The call came after the State Environmental Protection Administration listed the first batch of 16 alien species earlier this year.

Of the 16 alien species, water hyacinth, mile-a-minute weed, American bullfrog, alligator weed, amazonian snail and bitter bush have rooted in Guangzhou and caused serious ecological problems.

Other than the alien species named in the list, a total of some 40 animals and 11 fungi, insects and animal diseases have damaged the province's farming and forestry industries.

"It is important that the government establish a complete mechanism to evaluate possible damage before introducing foreign species, to monitor alien species' activities and to carry out timely and proper measures to prevent any possible ecological disaster caused by alien species," said Yun Yongli, an official at the provincial pollution control department.

Yun said China was still in the first stages of tackling the problem of invasive alien species and the government is drafting laws and regulations to ensure a safe and healthy ecosystem.

Currently, environmental protection authorities have joined forces with other governmental departments such as customs, forestry and agriculture in a bid to prevent the spread of alien species.

There should also be greater public awareness of invasive species as exchanges with foreign countries increase.

Given their ability to reproduce, adapt quickly to their new environment and establish a sustainable population, alien species are able to dominate the ecosystem, said Xing Fuwu, a professor at the South China Institute of Botany.

Curbing the spread of invasive species is a major task. China spends around 600 million yuan (US$72 million) annually to tackle the spread of alligator weed.

In order to curb the growth of water hyacinth, the province's Zhuhai spends 100 million yuan (US$12 million) annually on destroying the plant.

Xing warned that, so far, there is no effective and efficient method to eliminate invasive species.

Spraying weed-killer is an option. However, using chemicals becomes far less effective when the invasive plants have grown into a large population.

According to Xing, some scientists are working on introducing insects that can eat certain alien plants. Some scientists are also researching to bringing in dodder, a kind of parasitic climbing vine, into the place where mile-a-minute weed grows out of control.

However, from Xing's observations in the wild, dodder cannot completely stop growth of mile-a-minute weed on its own. Using dodder could also have other ecological consequences.

But Xing says there is no need to panic about alien species.

"Not all foreign origin species are invasive. More than 1,000 species now existing in China are of foreign origin. Only several dozen has caused damage to the ecosystem," Xing added.

(China Daily April 11, 2003)