A global marine heat event raised ocean temperatures to dangerous levels for coral reefs around the world between 2014 and 2017. Now, scientists say they’ve quantified the number of corals that actually bleached and died during those years.
The new findings suggest around 51 percent of the world’s coral reefs suffered at least moderate bleaching, a phenomenon in which heat stress prompts corals to expel the colorful algae living inside them. Bleaching doesn’t kill the reefs outright — they can survive if cooler conditions return with enough time for them to recover — but it does increase their risk of dying.
The study, published Tuesday in the journal Nature Communications, also suggests that around 15 percent of the world’s reefs died between 2014 and 2017. The findings indicate that the global bleaching event — the third of its kind documented by humans — was the most severe on record.
But it could be surpassed by an ongoing fourth global bleaching event, scientists warn. Ocean temperatures have skyrocketed since 2023, and reefs around the world are once again suffering the consequences.
