Risk classification of low-lying coral reef islands and their exposure to climate threats

Thomas E Fellowes; Ana Vila-Concejo; Maria Byrne; Eleanor Bruce; Elaine Baker

doi:10.1016/j.scitotenv.2023.168787

Risk classification of low-lying coral reef islands and their exposure to climate threats

Sci Total Environ. 2024 Feb 20:912:168787. doi: 10.1016/j.scitotenv.2023.168787. Epub 2023 Nov 28.

Authors

Thomas E Fellowes¹, Ana Vila-Concejo², Maria Byrne³, Eleanor Bruce², Elaine Baker⁴

Affiliations

¹ Geocoastal Research Group, School of Geosciences, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia; Marine Studies Institute, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: thomas.fellowes@sydney.edu.au.
² Geocoastal Research Group, School of Geosciences, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia; Marine Studies Institute, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia.
³ Marine Studies Institute, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia; School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia.
⁴ Marine Studies Institute, Faculty of Science, The University of Sydney, Sydney, NSW 2006, Australia; UNEP/GRID-Arendal, The University of Sydney, Sydney, NSW 2006, Australia.

PMID: 38029987
DOI: 10.1016/j.scitotenv.2023.168787

Abstract

The bio-physical responses of low-lying coral islands to climate change are of concern. These islands exist across a broad range of bio-physical conditions, and vulnerabilities to rising and warming seas, ocean acidification and increased storminess. We propose a risk-based classification that scores 6 island eco-morphometric attributes and 6 bio-physical ocean/climate conditions from recent open-access data, to assign islands with respect to 5 risk classes (Very Low, Low, Moderate, High and Very High). The potential responses of 56 coral islands in Australia's jurisdiction (Coral Sea, NW Shelf and NE Indian Ocean) to climate change is considered with respect to their bio-physical attributes and eco-morphometrics. None of the islands were classed as Very Low risk, while 8 were classed as Low (14.3 %), 34 were Moderate (60.7 %), 11 were High (19.6 %), and 3 were Very High (5.4 %). Islands in the Very High risk class (located on the NW Shelf) are most vulnerable due to their small size (mean 10 Ha), low elevation (mean 2.6 m MSL), angular/elongated shape, unvegetated state, below average pH (mean 8.05), above average rates of sea-level rise (SLR; mean 4.6 mm/yr), isolation from other islands, and frequent tropical storms and marine heatwaves. In contrast, islands in the Low (and Very Low) risk class are less vulnerable due to their large size (mean 127 Ha), high elevation (mean 8.5 m MSL), sub-angular/round shape, vegetated state, near average pH (mean 8.06), near average SLR rates (mean 3.9 mm/yr), proximity to adjacent islands, and infrequent cyclones and marine heatwaves. Our method provides a risk matrix to assess coral island vulnerability to current climate change related risks and supports future research on the impacts of projected climate change scenarios. Findings have implications for communities living on coral islands, associated ecosystem services and coastal States that base their legal maritime zones on these islands.

Keywords: Climate change; Coastal management; Coastal vulnerability; Island stability; Maritime zones; Risk matrix.

MeSH terms

Animals
Anthozoa*
Climate Change
Coral Reefs*
Ecosystem
Hydrogen-Ion Concentration
Indian Ocean
Islands
Seawater