China doesn't do anything small. And it's the massive scale of the series of electricity-generating dams it began building on one of the world's great rivers, the Mekong, in 1986 that is worrying observers downriver. A May report by the U.N. Environment Program and the Asian Institute of Technology warned that China's plan for at least eight dams could present a "considerable threat" to the river and by extension to some 60 million people in Vietnam, Cambodia, Thailand and Laos who depend on it for water, food and transportation. A petition presented to the Prime Minister of Thailand in June bore more than 16,000 signatures, including those of subsistence farmers and fishermen fearing for their livelihoods. But critics' objections have been muted, some analysts said, by China's ascendance on the world stage and undermined by plans for Laos, Cambodia and Thailand to build dams of their own.