Sea-level rise and extreme Indian Ocean Dipole explain mangrove dieback in the Maldives
Lucy Carruthers, Vasile Ersek, Damien T. Maher, Christian J. Sanders, Douglas R. Tait, Juliano Fonseca Soares, Matthew Floyd, Aminath Shaha Hashim, Stephanie B. Helber, Mark H. Garnett, Holly K. East, Jamie A. Johnson, Gheorghe Ponta, James Z. Sippo
Abstract
Abstract Mangrove forests enhance Small Island Developing States’ resilience to climate change, yet in 2020, a mangrove dieback impacted ~ 25% of mangrove-containing islands in the Maldives. Using remote sensing, dendrology and sediment geochemistry, we document a significant decrease in mangrove health post-2020 (NDVI: 0.75 ± 0.09) compared to pre-2020 (0.85 ± 0.04; P < 0.0001). Dead trees showed reduced stomatal conductance ( δ 13 C: − 26.21 ± 0.11 ‰) relative to living ones (− 27.66 ± 0.14 ‰), indicating salinity stress. Critically, sea-level rise (30.50 ± 23.30 mm/year) outpaced mangrove sediment accretion (6.40 ± 0.69 mm/year) five-fold between 2017 and 2020. We attribute this dieback to salinity stress driven by record-high sea levels in 2020, linked to an extreme positive Indian Ocean Dipole event. These findings reveal the vulnerability of mangrove ecosystems to rapid sea-level rise and highlights the urgent need for adaptive conservation strategies in Small Island Developing States.