To determine the true toll, the Three Gorges Dam is taking on animal and plant species, Liu says, long-term data is needed, so that decreases in population totals can be compared with natural species fluctuation. But he cautions that many of the dam's effects may not be immediately apparent. The project is altering reproduction patterns, meaning it may already be too late for some plants and animals. "In the short term, you see the species still there, but in the long term you could see [them] disappear," Liu says. It is here that State Council representative Wang's allusion to "hidden dangers" rings especially true.
Disease and Drought
When officials unveiled plans for the dam, they touted its ability to prevent floods downstream. Now, the dam seems to be causing the opposite problem, spurring drought in central and eastern China. In January, the China Daily (the country's largest English-language newspaper) reported that the Yangtze had reached its lowest level in 142 years—stranding dozens of ships along the waterway in Hubei and Jiangxi provinces. An unnamed official with the Yangtze River Water Resources Commission blamed climate change, even as he acknowledged that the dam had reduced the flow volume of the river by 50 percent. To make matters worse, China is now plowing ahead with a controversial $62-billion scheme to transfer water from the Yangtze to northern China, which is even more parched, through a network of tunnels and canals to be completed by 2050.
Meanwhile, at the mouth of the Yangtze residents of Shanghai, China's largest city, are experiencing water shortages. The decreased flow of fresh water also means that saltwater from the East China Sea now creeps farther upstream. This, in turn, seems to be causing a rise in the number of jellyfish, which compete with river fish for food and consume their eggs and larvae, thereby threatening native populations that are already dwindling as a result of overfishing. In 2004, a year after the dam was partially filled, scientists noted a jellyfish species in the Yangtze that had previously only reached the South China Sea.
The effects of the dam's disturbance of whole ecosystems could reverberate for decades. G.W.'s Davis is part of a project researching the disease schistosomiasis (a.k.a. snail fever or swimmer's itch), a blood parasite transmitted to humans by snails; people can get it by swimming or wading in contaminated fresh water when infected snails release larvae that can penetrate the skin. (Symptoms include fever, appetite and weight loss, abdominal pain, bloody urine, muscle and joint pain, along with nausea, a persistent cough and diarrhea.) The snails used to breed on small flood plain islands where annual flooding prevented a population explosion. Now, the decreased flow downstream from the dam is allowing the snails to breed unchecked, which has already led to a spike in schistosomiasis cases in some areas.
According to Davis, such alterations could precipitate a rise in other microbial waterborne diseases as well. "Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region," he says, "you change a lot of environmental variables. Almost all infectious diseases are up for grabs."
The official recognition of the dam's dangers suggests that the project's environmental and public health impacts are starting to sink in. Political analysts speculate that President Hu Jintao and Premier Wen Jiabao are eager to distance themselves from a project they inherited. Although halting plans at this point would be an admission of government error, the openness following the Chongqing meeting raised the hopes of worried scientists that officials would take action to minimize the project's environmental and public health fallout.