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| Cornell ecologist David Pimentel and his latest book, Biological Invasions: Economic and Environmental Costs of Alien Plant, Animal, and Microbe Species |
But readers of Biological Invasions: Economic and Environmental Costs of Alien Plant, Animal, and Microbe Species (CRC Press, 2002) won't want to tarry too long. An estimated 50,000 "exotics" are causing tens of billions of dollars in harm each year in the United States, according to the new book, and more are on the way. And they're not arriving via spaceships, but in the thousands of aircraft and sea-going ships in everyday commerce, the authors observe.
The book covers many of the more than 120,000 non-indigenous species that have invaded six countries (the United States, United Kingdom, Australia, India, South Africa and Brazil) and gives special emphasis to globe-traveling exotic diseases before making recommendations to help nations slow the influx.
"The impact of invasive species is second only to that of human population growth and associated activities as a cost of loss of biodiversity throughout the world," says Pimentel, a professor emeritus in Cornell's College of Agriculture and Life Sciences. "In the United States, invasions of non-native plants, animals and microbes are thought to be responsible for 42 percent of the decline of native species now listed as endangered or threatened." The names of some invading species are threatening enough. For instance, giant hogweed, a perennial herb in Britain, is blamed for serious dermatitis when it contacts skin. Root-rot fungus is a plant disease spread through Australia by feral pigs, which themselves are non-native down under. Paterson's curse, a weed that invaded Australian pastures, sickens sheep by damaging their livers with plant toxins. Yet the screw-worm fly is a curse to cattle in tropical regions everywhere in the world -- except Australia.
Other invaders sound like they stowed away in shipments of Harry Potter books: Oxford ragwort was deliberately imported from Sicily 's Mount Etna for cultivation in the Oxford Botanic Gardens in the 1700s and now is spreading though Ireland and Scotland; ivy-leafed toadflax was introduced a century before ragwort and now is a common English herb; and paddy brown spot has nothing to do with Paddington Bear but is a serious plant disease that arrived in India on imported seeds and caused the Bengal famine of 1943 in which 2 million perished.
Certain microbes need no introduction, and they didn't need a visa to traverse the continents and cause contagion. Tuberculosis, AIDS, hepatitis, influenza, cholera, bubonic plague are among diseases that the book blames on introduced pathogenic microbes. In the United States alone, health-care costs for AIDS average $6 billion a year, while a single outbreak of influenza can incur $300 million in hospitalization costs and take hundreds of lives, says Pimentel. "An increasing threat of exotic diseases exists because of rapid transportation, encroachment of civilization into new ecosystems and increasing environmental degradation," he writes.
The editor-author and his 44 contributing scientist-writers are careful to note that not all introduced species have entirely deleterious effects in their new homes, and many are depended on for human sustenance. Some 98 percent of the U.S. food supply comes from introduced species, such as corn, wheat, rice and other crops, as well as cattle, poultry and other livestock.
Or take the example of Paterson's curse (Echium plantagineum) on Australia. When the weed's toxic alkaloids aren't ruining animals' livers, its flowers produce nectar used by bees for a pale honey that fetches a premium price in the Japanese market. And in the semi-arid rangelands of northern South Australia, the damaging pasture weed is considered such a useful fodder, when handled properly, that cattlemen call it "salvation Jane." However, economic analysts cited in Biological Invasions call Paterson's curse a mixed blessing to the Outback, with an estimated $30 million in annual costs and only $2 million in benefits.
In fact, only 20 to 30 percent of the 120,000 non-indigenous species become pests and cause major environmental damage, the authors acknowledge. That proportion, however, is more than enough to merit control efforts and attempts to prevent future invasions.
"All introductions of non-native plants, animals and microbes, for whatever purposes -- including agriculture, hunting, tourism, pets, recreation and research -- should be strictly regulated," Pimentel and his co-authors conclude. "In addition, the government should make every effort to inform the public concerning the serious environmental and economic threats that are associated with alien species introductions."
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- Publisher: http://www.crcpress.com/
- Department of Ecology and Evolutionary Biology: http://www.eeb.cornell.edu/