Great Barrier Reef

A living structure visible from space

The Great Barrier Reef is a huge 'underwater city' built by tiny coral animals over thousands of years — 2,300 km long! You can see it from space. 1,500 species of colourful fish, turtles and sharks live on the reef. Corals are living creatures — if the water gets too warm they turn white and can die. That's why the reef needs protecting.

The Great Barrier Reef stretches 2,300 km along Australia's north-east coast, made of 2,900 individual reefs and 900 islands covering 344,000 km² — the largest structure built by living organisms. The present reef is about 8,000 years old (post-Ice Age), but its foundations are 500,000 years old. Coral polyps live in symbiosis with zooxanthellae algae, which give them colour and food; when water warms by 1–2 °C the polyps expel the algae and bleach. Mass bleaching occurred in 1998, 2002, 2016, 2017, 2020, 2022 and 2024; half the coral has been lost since 1995. It has 1,500 fish species, 400 corals, 4,000 molluscs and 6 species of sea turtle. A UNESCO site (1981), it draws 2 million tourists and 6 billion dollars a year.

Fun facts

• The reef is so big it can be seen from the International Space Station.
• Coral isn't a plant — it's an animal! Each one is like a tiny jellyfish.
• Once a year, on a full-moon night, all the reef's corals 'bloom' (spawn) at the same time.