Why are coral reefs dying around the world?

The answer

Coral bleaching occurs when ocean temperatures rise just 1-2 degrees Celsius above the normal summer maximum, causing corals to expel the symbiotic algae (zooxanthellae) that provide them with up to 90% of their energy and their vibrant color. Without these algae, the coral turns white and begins to starve. If temperatures remain elevated for prolonged periods, the coral dies. The Great Barrier Reef has experienced multiple mass bleaching events since 2016, and scientists estimate that the world has already lost about half of its coral reef cover since the 1950s.