As the Olympic Games approach, China has come under fire for its environmental track record. Tales of Beijing and other cities' infamous pollution and images of highly polluted lakes and rivers have met with demands for action, both within China and internationally, and have produced some meaningful results. Yet another environmental crisis looms: biological invasions. Indeed, while perhaps not as overt as choking smog or pea-green water, the ecosystems of this vast nation are increasingly threatened by invasive species.
Invasive species are non-native species, introduced by humans into the native environment. Species are introduced for a variety of reasons. For example, exotic plants are often transported across the globe for decorative plantings in gardens. Tropical and other exotic fish are shipped for use in personal fish-tanks and large aquariums. Oftentimes, species' release into the environment is unintentional – for example, non-native mussels or seaweeds unknowingly carried on the undersides of boats.
Many invasive species have specific characteristics that allow them to succeed in their introduced environments. They often grow rapidly, which leaves less time for indigenous species to adjust or adapt to their presence. They also do well in disturbed environments: weeds often thrive on the sides of roadways and aquatic plants flourish in man-made canals. If species are allowed to invade, establish themselves, and grow unchecked, they can often drive native species to extinction, a consequence that has been well documented.
Water hyacinth, an invasive weed introduced from South America in 1901, clogs the riverside in Fubao, China. Weed invaders cause an estimated $7 billion in damages each year. Photo from Changua Coast Conservation Action via Flickr.
Yet the effects of biological invasions are not limited to ecosystems or natural environments. Several studies have detailed the far-reaching negative consequences that invasive species can have on economic growth. This is particularly relevant to China, which in August will host the Olympic Games.
Much of the Chinese economy's unprecedented growth has been driven by increased international trade. As the country's trade infrastructure has expanded, so has its vulnerability to biological invasions. In the last 20 or so years, the number of international ports in China has doubled, and the multi-lane highway network has grown from only 1,000 to more than 40,000 kilometers. And since 1990, the number of invasive species has grown by a factor of ten (see Figure 1).
The problem has been exacerbated by increased canal building and damming, including the Three Gorges Dam (the world's largest). In particular, many canals are being built to transfer water from the wetter south to the semi-arid north, which often suffers extended droughts. These new waterways provide an ideal mode of transport for many kinds of invasive species, especially aquatic weeds, which regularly clog hydroelectric turbines on many of China's rivers.
Figure 1: Exotic pest species intercepted, 1999-2005
As international ports and other transportation infrastructure have expanded, the number of exotic species intercepted by the Chinese border patrol has increased significantly. Source: Ding, et. al., 2008.
Another major area of concern is the newly opened Qingzang railway, which connects inner China with the autonomous region of Tibet. Due to its remoteness and altitude, Tibet has until now been largely unaffected by China’s growing invasion problem, but the new railway will bring increased transport and new goods and people that may carry potential invaders with them. Climate change also presents a challenge to this isolated region. (Ironically, warming temperatures have melted large tracts of permafrost along the elevated train tracks, damaging the parallel trucking road and causing potential structural issues for the rail line.) Warmer temperatures also mean that species once unable to live on the high, cold Tibetan plateau may now be able to move in and establish themselves as invaders. Native Tibetan species, unaccustomed to the entry of foreign species, will probably be unable to cope, as has happened in other isolated ecosystems like Hawaii and Tahiti.
In China alone, potential damage from invasive species is estimated at nearly $15 billion annually. One pest in particular – Liriomyza sativae, the American vegetable leaf miner – has damaged large swaths of crops in more than 20 Chinese provinces, causing an estimated $80 million in damages.As the opening ceremonies of the 2008 Olympic Games approach, invasion experts are worried that the massive influx of athletes, spectators, and plane- and boatloads of cargo that will accompany them will also bring a host of non-native species to China. Foreign species have also been purposefully introduced: in preparation for the games, officials in Beijing imported more than 31 million plants and an estimated 130,000 pounds of seeds as part of a citywide "beautification" project.
Many of these plants are non-native and may become invasive, or may carry non-native insects and pests with them. And since many invasive species take some time to establish themselves and begin their takeover, experts are urging inspection and surveillance after the Games have concluded. As millions of people come from around the world to discover and experience all that the nation has to offer, China will be working to ensure their visitors don't leave behind unwanted guests.
Top photo of a plant damaged by leaf miners from Gavatron via Flickr
RELATED LINKS:
"China's Booming Economy is Sparking and Accelerating Biological Invasions," BioScience (April 2008)
National Invasive Species Information Center
IUCN/SSC Invasive Species Specialist Group (ISSG)
EARTHTRENDS:
Feature: "Alien Flotillas: The Expansion of Invasive Species Through Ship Ballast Water"
Feature: "Bioinvasions: Stemming the Tide of Exotic Species"
Map: Non-Native Plant Species in Grasslands in North America
Searchable Database: Biodiversity and Protected Areas
