When species such as the giant African snail (right), zebra mussel or Nile perch relocate, they trash the neighborhood in no time. The move frequently upsets the local ecosystem to such an extent that many native species become extinct. Indeed, alien invasions are second only to habitat loss in causing species extinction worldwide. But an international team of scientists, lawyers and policy makers¿termed the Global Invasive Species Programme (GISP)¿is working to develop a game plan for curbing the damage, which Stanford professor Harold Mooney presented at the annual meeting of the American Association for the Advancement of Science last Friday. "We¿re looking at designing something like the CDC [Centers for Disease Control]," Mooney says. "We need something comparable for invasive species."

The problem cannot be understated. Take, for instance, the example of immigrant brown tree snakes on Guam. The creatures have already driven 10 species of forest birds, six species of lizards and two species of bat into extinction. Putting biodiversity aside, they hurt business on the island by slithering over power lines and causing blackouts and by hunting in family chicken coops. Water hyacinths have similarly crippled Africa¿s Lake Victoria area, and crazy ants have upset Christmas Island. Closer to home, the star thistle is muscling native desert grasses out of California. "The rangelands of the west are being taken over by noxious weeds causing enormous financial loss," Mooney says. A 1999 survey estimated that introduced species of animals, plants and microbes cost the U.S. $123 billion a year.

The GISP group met last September in South Africa to finalize a 10-point global strategy. Part of that plan addresses the need for establishing financial checks and balances. "If you import something, and it gets away, you should have to pay," Mooney says. He has proposed setting up a type of bond or insurance system such that importers contribute to a special fund set aside for coping with emergencies. "If we have a fire, then we send for the fire trucks. People respond right away," he adds. Given a similar "rapid response mechanism" for invasive species, nations should be able to contain the problem, thereby saving the additional money and effort it would take to deal with the situation later on.