Echoes of the past, warnings for the future: seven decades (1956–2025) of coral reef trajectories under repeated bleaching and local pressures in Addu Atoll, Maldives

The interaction between climate-driven thermal disturbances and local anthropogenic pressures increasingly shapes coral reef trajectories. Addu Atoll (Maldives) provides a rare opportunity to assess long-term reef change, as data from multiple historical expeditions and monitoring programmes allow seven decades (1956–2025) of change to be reconstructed. We integrated heterogeneous historical records with standardised surveys conducted in 2025 across nine reef sites, assessing temporal trends in live hard coral cover at 5 m and 10 m depth, differences associated with reef type and local human pressures, and shifts in coral community composition. Reefs at 5 m depth experienced a pronounced decline following the 1998 bleaching event, gradual recovery, a further reduction after 2016, and a strong increase by 2025, reaching levels comparable to historical conditions despite the 2024 global bleaching event. Live hard coral cover at 10 m depth was more stable throughout. Lagoon- versus ocean-facing reefs showed no consistent differences in live hard coral cover, whereas reefs under high human pressure displayed clear signs of degradation, including reduced cover and shifts towards simplified assemblages. Community change was strongly site-specific, ranging from increases in branching and tabular framework-building corals at less impacted sites to dominance by massive or foliose forms at the most disturbed locations. No coral-to-algal phase shift was detected; macroalgal cover remained low and never exceeded live hard coral cover. Addu reefs appear capable of recovering from repeated bleaching events, though trajectories depend on local environmental quality. Limiting chronic anthropogenic stressors is a key management priority for maintaining coral dominance and structural complexity under continued ocean warming.