Imported plants and animals that have proliferated in China cost the country nearly 120 billion yuan (US$14.5 billion) every year.

Called alien invasive species, they are brought in from abroad only to end up harming local ecosystems, threaten native species and lead to the loss of local biodiversity.

The problem has caught the eye of the State Environmental Protection Administration and the Ministry of Science and Technology. Together, they are drafting a law on biological security to address the problem.

One example is the water hyacinth, introduced from South America in the 1950s as pig feed, said Xu Haigen, director of the Division of Nature Conservation and Biodiversity of the Nanjing Institute of Environmental Sciences.

Later, as people started using other feed they stopped feeding pigs with water hyacinth.

However, the species reproduced rapidly and spread in provinces such as South China's Guangdong and East China's Jiangsu and Fujian.

The plant covers the water surface, it fights off other water plants and organisms and damages local ecosystems.

Local governments have invested large sums of money to get rid of water hyacinth but all their efforts have failed, according to Xu.

A national survey conducted in 2001 and last year found 283 alien invasive species in the country, ranging from terricolous plants to reptiles and microorganisms.

Nearly 40 per cent of them were considered useful and deliberately introduced, only to prove disastrous for local ecosystems and species.

About 49 per cent entered the country accidentally, traveling on products traded internationally. They then developed wildly.

According to the survey, headed by Xu and experts from ministries such as the State Environmental Protection Administration, the Ministry of Agriculture and the State Forestry Administration, alien invasive species cause direct economic losses of nearly 20 billion yuan (US$2.4 billion) every year.

Direct economic losses are losses in sectors such as agriculture, forestry and fishery. Indirect losses, including damage to ecosystems and species resources in the country, total 100 billion (US$12 billion) yuan every year, he said.

"Many people in the country lack sufficient knowledge about the impact of alien species on ecosystems and the environment and therefore pay no attention to the problem," said Xu, who on Friday in Beijing attended an experts' forum on biodiversity.

Xu proposed a number of steps, including a law on biological safety, strengthening risk assessment capacity, more research on the control of alien invasive species, and raising public awareness.

(China Daily May 22, 2004)