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http : //www . enn . com/extras/printer"friendly . asp ?storyid=45299 9 Wildlife corridors give species breathing room By David Suzuki Friday, October 19, 2001 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 . 1 of 2 11 / 1 /2001 11 : 10 AM