15 Big Facts About the Great Barrier Reef

Australia’s biggest natural wonder is a huge draw for tourists and fish alike. Here’s everything you need to know about the world’s most famous reef.

1. The Great Barrier Reef is the largest organic structure on Earth.
2. Not as much of the reef is covered in coral as you might think.
3. The colossal reef system is larger than most countries.
4. Half of the Great Barrier Reef’s coral has disappeared since the mid-1980s.
5. Indigenous Australian peoples legally own tracts of the reef.
6. Four European explorers encountered the reef but failed to document its character.
7. Captain James Cook found the reef when his ship broke down on top of it.
8. A sunken ship rests beneath the reef.
9. It’s a breeding ground for sea turtles and birds.
10. 1600 species of fish call the reef home.
11. Its corals have mass spawning events during springtime full moons.
12. The Great Barrier Reef is the most densely populated ecosystem on Earth.
13. You can visit the reef using Google Street View.
14. The reef is a tourism dynamo.
15. The Great Barrier Reef is on the move.

The Great Barrier Reef is the largest organic structure on Earth.

The Great Barrier Reef is occasionally called the largest single organism on the planet. However, the reef is more accurately identified as an amalgam of distinct organisms. Living building blocks called coral polyps create (through calcium secretions) upwards of 3000 individual coral reefs, which along with more than 900 islands and cays make up the famed ecosystem.

Not as much of the reef is covered in coral as you might think.

The name may be misleading you. Within the Great Barrier Reef Marine Park, coral covers only about 6 or 7 percent of the territory. 

The colossal reef system is larger than most countries.

By spanning over 135,000 square miles, the Great Barrier Reef eclipses the sizes of over 100 countries. Ranked among the world’s nations, the reef system would place 63rd, just between Germany (boasting an area of 138,000 square miles) and the Republic of the Congo (132,000 square miles). Furthermore, the Great Barrier Reef is larger than most American states, outdone only by Alaska, Texas, California, and Montana. 

Half of the Great Barrier Reef’s coral has disappeared since the mid-1980s.

Though the Great Barrier Reef’s coral formations still inspire awe, they are only about half as numerous as they were a mere 40 years ago. In 2012, a study by the Australian Institute of Marine Science concluded that 50 percent of the reef’s coral had deteriorated since 1985 due to damage from storms, predatory crown-of-thorns starfish, and coral bleaching. 

Indigenous Australian peoples legally own tracts of the reef.

Rich with historical meaning and natural resources, the Great Barrier Reef is a site of great cultural and spiritual significance to Aboriginal Australians and Torres Strait Islanders. More than 70 subgroups with connections to areas of the reef are recognized by the Australian government as Traditional Owners and are compensated for the nation’s use of the marine property. 

Four European explorers encountered the reef but failed to document its character.

When European countries began sending voyagers through Oceania, they came into contact with—but, oddly enough, didn’t take much notice of—Australia’s Queensland coast and the Great Barrier Reef. Portuguese nobleman Cristóvão de Mendonça may have kicked off this trend when his supposed 1522 encounter with the reef sparked so little interest that he didn’t even bother to document his discovery. Dutch navigator Willem Janszoon and Galician seaman Luís Vaz de Torres each happened upon the reef between 1605 and 1606, likewise failing to commit their find to official record. The very first documentation of European interaction with the Great Barrier Reef came from French admiral Louis Antoine de Bougainville’s 1768 exploration of the region. However, even Bougainville would not focus on the natural wonder; his crew was short on supplies and turned immediately to seek the security of the nearby South Asian coast. 

Captain James Cook found the reef when his ship broke down on top of it.

Today, English adventurer Captain James Cook is credited with being the first Westerner to properly encounter the Great Barrier Reef. However, Cook’s run-in with the reef was not the product of ambitious exploration, but rather the result of an accident. In 1770, Cook’s ship Endeavour collided with the top of the reef during pursuit of an alleged continent near New Zealand, which he was charged with claiming for England. The collision resulted in substantial damages to Cook’s vessel, forced him to dock for repairs. This distraction may have prevented the captain from appreciating the great majesty of his find, though he managed to make exceptionally accurate charts of the region. 

A sunken ship rests beneath the reef.

While the Endeavour escaped the reef’s clutches with reparable damages, the SS Yongala was not so fortunate. The passenger ship was undone by a cyclone off Australia’s eastern coast in 1911, sinking to the bottom of the Pacific about 48 nautical miles away from the Queensland city of Townsville. Today, the 350-foot-long ship remains within the perimeter of Great Barrier Reef Marine Park and provides a home to hundreds of diverse fish species. 

It’s a breeding ground for sea turtles and birds.

The Great Barrier Reef is not just beautiful; it functions as a traditional breeding ground for many animal species. Among those for which the reef provides critical shelter and resources are four species of sea turtle—green, flatback, hawksbill, and loggerhead—with leatherback and olive ridley turtles also calling it home. That's in addition to 1.5 million birds comprising 22 different species.

1600 species of fish call the reef home.

The reef offers a home to an astronomical number of fish species, including damselfish, tuskfish, wrasses (the most common inhabitants), angelfish, blennies, butterfly fish, chimeras, clownfish, coral trout, cowfish, gobies, hawkfish, pipefish, potato cod, pufferfish, rays, scorpion fish, seahorses, sea perch, sharks, snapper, surgeonfish, and triggerfish. It is estimated that approximately 10 percent of the world’s fish species live within the Great Barrier Reef. 

Its corals have mass spawning events during springtime full moons.

No creatures take greater advantage of the Great Barrier Reef’s amorous ambiance than the corals themselves. Once every year, the passing of a springtime full moon invites the reef’s coral population to participate in a mass spawning that has been called the greatest unified movement of reproduction on the planet. Triggered by genes devoted to detecting moonlight, corals spend the week releasing sperm and eggs (and getting an assist from scientists trained in “coral IVF”) to carry on their species’ near-motionless legacy. 

The Great Barrier Reef is the most densely populated ecosystem on Earth.

Fish aren’t the only animals to occupy the reef in huge numbers. The realm features approximately 400 species of corals, 300 species of sea squirts, and nearly 5000 species of mollusks. Occupying the coastline are 22 species of seabirds, 32 species of shorebirds, and more than 150 additional bird species. Along with six species of sea turtles, the reef houses 17 species of sea snake, seven species of frogs, and the occasional saltwater crocodile. What’s more, the Great Barrier Reef boasts 30 cetacean species (whales, dolphins, and porpoises), the subantarctic fur seal, and one of the largest populations of dugongs on Earth. 

You can visit the reef using Google Street View.

In 2014, Google Street View, which lets users observe photographs of their (usually landlocked) destinations, updated its database with underwater images of the Great Barrier Reef. 

The reef is a tourism dynamo.

The Great Barrier Reef creates about billions in tourist spending every year, a huge shot in the arm for the area adjacent to the reef.

The Great Barrier Reef is on the move.

In recent years, scientists have noticed southward migration of many fish and corals that previously stayed within the confines of the Great Barrier Reef. As water temperatures rise throughout Oceania, reef dwellers set their courses for the more hospitable New South Wales coast. Not only is this climatic change disruptive to the harmony of the reef itself, it impacts the New South Wales shorelines’ native communities of algae and seaweed—species that require even cooler waters to sustain life.

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A version of this story was published in 2015; it has been updated for 2025.