With a coastline stretching over 3000 kilometres and extensive aquatic resources, Vietnam is among the top 5 seafood export countries globally. The industry contributes to about 5% of the country’s Gross Domestic Product and 50% of the country’s marine fisheries are found in the Vietnamese Mekong Delta (VMD), making it a cornerstone of food supply.
Its long coastlines and low-lying coastal regions also mean that Vietnam is among the countries most exposed to coastal hazards intensified by climate change, which implies that the nation’s bustling seafood export industry is vulnerable—but how exactly?
A recent study led by Mr. Feng Yikang, a Research Associate at the Earth Observatory of Singapore working with the Tropical Rivers Group led by EOS Principal Investigator Edward Park and the Climate Transformation Programme, uncovered that the zone where the Mekong River meets the South China Sea, typically called a river plume, has shrunk since 2000. Published in the Journal of Hydrology, the study is the first long-term monitoring of the plume in the VMD and offers insights to its evolution due to human activities.
Members of the Tropical Rivers Group and co-authors of the study, from left to right: Dr. Dung Duc Tran, Mr. Feng Yikang, Asst. Prof. Jingyu Wang and Asst. Prof. Edward Park (Source: Yasmin Mohamed Basir/Earth Observatory of Singapore)
Mr. Feng and his team investigated the long-term dynamics of the Mekong plume over 1988–2022 based on Landsat satellite remote sensing and in-situ measurements of water level, discharge and suspended sediment concentration. Previous studies attempted to understand the sediment dynamics along the coastal zone of the VMD, but most were conducted at specific sectors or over just a few years. By looking at the evolution of the whole river plume over more than 30 years, the new study unravelled how the delta dynamics has changed in response to environmental stressors such as climate change.
A composite satellite image showing the overview of the delta and the plume. It is based on Landsat satellite images (1988–1999, January), processed using Google Earth Engine. (Source: Tropical Rivers Group/Earth Observatory of Singapore)
“Our study found that Mekong plume has been severely impacted since 2000, reducing by 63-83% compared to 1988-1999. This is a cause of concern because the plume provides nutrient-rich flow that sustains the ecology of the marine fisheries in the VMD,” said Mr. Feng.
“Our findings on the plume dynamics also suggest potential implications on the coastal ecosystems, especially on mangroves,” added Mr. Feng. This is because coastal mangroves are increasingly deprived of the sediments needed for their survival.
The research team also found that the decline of the Mekong plume correlates with the occurrence of less tropical cyclones. When cyclones strike land, large amounts of sediments are deposited into rivers. When cyclones move away from the Mekong, there are fewer landfalls, and less sediment supplied to the plume.
What does this mean for Singapore and the region?
These climate-driven changes are compounded by human activities such as dam activities, riverbed mining, and land use change, which intensified post-2000 and further deplete the sediment supply. Together, these environmental stressors support growing concerns that Vietnam’s rice bowl is shrinking, both in terms of landmass and its ability to support agricultural productivity, challenging the long-term regional food security.
By providing context to support more targeted coastal management, the team’s results draw attention to locations facing higher risk of sediment deprivation. By analysing associated stressors, the study can also be used to facilitate the development of strategies to address coastal degradation at its source. ____________________________________________________________________________________________________________________________________________
This study was supported by various grants from the Ministry of Education of Singapore (MOE) under its Academic Research Funds (AcRF) Tier 1 (RG142/22 and 2021-T1-001-056), Tier 2 (MOE-T2EP402A20-0001 and MOE-T2EP50222-0007), Tier 3 Climate Transformation Programme (MOE-MOET32022-0006), and NIE AcRF (RI 10/22 EP).