Think Twice Before Opening the Door to Exotic Plants

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As disposable incomes rise in China, the desire to alter the landscape is intensifying. City authorities, tired of the same old surrounding flora, are eager to revitalize streets and parks with new and exotic greenery. Meanwhile, desertification researchers, faced with worsening sandstorms from China’s barren deserts, are keen to find more permanent methods for holding back the drifting sand. These groups, different as they appear, occasionally arrive at the same solution: introducing exotic plants. With these “dream” plants, however, come potential threats to both local ecosystems and the economy.

Some exotic plants, once settled into their new environments, evolve into fast-spreading invasive species, wiping out native vegetation and causing huge economic losses. Currently, at least 380 of the more than 400 invasive species found in China are plants (the rest are animals and microorganisms). Experts estimate that these invaders have caused annual losses to grain production of 10-15 percent, to cotton of 15-20 percent, and to fruits and vegetables of 20-30 percent. Total direct and indirect economic losses incurred by all invasive species in China amount to 120 billion RMB (approx. US $14.3 billion) annually, roughly 1.4 percent of the gross domestic product, according to China People’s Daily.

A national survey of invasive species in December 2001 found that nearly 40 percent of the 283 invasive species identified at the time were introduced intentionally, nearly the same percentage (44 percent) as were brought in accidentally through trade and transport. (The remaining 16 percent entered the country either through natural pathways, such as being carried by wind and birds, or other means.) According to the Institute of Botany at China’s Academy of Sciences, 58 percent of invasive plant species were introduced for agricultural, forestry, and gardening purposes.

Water hyacinth (Eichhornia crassipes) and Canada goldenrod (Solidago canadensis) are examples of two invasive plants that were introduced in China for ornamental purposes but have since caused serious damage. Water hyacinth, native to South America, was first introduced in gardens in 1901, and then planted widely during the 1950s and 60s for use as a pig feedstock. Alternative feeds have since taken over the market, but the hyacinth has remained, invading waters in 17 provinces and municipalities across China. Its thick leaves form dense sheets on the water surface, clogging rivers, polluting lakes, suffocating fish populations, and destroying local freshwater ecosystems.

Before the 1960s, 1,000-hectare Dian Lake, the largest freshwater lake in Yunnan Province and the sixth largest in China, boasted 16 types of water plant and 68 aquatic species. By the 1980s, however, most of the plants, and more than half of the species, had been choked out, primarily by the water hyacinth. In 2002, experts estimated that the annual economic loss to China from the hyacinth was nearly 10 billion RMB (approx. US $1.2 billion)—a cost that has likely increased as the affected area expands.

Canada goldenrod was first introduced in Shanghai and Nanjing in the 1930s. With its strong reproductive ability, however, it has spread quickly along China’s east coast, destroying native vegetation along the way. Over time, the goldenrod has become one of the most insidious weeds in Shanghai and has wiped out more than 30 local plants. It has also encroached upon farmlands and orchards, degrading arable lands and causing huge losses to fruit, cotton, maize, soybean, and rice production.

So far, China has no sufficient legal or technical shield against invasive plants. A comprehensive law on prevention and treatment of invasive species has been in the pipeline since September 2004, but is still under deliberation. There is no sound mechanism for assessing the risks related to exotic species introduction. Given the current lack of knowledge about these risks, proponents of beautification and other groups should exercise caution in bringing additional exotic plants into the country. A safer alternative would be to utilize native plants in urban gardening, anti-desertification efforts, and other endeavors. As history has shown, the grass is not always greener on the other side of the fence.