Coral Reef Recovery Trajectories

Abstract

Coral reef recovery following bleaching events -- the process by which coral cover, species richness, and three-dimensional structural complexity rebuild after thermal stress-induced mortality -- is the ecological process determining whether the world's most biodiverse marine ecosystems can persist through the Anthropocene climate transition. Recovery trajectories vary enormously across reef systems: some reefs recover substantially within 10-15 years of major bleaching; others remain in degraded, macroalgae-dominated states for decades. Identifying the ecological, oceanographic, and management conditions that predict recovery vs. persistent degradation is the most urgent applied question in coral reef science, because it determines where conservation investment will yield recovery and where climate mitigation is the only effective strategy. This study synthesises 247 coral reef monitoring time series from 84 reef systems in 28 countries, spanning 1998-2024 (covering three major global bleaching events: 1998, 2016, and 2020), to quantify recovery rates and identify their predictors. Mean coral cover recovery rate was 2.84 +- 1.47% cover/year across all reefs and bleaching events, reaching pre-bleaching cover in mean 9.4 +- 4.4 years when recovery occurred. Recovery to pre-bleaching cover was achieved by only 38.4% of monitored reefs within 15 years -- the majority remained in degraded states. Human modification index (fishing pressure; water quality) was the strongest local predictor of recovery (partial R2 = 0.54; p < 0.001), followed by thermal refuge availability (R2 = 0.38) and coral larval connectivity (R2 = 0.28). Reefs in marine protected areas with low fishing pressure showed 2.47x faster recovery than unprotected reefs, confirming that local management intervention substantially improves recovery prospects even under global climate change.