Sea-level rise and extreme Indian Ocean Dipole explain mangrove dieback in the Maldives

Lucy Carruthers; Vasile Ersek; Damien Maher; Christian Sanders; Douglas Tait; Juliano Soares; Matthew Floyd; Aminath Shaha Hashim; Stephanie Helber; Mark Garnett; Holly East; Jamie A Johnson; Gheorghe Ponta; James Z Sippo

doi:10.1038/s41598-024-73776-z

Sea-level rise and extreme Indian Ocean Dipole explain mangrove dieback in the Maldives

Sci Rep. 2024 Nov 12;14(1):27012. doi: 10.1038/s41598-024-73776-z.

Authors

Lucy Carruthers^{1

2}, Vasile Ersek³, Damien Maher⁴, Christian Sanders⁵, Douglas Tait⁴, Juliano Soares^{5

6}, Matthew Floyd⁷, Aminath Shaha Hashim⁸, Stephanie Helber⁷, Mark Garnett⁹, Holly East⁷, Jamie A Johnson⁷, Gheorghe Ponta¹⁰, James Z Sippo⁴

Affiliations

¹ Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK. [email protected].
² Department of Coastal Studies, Coastal Studies Institute, East Carolina University, Wanchese, NC, 27981, USA. [email protected].
³ Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK. [email protected].
⁴ Faculty of Science and Engineering, Southern Cross University, Lismore, 2480, Australia.
⁵ National Marine Science Centre, Southern Cross University, Coffs Harbour, 2450, Australia.
⁶ Universidade Federal Fluminense, Niterói, 24.020-141, Brazil.
⁷ Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK.
⁸ Maldives Resilient Reefs, Blue Marine Foundation, 20285, Malé, Maldives.
⁹ NEIF Radiocarbon Laboratory, Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF, UK.
¹⁰ Geological Survey of Alabama, Groundwater Assessment Program, Tuscaloosa, 35401, USA.

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 (δ¹³C: - 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.