China's Toxic Algae Problem

Zhang Zhengxiang jabs his finger angrily over the water, which shimmers a bright, fluorescent green. That's the color of the toxic algae that now clogs large swaths of the high-altitude, freshwater Lake Dianchi for most of the year. The water may be pretty from a distance, but it's a sign that the lake is profoundly sick. Before the early 1980s, says Zhang, this was a swimming area, and shrimp from the lake were a prized delicacy at high-end restaurants in Shanghai, Beijing and elsewhere. Now the lake's shrimp are inedible, and the toxins in the algae make swimming a decidedly unpleasant experience. Zhang yanks up his trouser leg to show the rash left on his ankles from a recent wade into the once pristine waters. "If you go in, your skin will turn red immediately," says a disgusted Zhang.

China's breakneck economic development has resulted in the world's fastest-growing toxic-algae problem. On the coasts, monster blooms of algae—the "red tides"—have already made many areas a misery of muck, devastating fisheries and tourism. However, toxic blooms on China's freshwater lakes and reservoirs are even more worrisome, since they can have an impact on critical tap-water supplies. This summer the worst-ever such blooms were a media focus in China, as one lake and reservoir after another fell victim to poisonous goop. In May a blue-green algae bloom on Lake Tai caused mass panic when it contaminated the water supply of 2 million residents of the city of Wuxi, in Jiangsu province. Huge blooms were also reported on Lake Chao, further inland. And in late July, 100,000 residents in the northeast city of Changchun went waterless when a toxic bloom appeared on a key reservoir.

Rogue algae are just one symptom of the environmental price China is paying for its roaring economy. Rapid growth has meant a surge in nitrogen and phosphorus pumped into the nation's waterways, which has fed both ocean and freshwater blooms. China and other developing countries are increasingly dependent on freshwater lakes and reservoirs to supply drinking water to swelling populations. Toxic algae can render water undrinkable, cause lung and liver problems and turn shellfish into a deadly dish for humans.

Of course, most algae are harmless. In fact, they produce much of the oxygen necessary for animal life on earth, absorb carbon dioxide, decompose into critical fossil fuels and are the base of marine food chains. Some algae are naturally toxic to humans and other animals, possibly to ward off predators, scientists speculate. Pollution has fattened the algal blooms to unprecedented proportions. Whereas red algae of the ocean feast on nitrogen, the blue-green algae that inhabit fresh water munch on phosphorus—plentiful in fertilizer runoff from farms, factory waste and untreated sewage. Both types of algae can also feed on nutrients from the atmosphere—in acid rain, for example. The link between pollution and algae was speculative until the early 1990s, when the former Soviet Union halted farming subsidies to the Black Sea area. Algae blooms declined dramatically.

The ground zero of China's toxic-algae problem is Lake Dianchi, in the southwestern Yunnan province. The situation is so bad that the nearby city of Kunming is now forced to gets its drinking water from upstream reservoirs instead of the lake. For at least five years running, Dianchi's water has rated 5 or more on a key water-quality index, meaning it's completely useless. One reason: officials can't divert river water into Lake Dianchi to help flush out toxic algae blooms, as they can with lakes further downstream in the Yangtze River system. That's because it's too high—nearly two kilometers above sea level—and fed by small mountain springs, or rivers that are themselves polluted. Nitrogen and phosphorus pour in from all sides and accumulate, turning the lake into the equivalent of a 200-square-kilometer clogged toilet bowl.

Such pollution isn't the only cause of monster blooms. In the Baltic Sea, the overfishing of cod has thrown the food chain out of whack in a way that leaves algae—including the toxic kind—the big winner. Fewer cod has meant more herring and fewer tiny critters called copepods, which are algae's natural predator. Add plentiful nutrients from decades of fertilizer use and untreated runoff from countries surrounding the sea, and the result is goop gone wild: the largest-ever algae blooms were recorded in July 2005 and July 2006, covering almost 150,000 square kilometers. (This year wasn't as bad due to heavy rains.)

The only real solution to China's freshwater algae problem is to curb the amount of phosphorus-rich pollutants that enter the water. That won't be easy. At Lake Dianchi, $660 million has been spent on reducing industrial pollutants, building sewage-treatment plants, intercepting polluted water and banning detergents containing phosphorus. But the situation remains dire. One reason, say environmentalists, is that the government hasn't been willing to crack down on fertilizer use. By one estimate, 40 percent of pollutants that pour into the lake come from agricultural runoff that continues unabated. The farms on the lake's eastern shore produce massive crops of roses and other popular flowers for markets in Asia and beyond. Farmers douse fields with fertilizer to increase yield. One elderly couple wrapping bundles of flowers at a lakeside farm told NEWSWEEK THAT lake water was pumped up the banks to irrigate the flower fields, and then drained—untreated—back into the lake. Bright green algae floated in the drainage ditches dug between fields lined with plastic hutches. Such farms provide livelihoods and critical growth for the local economy—even as they dump noxious chemicals into the nearby lake. "We've been using too much fertilizer in agriculture," says Liu Hongliang, a retired environmental-engineering expert. "[Lake algae] will become more and more serious in the coming years."

Stopping the flow of new pollutants into waterways doesn't clean up the accumulated gunk of decades that's already fouled many lakes and coastal areas. Experts say removing such existing nutrients from lakes is possible but exorbitant—and removing them from coastal waters may be impossible. "How do you empty huge ecosystems of nutrients? There's no easy answer to what can be done," says Henrik Enevoldsen, coordinator at the IOC Science and Communication Center on Harmful Algae in Copenhagen. Humans are turning critical waters to goop through unchecked economic activity. Unless that's curbed, more and more will suffer the toxic fate of China's Lake Dianchi.