The fourth global coral bleaching event, announced this week, is an urgent wake-up call to the world.
What happened last summer? Widespread mass bleaching is new for coral reefs. The first global bleaching event was in 1998. On the Great Barrier Reef, large areas were exposed to record-breaking heat stress over its summer . Prevalent bleaching was observed on three-quarters of surveyed coral reefs in shallow water.
Why are coral reefs so important? Coral reefs are vital for ocean health. They also provide food, income and coastal protection from storms and floods for an estimated 500 million people. They cover less than 1% of the seafloor but support at least 25% of marine species. Some coral deaths are immediate. Some colonies recover, while others succumb after the ocean heat subsides. Complex local and species-specific differences are typical for the responses of corals to heat stress and their recovery after an event.