Gulangyu, a small scenic island off the southeastern coast of China, is under attack from a tiny climbing plant nicknamed Cat's Claw.  

Many old Western-style mansions on the island, built in the early 20th century, have been blanketed by thick Cat's Claw vines and people worry they will slowly destroy the buildings.

"Cat's Claw grows everywhere and it is almost impossible to get rid of it," said Wang Huade, who lives in a mansion that was built in the 1920s.

A 290-year-old Chinese banyan on the island is suffering from Cat's Claw as well. Vigorous Cat's Claw vines will strangle the tree if it covers all of its trunk one day.

Cat's Claw (Macfadyena unguis-cati), originating in South America, was first planted on the island in the 1920s as an ornamental vine but was seldom seen some 10 years ago. But things have changed since then.

"Cat's Claw has harmed the biological diversity on the island. Many trees have died from it," said Professor Lu Changyi from the Environmental Science Institute of Xiamen University.

A similar problem is troubling Southwest China's Sichuan Province. In Liangshan, in the province's west, hillsides are densely covered with Crofton weed, believed to have migrated across the border from Southeast Asian countries, leaving no room for local weeds.

By air, land or sea, biologic invaders are coming into China with growing international trade.

In 1996, every 30,000 tons of grain imported through Shanghai port contained 120 tons of exotic grass seeds. About 10 million tons of food was imported that year.

Besides invaders from foreign countries, those moving between China's regions have also been reeking havoc.

In the southwestern province of Yunnan, two-thirds of local fish species became endangered after new fish were introduced from the middle and lower reaches of the Yangtze River.

The annual output of a unique fish in Yunnan's Fuxian Lake dropped from about 500 tons in the 1960s to 1 ton in 2002.

"Our defense against biologic invaders has severe weaknesses," said Doctor Xie Yan from the Chinese Academy of Sciences, who compiled the first report and a book about exotic biologic invaders in China with her colleagues.

"The problems result from human activities," she said. "New plants and animals are carelessly introduced from other regions and countries to meet the needs of agriculture, gardening or environmental purposes.

"Half of the harmful exotic biologic invaders in China were intentionally introduced."

Green areas in downtown districts are favored and China imported more than 2,000 tons of grass from abroad in 1997. The grass has taken over local species.

"Our laws and regulations are not sound enough to hold up against exotic invaders," said Yang Chaofei, the former director of the Natural Ecology Protection Department at the State Environmental Protection Administration.

Present quarantine laws and regulations are mainly against plant diseases and insect pests.

Too few people devote attention to supervising plant and animal introductions to keep out biologic invaders, Yang said.

Lack of awareness of the danger of biologic invaders is another major reason, Xie said.

On the island of Gulangyu, a plant resource census completed in the early 1990s found that a seaside wood had been overwhelmed by Cat's Claw vines but it roused little attention from the public and the government.

"There is also pressure from the trade in exotic plants and animals for profit," Xie said.

China has several hundred exotic biologic invaders in some 30 provinces, autonomous regions and municipalities, including 1,900 natural reserves.

Environmental experts are calling for stronger links among relevant government departments such as environmental protection, agriculture, forestry, trade and quarantine, to combat the dangers.

Many government departments are only talking at the moment and no effective policies have been put forward, Xie said.

"Items to protect biological diversity should be added into laws, and be followed by supervision and punishment," she said.

Some also suggested that the Law on the Protection of Wildlife should be amended to ban natural reserves from introducing dangerous external species and forbid people from feeding wild animals in natural reserves.

(China Daily July 6, 2004)