Australian authorities say the Great Barrier Reef has experienced its greatest annual loss of live coral in four decades.

Australia’s Great Barrier Reef — a cornerstone of marine biodiversity and a symbol of natural wonder — is experiencing the worst coral loss ever recorded, according to a new report from the Australian Institute of Marine Science (AIMS).

The Great Barrier Reef is reeling from its largest coral loss yet, driven in part by extreme weather. The dramatic decline is a warning light, telling us in no uncertain terms, that our world’s reefs are in trouble.