Great Barrier Reef

The Great Barrier Reef is the largest coral reef system in the world, stretching about 2,300 kilometres along the coast of Queensland in north-eastern Australia. It was inscribed on the World Heritage List in 1981, which recognises places judged to be of outstanding value to all humanity. Rather than a single wall of coral, it is a mosaic of roughly 2,900 individual reefs and about 900 islands, with sand cays, mangrove shores and deep channels in between.

Its value lies as much in its variety as its size. The reef supports an enormous range of marine life, from corals and turtles to dugongs, sharks and migrating whales, and it is also home to cultures that have known these waters for far longer than anyone has written about them. Visiting responsibly matters here, because the reef is under real pressure from warming seas.

The reef as it stands today is geologically young. During the last ice age, sea level was far lower and the continental shelf off Queensland was dry land. As the ice melted and the sea rose, from roughly 20,000 years ago, coral larvae settled on the flooded shelf and began to build the living reef, much of which is only around 8,000 years old. Older reef structures lie beneath it. The coral itself is built by colonies of tiny animals called polyps, each of which secretes a limestone skeleton, and over generations those skeletons accumulate into the structures visible today. Reefs here take several forms: fringing reefs hug the coast and islands, ribbon reefs form long narrow barriers along the outer edge, and platform reefs rise as isolated patches on the shelf.

Aboriginal and Torres Strait Islander peoples have lived beside, and used, these waters for tens of thousands of years, and more than 70 Traditional Owner groups have connections to the reef. Their sea country is recorded in stories, in fish traps and in practice. European charting began in the 18th century: in 1770 James Cook's ship Endeavour struck a reef near present-day Cooktown and was badly damaged, an event that shaped the early navigation of the passage.

Protection came in stages. The Australian parliament passed the Great Barrier Reef Marine Park Act in 1975, creating a marine park managed by a dedicated authority. The park was inscribed in 1981, and a major rezoning in 2004 placed about a third of it in no-take areas, where fishing is not allowed. Today the greatest threat is climate change.

The reef was inscribed under all four natural criteria, a rare distinction. Under criterion (vii), it contains superlative natural phenomena and areas of exceptional beauty, from turquoise cays to reef walls seen from above. Under criterion (viii), it is an outstanding record of the Earth's history, because the reef's structure and the shelf beneath it show how sea-level change shaped the coast.

Under criterion (ix), it is an outstanding example of ongoing ecological and biological processes, with coral, algae and fish communities that are still evolving. Under criterion (x), it holds exceptional biodiversity, including many threatened species. Few places meet all four, and the reef's listing reflects that it is valued both as a natural wonder and as a scientific record of how marine ecosystems respond to a changing sea.

No other coral reef system is comparable in scale: it is the largest in the world, and one of the few that can be seen as a single connected landscape from the air.

The reef lies on a continental shelf of shallow water, between the Queensland coast and the open Coral Sea, and covers about 348,000 square kilometres. In the north the shelf is narrow and the outer reef is close to shore; in the south it is wide, and the outer reef lies more than 200 kilometres out.

Above the water, sandy cays and continental islands, some with rainforest, break the horizon. Below it, the habitat changes with depth and exposure, from sheltered lagoons with seagrass to reef slopes lined with coral. The climate is tropical, with a hot, wet season from November to April and a cooler, drier season from May to October, and tropical cyclones are most likely between January and March.

Most visits are a day on a boat. You travel between one and two and a half hours each way, spend three to four hours at one or two reefs, and are fed, briefed and generally kept moving. Snorkelling is the easiest option and requires only basic swimming skills; certified divers can go deeper, and introductory dives are offered.

Expect crowds at the best-known pontoons and quieter water at smaller operators. The reef varies: some sites are dazzling, with healthy coral and fish in the hundreds, while others show the pale skeletons of bleached coral. Ask your operator which reef they are going to and how it is currently faring.

Seasickness is common on the crossing, so take medication before you board, not after. Sun is intense even on overcast days. Between about November and May, stinger suits are worn at some locations because of the risk of box jellyfish, and you will look slightly ridiculous in one.

Allow at least three days in the region, so that one rough or cancelled day does not undo the trip. Choose your base by the experience you want: Cairns and Port Douglas for outer-reef day trips and liveaboards, Airlie Beach for the Whitsundays, and Heron Island or Lady Elliot Island for a night on a cay.

Book an operator with a clear environmental policy and a permit from the Great Barrier Reef Marine Park Authority, the body that manages the park. Smaller groups often mean quieter reefs. Check the weather before booking, because strong winds can make the crossing unpleasant.

More than 70 Traditional Owner groups have connections to the reef, each with their own language, stories and responsibilities for sea country. Their relationship with the sea is one of care and obligation as well as use, and it is recorded in song, art and law.

Many Indigenous-owned businesses now run cultural tours, including walks, guided boat trips and art centres on the coast, and they give visitors a way to learn directly from the people whose country this is. In Cairns, the cultural centres and galleries are a good place to start. Ask your operator about Indigenous partnerships, and be clear that visiting a place is not the same as understanding it, and let them lead.