Copyright 2001, Environmental News Network
October 19, 2001
By David Suzuki

Creating "wildlife corridors" to allow animals to migrate between otherwise isolated patches of protected areas has been a popular, although somewhat controversial, idea ever since the eminent Harvard biologist E. O. Wilson first proposed it in the 1960s. Now new studies are showing that such corridors may indeed help improve some species' chances of survival.

Red squirrels are a good example of how corridors can work. These animals used to inhabit much of the United Kingdom, but widespread deforestation in the 19th century pushed them into small patches of forest, mostly in Scotland. There the red squirrels faced pressures from their larger cousins, introduced American grey squirrels, and their numbers dwindled.

For more than a century, red squirrels remained isolated, breeding largely within their own immediate groups and creating genetically distinct populations. Then toward the middle of the 20th century, some of the land separating the squirrel groups was replanted with trees. By the 1980s, the trees had grown to a squirrel-friendly size, creating a corridor — albeit fragmented — of habitat.

But it was enough for the squirrels. During the next 20 years, they used the new patches of forest cover as stepping stones to spread from one patch to the next. Now, according to a recent study published in the journal Science, comparisons of DNA samples taken from red squirrels preserved in the 1920s with modern red squirrels show that populations have bridged the gap and are once again genetically mixed.

Other studies also corroborate the beneficial effects of wildlife corridors. A 1998 review in the journal Conservation Biology, for example, analyzed 32 studies and found that all sorts of animals make use of corridors. Recent studies have also revealed that wildlife corridors can be beneficial for birds and butterflies.

Corridors could prove vital in future conservation efforts. Worldwide, the rate of extinction for plant and animal species is escalating. In the past half-century, for example, tropical forests have shrunk by half. Protected areas exist, but many are too small to support enough genetic diversity for some species to survive. Genetic diversity within species is crucial to help them adapt to changing environmental conditions like the introduction of a new predator or disease, an extreme weather event, or global warming. Isolated populations are also at risk from inbreeding.

Wildlife corridors do have their drawbacks, however. If populations and genes can mix, so can diseases. Corridors are also relatively expensive and difficult to create, involving many levels of government as well as farmers, industry, and property owners. But in spite of the problems, many ecologists feel that creating such corridors is essential to help slow the worldwide loss of biodiversity.

At present, a series of wildlife corridors is being designed for Central America in what is one of the largest conservation projects ever attempted. The project spans eight countries, from Mexico to Panama, and seeks to blend existing parks with buffer zones and protected corridors, creating a web of biological passages that will allow species to migrate from one area to another. Many conservationists feel that the project is an important test case because it's taking place in poor tropical countries, where the greatest diversity of life exists but where biodiversity is also under the greatest threat. If successful, such projects could expand to South America, Asia, and Africa.

Creating wildlife corridors is not the ultimate solution to slowing the worldwide loss of biodiversity, but it is an important step in the right direction. Protected areas alone will offer scant real protection if they are too small to provide enough habitat or genetic diversity for species to successfully adapt to a constantly changing world. Error: Unable to read footer file.