Study finds ‘remarkable’ atoll shoreline resilience: unchanged over 51 years despite sea level rise

Aldabra Atoll [credit: NASA Earth Observatory / Wanmei Liang]

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Aldabra is the world’s second-largest coral atoll. Claims of such places being in danger of sinking under the waves any time soon, allegedly due to faraway industrial activities, may have been exaggerated.
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An international team led by University of Zurich and Seychelles Islands Foundation researchers highlight Aldabra Atoll’s resilience and its ability to maintain its shoreline despite the threats to reef island processes, says Phys.org.

They emphasize the key role of non-climate factors, such as sediment supply in driving changes to the shoreline. Additionally, they stress the importance of long-term monitoring and the critical role of Aldabra’s protection status in preserving its natural dynamics.

Low-lying islands are threatened by sea level rise due to global warming. Between 1993 and 2013, coastal areas within the Western Indian Ocean experienced a sea level rise of 2–3 mm per year.

Understanding how this rise affects the shoreline of Aldabra Atoll, a UNESCO World Heritage Site in Seychelles, is crucial for the management and protection of its unique ecosystem and species.

Aldabra’s shoreline is dynamic but does not show major loss overall
A new study led by scientists from the University of Zurich and the Seychelles Islands Foundation has illuminated the dynamic yet stable nature of Aldabra Atoll’s shoreline.

Recently published in Scientific Reports, this research tracked shoreline changes for 51 years using aerial and satellite images, providing the first comprehensive understanding of shoreline responses on raised atolls.

Despite rising sea levels and reduced sediment supply, Aldabra Atoll has successfully maintained its net shoreline and likely total land area. Findings show that 61% of the shoreline remained unchanged, while the areas that did change averaged approximately 25 cm per year—lower than the global average for atolls.

The lagoon shoreline underwent more rapid changes than the erosion-resistant ocean shoreline, particularly in areas exposed to wind and waves.
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Annabelle Constance from the Seychelles Islands Foundation, the lead author, stated, “Our findings are significant as they highlight Aldabra Atoll’s resilience and its ability to maintain its shoreline despite rising sea levels and climate change.”

She further emphasized, “Our research enhances understanding of reef island adjustment capacities in raised atolls and provides a benchmark for shoreline change rates for atolls, given the minimal human impact on Aldabra.”

Full article here.
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Image: Aldabra Atoll [credit: NASA Earth Observatory/ Wanmei Liang]