The nets yield almost no fish today, the same as yesterday and the day before that. For generations, Bun Neang's family has depended on the bounty of Cambodia's Tonle Sap, a vast lake fed by one of the world's greatest rivers, the Mekong. Two decades ago, his father could rely on a daily catch totaling about 65 lbs. (30 kg). When the water gods were feeling particularly charitable, he would land a Mekong catfish, a massive bottom-feeder that can weigh as much as a tiger. But today, when Bun Neang dips his net into the caramel-hued waters near Chong Koh village, all the 30-year-old can hope for is a few kilos of sardine-sized fish. Overfishing is partly to blame. But Bun Neang knows of another reason Tonle Sap's big game have all but disappeared. "China," he says of the country that is now tiny Cambodia's biggest foreign investor and economic patron. "Instead of sharing the Mekong, they dam the river and keep it for themselves."
For millenniums, China hardly touched the mighty Mekong, content to let its raging headwaters flow unimpeded from the Tibetan plateau down through Laos, Burma, Thailand, Cambodia and Vietnam. But over the past few years, the emergent superpower has begun turning the world's 12th-longest river into a highway for regional commerce and a source of hydroelectric power. For many Indochinese entrepreneurs, increased China trade and investment has allowed a backward region to participate in their upstream neighbor's remarkable economic expansion. Southeast Asian governments hope China will share the electricity it will harness after a series of massive dams on the upper Mekong are completed in the nation's western Yunnan province. Two have already been built. At least six more are planned.
But for tens of millions of residents downstream, China's efforts to manage the Mekong also threaten their way of life. An astounding 17% of all fish caught in inland waters worldwide come from this generous river, while 90% of the basin's residents are subsistence farmers who largely depend on the Mekong's nutrient-rich waters to feed their fields. Yet Chinese dams, along with engineering projects to make the river navigable by larger vessels, have begun to ravage the river's ecology by blocking sediment and producing unnatural water flows that dissuade fish migration and spawning. The nonprofit Southeast Asian Rivers Network estimates that fish stocks on the Thai-Laos border have already declined by half because of Chinese activity. Farmers, too, complain that the once-predictable floods needed to nourish their paddies have been disrupted by the two existing Chinese dams and the cavalcade of future hydropower projects will only make things worse. "You can't talk about the Mekong today without talking about China," says Carl Middleton, a Bangkok-based consultant for environmental watchdog International Rivers Network. "So much that's happening on the river, whether it's economic, social or environmental, can be linked to China's rise."
Snaking its way from the icy reaches of Tibet to tropical rice paddies near the South China Sea, the Mekong serves as the lifeblood for 70 million people in six different countries. The river's wetlands alone cover an area the size of Ireland, while its fish diversity is rivaled only by the Amazon. But even as many of the world's other majestic rivers the Nile, the Yangtze, the Mississippi were efficiently exploited for trade or hydropower, the 3,000-mile (4,800-km) Mekong has until recently largely escaped the imprint of the modern world. During the colonial era, treacherous rapids stymied expeditions hoping to uncover its upstream secrets, leaving the waterway for local fishermen and farmers. By the mid-1900s, when the West was forced to withdraw from Indochina, the Mekong had become a byword for the failure of modern military might against dogged resistance forces nourished by the river's gifts.
The Mekong is not so unyielding these days. In 2001, Chinese crews, brought in by Southeast Asian governments eager to increase traffic and trade, began blasting and dredging a stretch of the river running from Burma and Laos to Thailand, clearing away islands, reefs and rapids that once blocked the passage of ships. Since then, sleepy Southeast Asian river ports have morphed into boomtowns, with boats from China disgorging cheap electronics, fruits, vegetables and every kind of plastic gadget imaginable. River traffic runs both ways: in December 2006, the first shipment of refined oil chugged up the Mekong bound for energy-hungry China, opening up a potential alternative shipping route to avoid the pirate-infested Straits of Malacca through which roughly half of its imported oil now passes. And with China needing somewhere to park its ballooning foreign-exchange reserves, the riverfront capitals of Phnom Penh and Vientiane now gleam with Chinese-built roads, buildings and other infrastructure. The torrent of investment will likely grow even greater next year when Chinese construction workers finish building a 1,100-mile (1,800-km) Yunnan-Bangkok highway that parallels a section of the Mekong. "Chinese are natural businessmen," says Liu Jingchun, a Chinese boat captain who transports goods between Yunnan and northern Thailand. "For so many years, we shut ourselves off from doing business. Now that we're allowed to trade again, it's like a giant floodgate has opened."