Venezuelan alert over lake weed

By James Menendez
BBC News, Caracas

No-one is sure what is causing the rapid growth of the weed

Efforts are under way to try to control an aquatic plant which is threatening to choke one of South America's largest bodies of water.

"Duckweed" or water lentil - a floating green plant - already covers a quarter of western Venezuela's Lake Maracaibo, according to some estimates.

Officials in the area have declared a state of emergency as the lake is turning green at an astonishing rate.

In just two months, vast areas have disappeared under thick vegetation.

Efforts to clear the weed-like plant have so far failed to keep up with the rate at which it is growing.

Local fishermen have been unable to launch their boats.

And scientists are worried that, although it is not toxic, the plant may be starving other species in the lake of nutrients.

Government estimates suggest it currently covers 1,500 square kilometres.

But local scientists believe the affected area is closer to double that size.

Race for solution

No-one is certain what caused the problem.

Experts believe it may be linked to recent heavy rains, which contaminated the water.

Lake Maracaibo is certainly no pristine wilderness.

Instead, it is one of Venezuela's biggest centres for oil production and export.

The state oil firm says shipments have not been affected.

But the authorities are racing to come up a solution which does not involve removing huge quantities of vegetation by hand.

The environment ministry said it was trying to find out whether there was a safe biological or chemical way to stop the plant spreading.