Let the invasions begin
by Cherie Winner | © Washington State University
As Beijing prepared to welcome athletes and spectators to the Olympic Games, a quieter and much less welcome influx was already under way.
According to a new study by Washington State University ecologist Richard Mack and four Chinese colleagues, China's explosive economic growth and ambitious public-works projects have allowed non-native species of plants, insects, and other organisms to spread throughout the country and inflict more than $14 billion of damage on the nation's economy—and the Olympic Games could provide an opportunity for even more biological invaders.
Mack and his co-authors combed through trade and economic data to discover that China's economic boom has been accompanied by a boom in biological invasions.
"They're compressing the whole Industrial Revolution into about 40 years—and on a bigger scale," says Mack. In the past 30 years, for instance, the number of international ports of entry in China has doubled and the total length of express highways has expanded by 40-fold. Over the same period, the number of invasive species in the country has more than tripled.
The movement of introduced species across the nation has occurred at breathtaking speed and enormous cost. The American vegetable leaf miner, Lyriomyza sativae, was first detected in Hainan Province in December 1993. By early 1995 it had spread to 20 other provinces. It now occurs throughout the whole country and causes at least $80 million in damages to vegetable crops every year.
China's waterways have also become distribution systems for biological invaders. The Three Gorges Dam and a major canal project diverting water from the damp south to the drought-prone north could provide easy migration routes for aquatic invaders such as water hyacinth and alligator weed. Both plants periodically block waterways in southern China and have the potential to clog power turbines and water-intake pipes.
The Olympics add another challenge to Chinese ecosystems: the entry of untold numbers of non-native seeds, spores, and insect eggs that will hitch a ride with the thousands of visitors and cargo containers converging on Beijing this summer.
Mack says the Chinese government recognizes the potential of the Games to lead to further problems with invasive species and is working on ways to detect and eliminate them before they gain a foothold. However, he and his colleagues also found that between 2002 and 2004, the Chinese government imported more than 31 million woody seedlings and 130,000 pounds of seeds to be planted in and around Beijing to beautify the city in advance of the Games. Some of those plants may themselves become invasive, and even well-behaved imported plants may carry invasive insects or parasites.
According to Mack, the most critical phase of the effort to deter Olympic invaders will come after the human visitors have moved on.
"The most likely way that any of these organisms are going to come in is in a resting stage—eggs, seeds, spores," says Mack. "That means they're not going to be prominent at all when they first come in. So the Chinese will need to be alert with follow-up inspections."
Programs to detect newcomers should continue for more than a year after the Games end, he says—the longer the better, because spores and seeds may not start growing right away. Mack told Chinese scientists about one of the first such inspection efforts, which occurred in Philadelphia following the city's big Centennial Exposition in 1876.
"The city assembled a group of local botanists to walk the
grounds of the exhibition halls for four years after it was over,
looking for new species that would have come in. I consider that
incredibly insightful," he says.
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