The impact of climate change on the natural resources of coral reef islands in the Maldives

Carruthers, Lucy (2024) The impact of climate change on the natural resources of coral reef islands in the Maldives. Doctoral thesis, Northumbria University.

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Abstract

The protection and sustainable use of natural resources are crucial goals in the UN Sustainable Development Agenda 2030. However, climate change is threatening their resilience, particularly for reef islands in the Maldives. By investigating island erosion, groundwater quality, and mangrove dieback, this thesis addresses critical knowledge gaps and gains insights into the future trajectories of island communities under climate change.

Shoreline change analysis was performed on 49 islands in Huvadhoo Atoll from 1969 - 2019. Sea level rose 4.24 mm/year, yet 53% of islands accreted (22% were stable and 25% eroded). Rates of change were used to model shifts in lens volume in 2030, 2050 and 2100 in response to changes in recharge. Lens volume was substantially impacted by changes in shoreline compared to recharge. Accretion and erosion led to large increases (up to 65.05%) and decreases (up to -50.4%) in lens volume.

Groundwater quality was examined on six islands to understand the implications of sea level rise. Despite sampling during the dry season, three islands had potable groundwater, and wider atoll rim islands (> 500 m) displayed lower salinity (0.62 ± 0.68 PSU). Transporting groundwater from these islands to nearby inhabited ones could replace the demand for bottled water 4.2 and 2.9 times greater than the local population in Huvadhoo and Laamu Atoll, respectively.

Finally, remote sensing and dendrogeochemistry enabled investigations into the 2020 mangrove dieback which coincided with record high sea level. As sea level increased, Normalized Difference Vegetation Index decreased. δ13C analysis of mangrove wood revealed increased salinity in dead (-26.21 ± 0.11 ‰) trees compared to living (-27.66 ± 0.14 ‰) ones. Between 2017 - 2020, mangrove sediment accretion rates were 6.40 ± 0.69 mm/year while sea level was 4.8 times higher. A 2019 Indian Ocean Dipole event-caused extreme increases in sea level, triggering the dieback.

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