Great Barrier Reef facts: size, wildlife and heritage

The Great Barrier Reef is not a single wall of coral. It is a managed marine park made up of thousands of separate reefs, and the Marine Park covers 344,400 square kilometres.¹ It was created in 1975 through the Great Barrier Reef Marine Park Act, and it takes in the world's largest coral reef ecosystem.^6,7 Anyone asking what the Great Barrier Reef is will get the most useful answer from that mix: a protected zone of ocean, reefs and islands rather than one object you can point to.

The Reef Authority describes the reef as about 10 per cent of the world's coral reef ecosystems and one of the best known and most complex natural systems on Earth.⁸ It is both a Marine Park and a World Heritage Area, and it draws millions of visitors each year who come to enjoy it above and below the water.⁹ Those two labels do different jobs for a traveler: the park is where the rules and the zoning apply, and the heritage listing is where the reef's global value is recognized.

Coral is the headline, though it is a small share of the whole. Coral reefs make up only about 7 per cent of the Marine Park, while the rest is a wide range of habitats from shallow seagrass and mangroves to deep ocean.¹⁰ Keep that in mind as you read the figures below. A statement about the reef can be true of one place and unremarkable at another, and the facts that help are the ones tied to a place you will actually visit.

Count the parts and the reef starts to look like a country. The Marine Park includes some 3,000 coral reefs, 600 continental islands, 300 coral cays and about 150 inshore mangrove islands.⁴ Across the wider World Heritage Area the Reef Authority counts 1050 islands and cays, the high islands and the sandy cays together with the mangrove islands that help the whole system function.²¹

These types behave differently, and a visitor meets them differently. The Reef Authority separates the continental, or high, islands from the coral cays, which are at various stages of formation, and from the mangrove islands inshore.⁴ A day boat from Cairns does not stop at any of these. It heads for the outer reef, where an operator describes a pontoon far enough from coastal rivers, streams and sandy beaches for clear ocean water, at approximately 45 km offshore.²⁶

The reef is also a record. The Reef Authority notes that its environmental history is written into the reef structure, and that old massive coral cores show climate conditions over many hundreds of years.²⁷ The part of the reef you see on a snorkel is a thin living layer on a structure that has been growing for a very long time, which is worth remembering the next time a guide points at an old coral head.

The reef was declared a World Heritage Area in 1981.⁵ The World Heritage Area covers 348,000 square kilometres, bigger than the United Kingdom, Holland and Switzerland combined, and about 99 per cent of it lies within the Marine Park.^24,36 The two names describe almost the same water, one by management and one by global recognition.

People are part of the listing. The reef is sea country for more than 70 Traditional Owner groups, whose connections to the marine environment go back more than 60,000 years.³⁷ That history is easy to overlook on a brochure page about snorkeling, and it is part of why the reef is more than a nature reserve. The cultural value sits next to the ecological one in the heritage record.

The economy is part of the story as well. A Deloitte study quoted by the Reef Authority values the reef at $95 billion across economic, social and cultural dimensions, and says it contributes $9 billion a year to the Australian economy and supports 77,000 full-time jobs.^25,38 Tourism is the largest contributor, at $7.9 billion a year.³⁹ Your ticket is one small piece of that total.