Chinese companies are building infrastructure and dams along the vast river that runs through five Southeast Asian countries before emptying into the South China Sea.
Without that water, the world's largest inland fishery, which produces as much as a quarter of global freshwater catch, would be in danger. The livelihoods of tens of millions of people living in the lower Mekong would be as well, because of the loss of water, fish and sediment that helps produce the fertile soil and abundant crop — especially rice — they depend on.