Saltwater is advancing deeper into Vietnam's Mekong Delta, threatening a region that has long underpinned the country's status as one of the world's leading rice exporters, according to reporting by UN News. Rising sea levels, reduced freshwater flows and upstream dam construction are together reshaping the conditions that generations of farmers have depended on — while El Niño threatens to compound the strain further.
Vietnamese authorities warned this summer that El Niño could bring prolonged heat, reduced rainfall and worsening saltwater intrusion, potentially threatening hundreds of thousands of acres of rice in the delta. During the dry season, salinity has already been moving upriver, prompting authorities to step up measures to protect freshwater supplies and to call for longer-term action on saltwater intrusion, subsidence and erosion.
A key driver of the delta's vulnerability is a sharp decline in sediment carried down the Mekong. Dams constructed upstream have trapped much of this material; according to a 2021 scientific study, sediment reaching the delta has fallen from roughly 143 million metric tons two decades ago to an estimated 32 million tons. Jack O'Connor, a marine ecologist at the United Nations University's Institute for Environment and Human Security in Bonn, explains that sediment normally settles along the coast and is trapped by wetlands and mangrove forests, allowing the ground to rise — a natural buffer against sea level rise. Without it, that defense erodes.
The resulting trade-offs are stark. Authorities monitoring salinity sometimes close sluice gates when river water grows too salty for rice irrigation. But O'Connor notes farmers face a harder calculation: "They're worried about the salt on their crops," he said, "but they're even more worried about the fact that if they don't have any water, there's no crop."
Some farmers are adapting by working with saltwater rather than against it. In An Giang Province, rice-shrimp farming — alternating rice cultivation in fresher conditions with shrimp, which tolerate brackish water, when salinity rises — now covers more than 100,000 hectares of saltwater-affected land, with farmers increasingly adopting organic methods using fewer chemical fertilizers and pesticides.
Research by O'Connor and colleagues on organic rice cultivation found measurable ecological benefits: organically farmed plots supported markedly greater biodiversity, including more abundant dragonflies, spiders and other natural predators, as well as fish and crabs that provided farmers with food or additional income. However, O'Connor's team also found that benefits had limits — water moves freely across the delta, linking one farm to the next, meaning individual adaptation has boundaries.
This article is based on a primary source and has undergone editorial review prior to publication.
