Coral recovery rates at equal cover on 103 Great Barrier Reef monitoring reefs fell in 1992–2010, but in 2011–2026 they returned to 1990s levels and did not follow the extended decline

Ortiz et al. (2018) reported that coral recovery rates on the Great Barrier Reef fell by 84% from 1992 to 2010. We did a test of whether this decline continued after 2010. We used AIMS Long-Term Monitoring Program photo-transect data (103 reefs, 1992–2026), the AIMS disturbance log for each reef, and AIMS manta-tow reef estimates (199 reefs, 1986–2026). We used the recovery rate of Ortiz et al.: IGR = ln((C1+5)/(C0+5))/Δt. We calculated it for consecutive surveys with no recorded disturbance, and we adjusted for the starting cover. In 1992–2010 the rate fell by 50% (0.102 to 0.051/yr at 27% cover; slope −0.0029/yr per yr, 95% CI −0.0044 to −0.0014). A line fitted to the 1992–2010 intervals and extended after 2010 was too low for the 561 later intervals: the mean observed-minus-predicted IGR was +0.078/yr (reef bootstrap 95% CI 0.038 to 0.121). The adjusted mean rates were 0.085 (1992–2000), 0.063 (2001–2010), 0.102 (2011–2018) and 0.083/yr (2019–2026). The 2011–2026 rate was the same as the 1992–2000 rate. Acroporidae corals caused both the decline and the recovery; other hard corals had no trend. Manta tows gave the same result (+0.093/yr, CI 0.069 to 0.119). All 13 planned sensitivity analyses gave the same direction, including a quantile test that does not use disturbance flags: 55% of post-2010 intervals were above the extended 75% quantile line, but 25% were expected. Limitations: AIMS records disturbances partly from observed coral loss, so the selection of undisturbed intervals depends partly on the outcome. We used reef means and AIMS families, not the transect breaks and six coral groups of Ortiz et al. The result is only about the recovery rate between disturbances. It is not about how often disturbances occur or how much coral they kill. The package contains code, aggregate results and figures. It does not contain AIMS data (CC BY-NC 3.0 AU); the code downloads the data again.

Great Barrier Reef · coral recovery · resilience · AIMS LTMP · Acropora · instantaneous growth rate · replication · out-of-sample test · coral reef monitoring · disturbance