What is the world's largest coral reef system?

The world's largest coral reef system is the Great Barrier Reef, off the coast of Queensland, Australia. It extends for more than 2,300 kilometres through the Coral Sea and consists of thousands of individual reefs and hundreds of islands.

The Great Barrier Reef is not one continuous wall of coral. It is a vast, connected ecosystem built by billions of tiny coral polyps. Its reefs developed over earlier submerged landscapes as sea levels changed, with the present reef structures dating back several thousand years. The system contains hundreds of coral species and supports fish, sharks, rays, sea turtles, sea snakes, seabirds, and marine mammals.

Australia established the Great Barrier Reef Marine Park in 1975, and UNESCO listed the reef as a World Heritage Site in 1981. The marine park regulates activities such as fishing, shipping, tourism, and research across a huge area.

A common mix-up is confusing the reef with the Great Barrier Reef Marine Park. The reef is the natural coral ecosystem; the marine park is the protected management area surrounding and covering much of it. Coral bleaching, warming seas, pollution, and crown-of-thorns starfish outbreaks remain major threats.