Reefs have been battered by cyclones and starfish that eat coral, but heat stress driven by climate change is the main cause of damage.

Australia’s Great Barrier Reef suffered the worst coral bleaching on record. Both the northern and southern branches of the reef have been battered lately by tropical storms and the encroachment of invasive coral-eating crown-of-thorns starfish, but heat stress driven by warming oceans is the primary cause, scientists told the BBC.

Australia's Great Barrier Reef, the planet's largest living structure and a jewel of the natural world, has suffered the steepest coral cover collapse since records began almost four decades ago. Scientists warn that without urgent action,