This article was featured in Eurofish Magazine 2 2026.
Between 2014 and 2017, the world’s coral reefs endured the most damaging bleaching event record to date. A study published in Nature Communications, drawing on data from over 15,000 reef surveys worldwide, estimates that more than half of all coral reefs experienced moderate or greater bleaching during this period, while 15% suffered significant coral mortality. These figures surpass both previous recorded global bleaching events in 1998 and 2010.
The event, driven by marine heatwaves associated with a strong El Niño, was also the first to last beyond a single year, with heat stress persisting across three consecutive bleaching seasons. Bleaching sensitivity varied across ocean basins, with Caribbean and Atlantic reefs being more sensitive to heat stress than those in the Asia-Pacific, though the latter faced some of the most intense heat exposure overall.
The findings point to an accelerating pattern. With decreasing recovery time between successive events, many reefs are now caught in damaging cycles that may be quietly eroding their species diversity even when coral cover appears to be recovering. The heat stress thresholds recorded during this event were severe enough to prompt NOAA to introduce new, more extreme bleaching alert categories, which are already being applied during the ongoing fourth global coral bleaching event.
