What is the largest coral reef system on Earth, home to thousands of marine species?

The largest coral reef system on Earth is the Great Barrier Reef, off the coast of Queensland, Australia. It stretches for about 2,300 kilometres through the Coral Sea and is made up of thousands of individual reefs and hundreds of islands.

The reef was built over immense periods by tiny coral animals called polyps. These animals secrete hard calcium-carbonate skeletons, creating the framework that supports an extraordinary range of life, including fish, sea turtles, sharks, rays, molluscs and seabirds. The Great Barrier Reef is also the world’s largest structure made by living organisms.

A common mix-up is confusing the Great Barrier Reef with the largest single coral colony or the longest coral reef. “Largest coral reef system” refers to the complete interconnected system, not one continuous wall of coral. It is also a UNESCO World Heritage site, recognised for its exceptional biological diversity and geological importance.