It's a Two-Way Street

As China Booms, Invasive Species Flood in
Jessica Marshall, Discovery News

April 3, 2008 -- It's not just China's economy that's booming. Invasive species are thriving there, too.

Non-native organisms are arriving in growing numbers thanks to increased trade. And they are penetrating once-isolated areas now accessible via new transportation routes.

"The furthest reaches of the country are now being reached," said ecologist Richard Mack of Washington State University in Pullman, Wash., who reported the findings with Chinese colleagues in the April issue of BioScience.

By any measure, China's trade and transportation infrastructure are growing like weeds.

Mack and colleagues reported that since China opened its doors to global trade in 1978, the value of its imports and exports has exploded from $20.6 billion to $1.4 trillion in 2005. The number of international ports of entry has doubled since 1987. By 2005, more than 25,000 miles of express highway threaded through China compared with 620 miles in 1988.

This growth has brought with it exotic species -- some imported deliberately as garden plants or pets, and others introduced accidentally, hitchhiking in products or packaging materials.

The group found that the number of documented invasive plant species in China more than tripled between 1995 and 2003, while animal invaders increased 30 percent from 1990 to 2003. Its roster of 400 invasive species costs China a minimum of $14.5 billion a year, according to an estimate cited by the researchers.

"This is just what happens with international trade," Mack said.

For decades the United States has battled its own invaders, including increasing numbers of Chinese species like the Asian longhorned beetle, which arrived in 1996. Now North American species are causing damage in China. The fall webworm, for instance, has attacked more than 200 plant species in Beijing and elsewhere, chewing leaves down to nothing.

As Mack pointed out, "It's a two-way street."

Aquatic plants may cause some of the worst damage, said James Quinn, ecologist at the University of California, Davis, who was not involved in the study. "Water hyacinth and others can completely destroy a waterway," he said. Such plants already block passage through canals during flood season in the south of the country. They may find their way north more quickly once the massive South-to-North Water Diversion Project is complete. The project will carry water to the north of the country through a system of three canals.

"It's a direct conduit along which these aquatic species can move across the country," Mack said.

China's attempts to beautify Beijing in advance of the 2008 Olympic Games may further exacerbate the invasive species problem. From 2002 to 2004, more than 31 million non-native seedlings and 132,000 pounds of seeds were planted in the city.

"It will definitely be a hidden cost of the Olympics," said William Gregg, former program coordinator for the U.S. Geological Survey Invasive Species Program in Reston, Va.

These plantings may not themselves become invasive, Mack said, but they may bring hitchhikers, and invasions may take time to develop. The good news is that authorities in China are keen to improve quarantine and inspection procedures for the Olympics and beyond, he added.

"Whatever they do, it needs to go well beyond the time that the games are held," he said, pointing to an unusual moment of foresight in U.S. history.

When the city of Philadelphia held a centennial exhibition in 1876, a botanist checked the grounds for four years after the event to look for any new species.

"I think, frankly, we'd have fewer of our own problems with invasive species if that kind of foresight had continued," Mack said.