-protected lands.
Such "wildlife corridors" are critical links. They are natural "hallways" between large "rooms" of protected natural spaces. The corridors can be miles wide or as narrow as a road culvert.
About 20 years ago, in response to the rapid disappearance of wild areas, biologists began designing and researching wildlife corridors on different scales for lots of different animals. Today, corridors have been established and more are being proposed.
Wildlife corridors add to the space available to animals and help keep the spaces from being broken up by roads, housing, unsustainable logging, or farming. The corridors help wildlife evade predators and adjust to climate changes. They help animals find food, water, and mates.
They increase the range and "living room" for wildlife. This increases the health and genetic diversity of animal populations and reduces the risk of the animals becoming extinct.
If, on the other hand, habitat continues to be broken up, wild areas become smaller. This is called "fragmentation". If the areas get too small, they may no longer support enough animals to maintain a healthy population. Animals in a habitat that's too small may die out.
In the case of tigers, researchers estimate that at least 50 breeding females are needed to sustain the population. Tiger habitat in Asia is now so broken up that many patches contain 30 or fewer tigers.
Biologists often refer to fragmented habitats as "islands". But, unlike true islands, habitat islands on land can be linked by natural bridges. These bridges provide more overall wild space, so that larger populations of animals can live together and mix. They also may provide escape routes from such catastrophes as drought, flood, disease, or fire.
A farm hedgerow also offers a simple kind of bridge between habitats. On our farm, small animals like chipmunks, squirrels, and deer mice scurry along brushy fence lines between woodlots The brush hides them from hawks and other predators.
Streambanks offer similar cover for the rodents. But even songbirds - although they can fly - are reluctant to cross cleared land.
Some ambitious proposed wildlife corridors would connect national parks to other big habitats for animals that migrate between summer and winter ranges. Other animals require hundreds of acres in which to roam.
In North America, such animals include bears, wolves, lynx, elk, cougars, and panthers. In Asia, tigers and elephants need lots of space. Corridors would let them roam from one place to another safely.
A few years ago, the state of Florida purchased swampland from a lumber company to maintain a green link between the Osceola National Forest and the Okeefenokee National Wildlife Refuge in Georgia.
This wetland corridor contains critical habitat for black bears, sand hill cranes, bobcats, and woodpeckers. The corridor greatly expanded the range for these species.
"El Paseo Pantera" (The Panther's Path) is the name of another proposed corridor in Central America. The idea is to weave a series of protected reserves into a green chain from Guatemala to Panama - one that a panther would feel at home walking along.
But many critical wildlife corridors are much smaller than these. Just five square miles of wild habitat connects a wildlife sanctuary in India to a reserve in Nepal. It lets tigers, elephants, and rhinos move between the two countries.
While habitat corridors are designed to keep animals away from human disturbances, humans often seek contact with wild creatures. This kind of contact can benefit both human and animal. For example, anyone with a backyard bird feeder can help migrating birds.
Birds fly over many barriers that other wildlife cannot cross, but they still need places to rest along the way. Biologists have found that migrating birds use more energy seeking food and shelter along their routes than they do in flight.
Homeowners who live along bird-migration 'corridors' can help by offering seeds as well as a yard with fall-blooming and springtime flowers. Birds also appreciate patches of brush and undergrowth in which to rest.
Backyards with unmown areas along the edges and native plantings of differing heights can also provide 'steppingstones' for wildlife moving along the ground from place to place.
copy; The Christian Science Monitor
