For hundreds of millions of years, coral reefs have supported life in our oceans. Although they cover less than 1% of the ocean floor, they provide habitat for at least 25% of all marine species. They also support people around the world by sustaining fisheries and tourism, providing food and livelihoods, and helping protect coastlines from waves and storms.

But coral reefs are under increasing pressure. Pollution, overfishing, coastal development, physical damage, and increasingly warm ocean temperatures can all affect reef health. One of the most visible signs that a coral reef is under stress is coral bleaching.

This September, in recognition of Coral Bleaching Awareness Month, we’re taking a closer look at what happens when corals bleach, why bleaching matters, and what scientists around the world are doing to better understand, protect, and restore coral reefs.