Not enough time for recovery: Coral bleaching occurs when stressful conditions result in the expulsion of the algal partner from the coral. Before anthropogenic climate warming, such events were relatively rare, allowing for recovery of the reef between events. Hughes et al. looked at 100 reefs globally and found that the average interval between bleaching events is now less than half what it was before. Such narrow recovery windows do not allow for full recovery. Furthermore, warming events such as El Niño are warmer than previously, as are general ocean conditions. Such changes are likely to make it more and more difficult for reefs to recover between stressful events. Science , this issue p. 80

Reef Repair: Coral reefs suffer mass mortality because of coral bleaching, disease, and tropical storms, but we know much more about when, where, and how rapidly these ecosystems have collapsed than we do about their recovery. Gilmour et al. (p. 69 ; see the Perspective by Polidoro and Carpenter ) studied a highly isolated coral reef before and after a climate-induced mass mortality event that killed 70 to 90% of the reef corals. The initial recovery of coral cover involved growth and survival of remnant colonies, which was followed by increases in larval recruitment. Thus, in the absence of chronic disturbance, even isolated reefs can recover from catastrophic disturbance.