What is the world’s largest living structure, formed by organisms, according to descriptions of the Great Barrier Reef?

The Great Barrier Reef is widely described as the world’s largest living structure, formed by billions of tiny coral organisms.

Individual reef-building corals are animals called polyps. Each polyp secretes a hard skeleton of calcium carbonate, and colonies grow as generations of polyps build on the remains of earlier ones. Across thousands of reefs, these biological constructions create the enormous Great Barrier Reef ecosystem.

The phrase “largest living structure” is a popular description, but it does not mean that the reef is a single organism or one continuous object. It is a connected system of living coral communities, dead limestone frameworks, islands, lagoons and surrounding habitats. Its scale can be seen from space, although the whole reef is not a single solid band.

The Great Barrier Reef is also described as the largest coral reef system in the world. These phrases emphasize different ideas: “living structure” highlights its biological construction, while “reef system” emphasizes the thousands of separate formations that make up the whole.