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We Have Met The Enemy...

© Murdo Morrison

"We have met the enemy and he is us." Pogo (Walt Kelly)

We should never forget that the need to make backyard habitats more wildlife friendly arises from human expansion into habitat. Recently I have been increasingly conscious of the fact that, while promoting earth-friendly gardening is clearly important, especially on the local scale, it treats the symptoms while not curing the disease. Local action cannot properly address large scale, potentially global destruction of habitat that is occurring. We need to be concerned and take action at both levels. Some recent studies appear to reinforce this concern.

An article in the February 24 issue of Nature reports that "humanity's destruction of tropical habitat for agriculture, logging and other development has inflated Earth's normal background extinction rate by as much as 1,000 times." This is according to Stuart Pimm, a senior research scientist at the Center for Environmental Research and Conservation who co-authored the article with Peter Raven of the Missouri Botanical Garden. A summary of their findings can be found at UniSci.com.

According to the authors, of an estimated 7 million plant and animal species on Earth, about 85% live on land with approximately two-thirds of them in the tropics, mostly in the rainforests. Pimm and Raven estimate the current loss of forest at about 1 million square kilometers every 5 to 10 years, with several times that area being damaged by fires and selective logging.

A significant percentage (30 to 50% according to the authors) of all plant, amphibian, reptile, bird and mammal species are found in 25 biodiversity "hotspots" that make up less than 2% of the non-ice surface of the planet. Of the 25 locations, 17 are forest areas where over 80% of the pre-existing habitat has disappeared. According to Pimm's estimates, about 20% of the species in these areas have either disappeared or will soon be extinct. The authors conclude that, as the remaining habitat shrinks, the rate of extinctions will increase rapidly and peak before the last surviving species become extinct.

While human activity often plays a major role in habitat loss and species extinction, some plants and animals are particularly vulnerable. A report in the April 14 issue of Science identifies a number of characteristics that expose some species to a greater threat of extinction. According to one of the study's authors, John L. Gittleman, associate professor of biology at the University of Virginia, these characteristics include low population density, long gestation length and limited geographic range. The important point driven home by Gittleman and his co-authors is that extinction events may result in "a further loss of biodiversity, possibly even the extinction or threatening of thousands of additional species of animals." The article is summarized at UniSci.com.

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