By RHITU CHATTERJEE
In 2003, more than 50 people in the Midwest became ill with the monkey pox virus. The source for the African pathogen – pet prairie dogs that were kept next to infected Gambian pouch rats in a pet store.
In the early 1970s, Arkansas aquaculturists imported the Asian Black carp to control fish parasites in aquaculture ponds. Now these mussel-eating fish are happily lurking deep in the waters of the Mississippi River Basin. Scientists fear that they may be driving precious endangered snails and mussels to extinction.
Meanwhile, released pet Burmese pythons are competing with native alligators in the Florida Everglades for food.
All these cases have one thing in common – the troublesome animals were imported into the United States for commercial purposes.
Few non-native species transported for trade – aquaculture, aquarium, pet, nursery or live bait trade – survive in their new environment, and fewer still become established and cause problems. But the damage done by those few is large enough to cost the United States billions of dollars every year.
Once a non-native organism is established and spreading in its new home, eradication efforts are pointless and often have widespread adverse environmental effects. That is why ecologists and environmentalists are stressing on the need for risk assessment and prevention.
Twenty years ago, this might have been impossible. Now, however the situation is different.
Scientists and environmentalists agree that targeted control of trade in live animals and plants would prevent a significant portion of the problem right at the roots. In 2006, the Ecological Society of America announced that scientists have the tools for doing risk analysis on species being transported. A 2007 study by economist David Finnoff at the University of Wyoming and colleagues has shown that even without accounting for environmental costs, Australia's plant quarantine program – which identifies potentially risky plants and bans their import – saves the country billions of dollars in herbicide, pesticide and labor costs.
Currently, the United States reacts rather than takes a precautionary approach to non-native species. According to an investigative report released by the Defenders of Wildlife in August 2007, by the time federal agencies step in, damage is already done. The Centers for Disease Control and Prevention, the U.S. Department of Agriculture, and the U.S. Fish and Wildlife Service address human health, agriculture, and wildlife implications, respectively.
The U.S. Fish and Wildlife Service is the slowest to respond among the agencies and has the least regulatory authority to prevent potential invasions, followed by the CDC, says Peter Jenkins, main author of the Defenders of Wildlife report. The agriculture department is the "least guilty," he adds.
The first step for risk assessment of alien species is screening of organisms being imported. International databases of species known to be harmful can help government officials in deciding whether or not to let a species in.
The Defenders of Wildlife report found that of the 2,241 identified nonnative animal species imported into the United States between 2000 and 2004, as recorded by the Fish and Wildlife Service, 302 species were easily identifiable as potentially risky from international databases and other historical records. Yet they were allowed to be brought into the country. More than a billion individual animals imported during that time were not even identified.
Even species with no previous history of causing trouble can be evaluated for potential harm. Recently developed tools, called quantitative models, can predict whether a species is likely to cause problems with 80- to 90- percent accuracy – even with relatively little information on the species. These tools are being finetuned for higher accuracy.
Organisms whose risks cannot be easily assessed could be allowed into the country, but monitored closely afterward for a prompt response in case of any problems. Using the case of the invasive rusty crayfish in the Great Lakes region, David Lodge of University of Notre Dame in Indiana and his colleagues have showed that even with species that have just become established in a new environment, simple models with the available, preliminary data can be used to predict its invasiveness. And prevention of further invasion if done in the early stages is possible with simple educational measures that yield big economic benefits.
Australia and New Zealand adopted these measures years ago, opting for environmentally safe animal and plant trades. They are continuing to save billions of dollars that would otherwise have gone into hopeless efforts to manage non-native species when it is already too late.
Rhitu Chatterjee invaded the United States fro India in 2002 and reports for Environmental Science & Technology.