A rapidly closing window for coral persistence under global warming

Coral reefs around the world are increasingly threatened by marine heatwaves causing widespread coral bleaching and mortality. Global analyses of projected heatwaves can inform decision-making, but forecasting the interactions between disturbance refugia, coral life histories and capacity to adapt is key for guiding strategic management of coral persistence. Here, we simulate coral eco-evolutionary dynamics across 3800 reefs of Australia’s Great Barrier Reef under current climate projections. We project a rapid coral decline by mid-century under all emission scenarios, with further decline under the most likely warming trajectory. However, recovery is possible this century if warming remains below 2 °C, allowing thermal adaptation to keep pace. Our simulations show that resilient reefs are primarily in bleaching refugia, which also support a greater diversity of thermal phenotypes. While cool-adapted corals disperse to warm spots, we found no evidence of ‘gene swamping’ undermining thermal adaptation. Our findings highlight that management opportunities exist to promote adaptation in thermal refugia and warm spots, but emphasize that curbing global warming by 2050 is crucial for coral persistence. Global warming is causing widespread coral mortality through bleaching. Here, simulations of coral eco-evolutionary dynamics forecast strong population declines in the 21st century. Coral reefs may collapse by 2100, unless global warming is limited to 2 °C, enabling corals to adapt and persist.