Coral reef state influences resilience to acute climate-mediated disturbances

Aim: The aim of this study was to understand the interplay between resistance and recovery on coral reefs, and to investigate dependence on pre- and post-disturbance states, to inform generalizable reef resilience theory across large spatial and temporal scales. Location: Tropical coral reefs globally. Time Period: 1966–2017. Major Taxa Studied: Scleractinian hard corals. Methods: We conducted a literature search to compile a global data set of total coral cover before and after acute storms, temperature stress and coastal run-off from flooding events. We used meta-regression to identify variables that explained significant variation in disturbance impact, including disturbance type, year, depth and pre-disturbance coral cover. We further investigated the influence of these same variables, as well as post-disturbance coral cover and disturbance impact, on recovery rate. We examined the shape of recovery, assigning qualitatively distinct, ecologically relevant, population growth trajectories: linear, logistic, logarithmic (decelerating) and a second-order quadratic (accelerating). Results: We analysed 427 disturbance impacts and 117 recovery trajectories. Accelerating and logistic were the most common recovery shapes, underscoring non-linearities and recovery lags. A complex but meaningful relationship between disturbance impact, the state of a reef pre- and post-disturbance, and recovery rate was identified. Fastest recovery rates were predicted for intermediate to large disturbance impacts, but a decline in this rate was predicted when more than ~75% of pre-disturbance cover was lost. We identified a shifting baseline, with declines in both pre- and post-disturbance coral cover over the 50-year study period. Main Conclusions: We break down the complexities of coral resilience, showing interplay between resistance and recovery, as well as dependence on both pre- and post-disturbance states, alongside documenting a chronic decline in these states. This has implications for predicting coral reef futures and implementing actions to enhance resilience.