What is the largest coral reef in the world?
Quick answer
The Great Barrier Reef, off the coast of Queensland, Australia, is the largest coral reef system in the world. It stretches about 2,300 km (1,400 miles) and is made up of around 2,900 individual reefs and 900 islands. It’s often called the largest structure built by living things.
Key facts
- Location
- Coral Sea, off Queensland, Australia
- Length
- About 2,300 km
- Marine park area
- About 344,400 km², larger than Italy
- UNESCO World Heritage
- Since 1981
What is a coral reef?
Corals look like rocks or plants, but they’re animals: colonies of tiny creatures called polyps. Each polyp builds a hard limestone skeleton. Over thousands of years, these skeletons pile up into reefs. Corals get much of their food and color from tiny algae living inside them.
Life on the reef
| Group | Approximate number of species |
|---|---|
| Hard corals | 400+ |
| Fish | 1,500+ |
| Mollusks | 4,000+ |
| Sea turtles | 6 of the world’s 7 species; see the largest sea turtle |
| Whales, dolphins and dugongs | 30+ species |
Coral bleaching
When water gets too warm, corals expel their algae and turn white, a process called bleaching. If the heat lasts too long, the corals can die. The Great Barrier Reef has suffered several mass bleaching events since 2016, linked to rising ocean temperatures. Other threats include crown-of-thorns starfish, pollution from farm runoff and cyclones.
Other large reefs
| Reef | Location |
|---|---|
| Great Barrier Reef | Australia |
| Mesoamerican Barrier Reef | Mexico, Belize, Guatemala, Honduras |
| New Caledonia Barrier Reef | South Pacific; see what language is spoken in New Caledonia |
| Florida Reef | United States |
Snorkeling and diving the reef
Cairns, Port Douglas and the Whitsunday Islands are popular gateways for snorkeling and diving. Choosing operators with eco-certification helps protect the reef.
Coral reefs show why the ocean is important and why biodiversity matters.
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