POYANG, China: Spooked by a historic drought, local authorities in China have renewed controversial plans to dam the country's biggest freshwater lake.

But environmentalists warn damming Poyang Lake, a winter stopover for over half a million birds, would threaten the fragile ecosystem and the endangered birds and other wildlife it supports.

China is currently chairing UN biodiversity talks in Montreal, billed as the 'last best chance' to save the planet's species and their habitats from irreversible human destruction.

The Poyang dam, which is slowly recovering after shrinking to less than a third of its usual size, shows how fraught such efforts are in China.

Conservationist Zhang Daqian said that if realized, the 3,000-meter-long sluice gate across one of the lake's channels would cut it off from the river Yangtze, 'leaving Poyang a dead lake.'

China has built more than 50,000 dams in the Yangtze basin in the past 70 years — including the Three Gorges, which came in the face of widespread opposition from environmentalists.

Over the same period at least 70 percent of the river's wetlands have vanished, according to data from the environment ministry.

When the project was initially proposed, complaints from ecologists succeeded in shelving it.

But the looming specter of droughts — which are becoming ever more frequent and severe in the area thanks to climate change — has altered the calculus.

Poyang supplies water to Jiangxi province's 4.8 million residents, and the local government says damming it will conserve water, irrigate more farmland and improve navigation.

An environmental impact assessment (EIA) published in May gave experts just two weeks to review 1,200 pages of documents and lodge complaints.

Winter visitors