Keeping foreign critters at bay
Hugh MacIsaac tells a hobo story worthy of a Gordon Lightfoot ballad, if the outcome weren't so potentially damaging to North American forests.
An unknown number of diminutive travelers recently jumped ship in Montreal and rode the rails to British Columbia, sharing boxcars with a shipment of stone slabs from Norway. As the wood-crated slabs were transferred from the ship to rail cars, someone noticed a few stowaways but said nothing.
By the time the shipment arrived in British Columbia, however, researchers at a Canadian federal lab there heard about the vagabonds, and put a sample of the packing wood in a sterilized room.
"They found adults of more than 40 different species of bugs, including three species of boring beetles of a type that could wreak havoc with hardwood and softwood forests," says Dr. MacIsaac, a biology professor at the University of Windsor in Ontario.
No one knows whether any of these insects escaped to establish colonies in the New World. "They took a 3,500-kilometer journey, and boxcars are not exactly airtight," he wryly notes.
Variations on MacIsaac's tale are being repeated worldwide as countries struggle to fend off invasive species from invisible organisms to creatures such as the northern snakehead. This voracious freshwater fish native to China has riveted the attention this month of officials from the state of Maryland and the US government.
On one level, bringing "exotic" species into a country can be beneficial if they can be kept local, researchers say. They note that many of the biggest cash crops in the US are imports, for example. But trouble arises when nonnative organisms brought in to control pests, or as food or pets, or inadvertently arriving in ship ballast water, freight packing material, or luggage quickly spread beyond their initial colony.
And while researchers are trying to develop more sophisticated tools to forecast a species' arrival or trace its region of origin, the first line of defense, they say, remains the shippers, fishermen, and tourists who unwittingly serve as transport for these ecological shock troops.
As if to underscore the importance of the issue, this week lawmakers in Washington are circulating a draft revision of the National Invasive Species Act, originally passed in 1990 and reauthorized in 1996. The reauthorization is set to expire this year. The newest proposal would strengthen the federal government's hand in dealing with invasive species, particularly aquatic creatures.
"In the United States and Canada, there's a sense of urgency" about the problem, MacIsaac says.
Indeed, in the US alone, an estimated 50,000 nonnative invasive species cost the country $137 billion a year, according to David Pimentel, an ecologist at Cornell University in Ithaca, NY. He notes that 42 percent of the native species currently listed as threatened or endangered in the US were herded onto those lists by nonnative invasive species.
"Everybody's having this problem," he says, noting similar challenges in Australia, Africa, and Europe, where shipments of US corn to the Balkans in the aftermath of the Bosnian crisis apparently carried insect pests that have gained a foothold in some eastern European countries, threatening their corn crops.
"We're playing ecological roulette," warns James Carlton, a marine scientist at Williams College in Williamstown, Mass., and editor in chief of the journal Invasion Biology.
While the northern snakehead has become the latest poster child for invasive species in the US, other invasive species have been making headlines this summer, including:
the emerald ash borer, a beetle native to Russia that is destroying ash trees in Michigan, Indiana, and may be working its way into Ohio. The borer is thought to have arrived in packing material protecting a shipment of bulk steel from Russia.
three species of Asian carp, which are heading up the Chicago Ship and Sanitary Canal toward the Great Lakes. The carp were originally imported to control algae and shellfish on fish farms in the South. These fish could seriously damage, or even destroy the Great Lakes ecosystem, researchers say, because each female carries as many as 1 million eggs, and adults consume up to 40 pounds of plants, plankton, or shellfish daily.
Japanese shore crabs, which this summer have been spotted near Maine's Penobscot Bay, the northernmost sighting along the East Coast. These tiny crabs are partial to clams, mussels, and lobster the heart of Maine's shellfish industry.
giant hogweed, a member of the carrot family that grows up to 20 feet tall. Native to the Caucasus Mountains and southwestern Asia, the plant was imported as an ornamental, but quickly spread. The plant, newly spotted in western Massachusetts, is considered a potential public-health hazard because its sap sensitizes skin to ultraviolet radiation, according to state environmental officials.
Indeed, biologists who focus on invasive species can tick off a long list of other species that need to be controlled.
"One of the great lessons of invasion ecology that surprises us again and again is what species will do in an environment where they did not evolve," says Dr. Carlton.
Australia and New Zealand have become what MacIsaac calls the "world leaders" in identifying potential invasive species before they arrive. Using statistical techniques and computers to make the comparisons, Australia has developed a database of 300 species and their characteristics to determine which will be let into the country.
So far, MacIsaac says, the invasion model is showing an 88 percent accuracy rate.
"It's so difficult to deal with species after they get in that you have to go to prevention, prevention, prevention," Carlton says.
"Still," he adds, "I am optimistic." He cites a range of examples where agencies, both local and international, are becoming more proactive in confronting invasive species.
Adds MacIsaac, "We've got to be vigilant."
