Shanghai's environmental protection workers are fighting to rid local waterways of water hyacinth, an invasive aquatic species that has multiplied in the wake of typhoons Wipha and Krosa.

Rivers and lakes in suburban Shanghai, including the Songjiang, Fengxian and Jinshan districts, have recently been clogged with thousands of tons of the floating plants.

File photo: The Suzhou Creek in Shanghai

Water hyacinth frequently invades Shanghai's major waterways, such as Huangpu River and Suzhou Creek, blocking traffic and preventing swimming and fishing. Water hyacinth infestations also stop sunlight and oxygen from getting into the water, while the decaying plants also reduces the water's oxygen content.

The plant from South America, an invasive species endangering biodiversity, has been widely recognized as a harmful weed reducing fish stocks and shading submerged plants.

The city's environmental protection workers are currently engaged in a race against time, fishing out 2,000 tons of the rapidly growing plant from the city's waterways every day.

Outbreaks of water hyacinth do not normally occur in Shanghai until the end of October, but, this year, it started to appear at the end of July.

Since Shanghai has enjoyed an exceptionally long summer this year, the warm climate undoubtedly provides this South American plant with an ideal environment to grow in.

In addition, the two recent super typhoons Krosa and Wipha are another factors behind its boom. "When the typhoons arrived, water hyacinths scattered in the branches of Huangpu River were collected by the strong wind, and covered the river from shore to shore," said Teng Yinbao, vice-director of Shanghai Water Environment Development Company.

"If you leave them in rivers over a while, they make a absolute mess. We must get them out as soon as possible, or traffic on several rivers will be halted," he added.

(China Daily October 14, 2007)