During 2020, mangrove die-back occurred on at least 11 islands in the Maldives which is the lowest elevated nation on Earth and where mangroves provide crucial shoreline protection. Here, we use remote sensing and data from wood and sediment cores from dead and living mangrove areas to test the hypothesis that sea level rise is driving mangrove loss. Mangrove health and areal cover were examined from 2014 - 2022 using Landsat satellite images (30 m resolution) and normalized difference vegetation index (NDVI). The relationship between mangrove health, sea level and precipitation was assessed by linear regression, which showed that mangrove die-back corresponds to an increase in sea level rise. Results from NDVI analysis revealed that mangrove health has decreased significantly since 2020, on all islands, resulting in the complete loss of mangroves in some islands. Affected areas are low-lying within the intertidal zone and dominated by the species Bruguiera cylindrica, which has a low tolerance to salinity and waterlogging. Wood cores were sampled for ¹⁴C dating and δ¹³C to calculate temporal changes in water use efficiency, combined with ITRAX elemental scanning to identify changes in water source and availability. Sediment cores were analysed using ²¹⁰Pb dating and δ¹³C to identify changes in sediment redox conditions. This research is crucial to the understanding of tipping points for mangrove ecosystems on low-lying islands under climate change and is essential to guide conservation and rehabilitation strategies.

Primary Presenter: Lucy Carruthers, Northumbria University (lucy2.carruthers@northumbria.ac.uk)

Authors:

Douglas Tait, Southern Cross University  (Douglas.Tait@scu.edu.au)

Christian Sanders, Southern Cross University   (Christian.Sanders@scu.edu.au)

Damien Maher, Southern Cross University  (Damien.Maher@scu.edu.au)

Vasile Ersek, Northumbria University  (vasile.ersek@northumbria.ac.uk)

Holly East, Northumbria University  (holly.east@northumbria.ac.uk)

Shaha Hashim, Maldives Resilient Reefs  (shaha@bluemarinefoundation.com)

Areesh Abdulla, Huvadhoo Aid  ()

James Sippo,   (James.Sippo@scu.edu.au)