Blue Carbon Additionality and Permanence in the coastal mangrove forests of the Mekong Delta, Viet Nam

The Mekong Delta is one of the largest deltas in the world, spanning approximately 55,000 km² and sharing approximately 50.2% of Vietnam’s mangrove ecosystems (90.8 km² km²; Tinh et al., 2022). Supporting ~18 million people, the Mekong Delta region faces many pressures, including land conversion for shrimp aquaculture, expanding urban centres, deforestation, and coastal erosion. In response to these challenges, mangrove forests in the Mekong Delta have been the focus of several restoration and conservation efforts in recent years, with 27.3  km² of coastal mangrove forests currently being restored and/or conserved under current forest management efforts.

The purpose of this study is to quantify how mangrove restoration in Ca Mau province, Viet Nam, delivers blue carbon additionality within mangrove ecosystems, particularly where land conversion for shrimp aquaculture has driven deforestation. Field sampling for total ecosystem carbon stocks across natural and restored forests, including integrated shrimp-mangrove aquaculture systems, reflecting one of the region's dominant land-use practices, was carried out by using standardized blue carbon protocols. Mangrove tree diameter, height and species, and downed dead wood were measured and recorded to estimate biomass and necromass carbon stocks. 397 soil samples were collected to estimate belowground soil carbon stocks. Preliminary results from two natural and two restored sites of different ages, show clear evidence of additionality in both aboveground and belowground carbon stores after restoration. However, a comparison of earth observation data between 2010 and 2024 allows us to provide a tentative estimate of carbon losses due to ongoing coastal erosion in these fringing mangrove forests.

These results highlight that efforts to restore mangrove forests in the Mekong Delta can deliver quantifiable blue carbon benefits, potentially underpinning new carbon crediting opportunities to help fund further mangrove restoration across the Mekong Delta. For restoration efforts to be effective in the long-term, careful consideration of ongoing habitat loss, increasingly driven by coastal erosion in response to anthropogenic sea-level rise, will be necessary.