Low average shoreline change rate in 51 years on the raised Aldabra Atoll

Atolls face risks from rising sea levels and reduced sediment supply from coral reefs, leading to accelerated erosion. This study examines Aldabra, a raised atoll and UNESCO World Heritage Site in the Indian Ocean, tracking shoreline changes against a regional sea level rise of 2–3 mm per year. Using aerial and satellite images from 1960 and 2011, 85% of Aldabra’s shoreline was analyzed. Over 51 years, 61% of the shoreline remained unchanged, while 24% changed at a low average rate of 0.25 ± 0.36 m per year. Erosion and accretion rates were nearly balanced, with significant localized changes, such as a lagoon shoreline transforming into a mangrove habitat. Critical erosion occurred at turtle nesting sites and the research station. The lagoon shoreline experienced more rapid changes than the ocean-facing side. Despite these dynamics, Aldabra's overall shoreline and land area remained stable, similar to other Indo-Pacific atolls, highlighting its adaptive capacity. This research underscores the need to minimize local impacts on sediment availability to preserve the natural dynamics and adaptation potential of reef islands. Continuous shoreline monitoring is essential for developing timely adaptation strategies to conserve Aldabra's unique ecosystem.