UPHILL BATTLE: A backhoe scoops water hyacinth from the Shuikou Hydropower Station reservoir in Fujian Province on April 27 (ZHENG ZUZHI)

The Convention on Biological Diversity, a global agreement addressing all aspects of biological diversity, states that the invasive species problem continues to grow at great socio-economic, health and ecological cost throughout the world. Invasive species exacerbate poverty and threaten development through their impact on agriculture, forestry, fisheries and natural systems. This damage is aggravated by climate change, pollution, habitat loss and human-induced disturbances.

Continuous battles

Beijing launched a campaign in 2007 to thwart assaults by alien insect species on the city's trees to ensure plenty of greenery for the 2008 Olympics.

The American white moth, Hyphantria cunea, a native to North America was one of these insects. It was first detected in Liaoning Province in 1979. It now poses a threat to forests and crops in 116 counties of six provinces and municipalities including Beijing, Tianjin, Hebei and Liaoning, according to the State Forestry Administration (SFA). The species was first spotted in Beijing and surrounding areas, including Tianjin and Hebei, in 2005.

Wei Diansheng, Director of the SFA's Forestation Department, said a brood of American white moth larvae can eat all the leaves off a healthy tree in just a few days and a single female can produce up to 200 million offspring every year.

An investigation by the SFA showed that in 2005, 156,000 hectares of trees were stricken by the moths. They had spread to an additional 67,000 hectares the following year.

At that time, Beijing took many measures. Officials teamed up with their counterparts in Tianjin, Hebei and other surrounding provinces to fight against the moths. They sprayed insecticide, made light traps and cultivated the moth's natural enemies, such as parasitic wasps that feed solely on the moth's eggs, said Wei.

Beijing, Tianjin and three other nearby provinces pooled about 66 million yuan ($9.66 million) to help pay for the effort.

"It is impossible for us to wipe out the moths in one or two actions. A long-term project is necessary," said Wei.

He said the SFA has formed a long-term cooperative effort with the meteorological administration in a bid to predict potential attacks by pests and other harmful species.

Ding Jianqing, a senior researcher at the Wuhan Botanical Garden affiliated with the Chinese Academy of Sciences, said Beijing's move against the moths constitutes just one battle in the national war to control invasive species.

Water hyacinth, another typical invasive alien species in China, is creating a serious problem in rivers, lakes and ponds in south and east China.

Water hyacinth was introduced to China from tropical South America as flowers and pig feed. When not controlled, it dramatically impacts water flow, blocks sunlight from reaching native aquatic plants and starves the water of oxygen, often killing creatures living there. It also creates a prime habitat for mosquitoes. Chemical and mechanical removal is often too expensive and ineffective to deal with the plant.

Yang Hongjun, Director of the Yunnan Ecology Agriculture Institute, said China spends 500 million yuan ($73 million) to 1 billion yuan ($146 million) every year dealing with the pesky plant that it imposes annual direct economic losses totaling around 10 billion yuan ($1.46 billion).

Yang said the battle against water hyacinth will still go on and authorities are trying to find efficient solutions.

Tackling the problem

"The most effective control method remains the prevention of the spread of alien invaders," said Zhang Runzhi, a researcher at the Chinese Academy of Sciences' Institute of Zoology.

He said the introduction of invasive alien species involves intentional and unintentional imports.

Intentional imports usually include bringing species into the country for breeding, planting and flowering, while unintentional imports refer to those brought in through aircraft, land traffic and waterway transportation.

Authorities always found in hard to control intentional imports, which inevitably led to the spread of invasives.

To counter the threat, said Wang, early warning, monitoring and response systems have been set up nationally, with more than 1,800 stations, 30,000 inspectors at nearly 700 ports and 35 quarantine bureaus established in 31 provinces, municipalities and autonomous regions.

"We should also forbid the use of imported alien species in all vegetation restoration schemes, promote the use of local species and research the seedling sources and sustainable use of local species," said Xie.

Development and updating of a list of dangerous invasive species and the establishing of a convention to limit the spread of these species are also priorities, said Xie.

China has seven laws on the books—the Agricultural Law, the Law on the Entry and Exit of Animals and Plants Quarantine, the Grassland Law, the Seed Law, the Fisheries Law, the Forest Law and the Wildlife Protection Law. Several other regulations also apply to the issue. "The role of the existing laws is limited to customs and cannot govern species introduction. We need a more effective law for that urgently," said Zhang.

He said the law should stipulate a unified governing organ and a spending budget to train and equip local workers to identify and help prevent the spread of alien species.

Invasive species are a global issue that requires collaboration among governments, industries and non-governmental and international organizations, Zhang said.

"International cooperation between source and host countries helps researchers on the other side to quickly identify the alien species and understand their habitats," he said. "Meanwhile, outbound customs inspections can provide the first barrier to species flowing into other countries."

It is also important to develop economic tools and incentives to help prevent introductions, and to educate the general public and raise awareness so that informed decisions can be made about how to limit and contain introductions, said Wang.

"Raising people's awareness is important because individuals also have a large part to play. To win this war we need the help of policymakers, consumers, horticulturalists, landowners, educators and the youth," he said.