The Mekong, the world's most biodiverse river after the Amazon, meanders over 4,500 kilometres across Southeast Asia. From the Tibetan plateau, it runs through the Chinese province of Yunnan, Burma, Laos, Thailand, Cambodia, and Vietnam. For centuries, it has been the social and cultural lifeline of the region. The more than 1200 known species of fish in the Mekong have saved millions of people from starvation during droughts, floods, and the murderous Cambodian Pol Pot regime. This makes the river, with its entangled tributaries and arms, a highly complex entity, not only ecologically but also politically. It supports floating houses and markets, is a transport route, a fish reserve, the backbone of hygiene and tourism, and offers numerous opportunities to generate electricity. China has built 11 dams on the Mekong in recent years. Downstream, in Laos and Cambodia, numerous dams and barrages are also being built. The poorer countries want to capitalise on hydropower and sell the green electricity generated to China, Thailand, and Vietnam.

In South Vietnam, the Mekong River fans out into a wide delta before flowing into the South China Sea. About 20 million people live in the Mekong Delta, three-quarters of whom work in agriculture. Countless ditches, dams, irrigation canals, and sluices make the delta one of the most productive agricultural regions in the world. But the Mekong Delta is currently struggling with a combination of problems that are damaging rice quality. In recent years, the region has experienced severe droughts. The dams on the Mekong tributaries are the main cause of this, along with El Niño. For a country like Vietnam, traumatised by decades of war and famine, food security without intensive rice cultivation is unimaginable. In addition, the dams cut off the path of fish, threatening their conservation and community fisheries. Some fish migrate hundreds of kilometres to spawn. The dams could seal their fate. The area is also home to many other endangered species, such as monkeys, tigers, and Asian elephants.