Benefits Of Alien Species
July 28, 2000
Professional ecologists are appalled at the spread of non-native forms of life to new areas. They want international controls to prevent the spread of all "invader species." David Pimentel, an ecologist from Cornell University, estimates that the 50,000 nonnative species in North America cost the economy $137 billion annually.
But other scientists say the obvious benefits of alien species should be weighed against the costs.
- For instance, 99 percent of crop plants in the U.S. are nonnative -- as well as all our livestock, except the turkey.
- On the other hand, 60 percent of insect pests are native species.
- And the introduction of new species into an ecosystem tends to raise the total number of species living there -- increasing biodiversity, rather than decreasing it.
A case in point is the zebra mussel, introduced into the Great Lakes via discharged ballast water from European freighters. The University of Maryland's Mark Sagoff, who has worked with the state's Sea Grant program, points out the benefits from the mussels.
- In the Great Lakes, the zebra mussels were found to strain algae and nutrients -- like fertilizer runoff -- and play a significant role in improving water quality by clearing the lakes of polluting organic matter.
- The U.S. Geological Survey reported that water quality in Lake Erie improved dramatically after the introduction of the zebra mussels, by some measures four to six times what it was before.
- The increased water clarity allows more light to penetrate deeper and support more aquatic plants that provide food and habitat for native fish and ducks.
Source: Ronald Bailey, "Bio-Invaders," Reason, August-September 2000.
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