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Great Barrier Reef
The largest living structure on Earth, a 2,300-kilometre coral system off Australia
The Great Barrier Reef is the largest living structure on the planet, a sprawling mosaic of coral stretching over 2,300 kilometres along the northeastern coast of Australia, so vast it is visible from space. Built by countless tiny coral polyps over millions of years, it is not a single reef but a complex of more than 2,900 individual reefs and some 900 islands and cays, covering an area larger than Italy. Beneath the turquoise surface lies one of the richest concentrations of life anywhere in the ocean.
The reef runs from the tip of Cape York southward to near Bundaberg, fringing the Coral Sea in the warm, shallow waters of the continental shelf. It shelters a staggering diversity of life: more than 1,500 species of fish, over 400 kinds of hard coral, six of the world's seven sea turtle species, dugongs, reef sharks, and migrating humpback whales. Yet this living system is acutely vulnerable. Rising sea temperatures have driven repeated mass bleaching events in recent years, alongside pressures from cyclones, coral-eating starfish, and runoff from the land.
Aboriginal and Torres Strait Islander peoples have fished and navigated these waters for tens of thousands of years, and their connection to the reef endures in story and custom. The reef nearly wrecked the explorer James Cook's Endeavour in 1770. Declared a marine park in 1975 and a UNESCO World Heritage Site in 1981, it draws millions of visitors and underpins a major tourism economy, even as scientists and managers race to protect it from the warming seas that threaten its survival.