Great Barrier Reef

Great Barrier Reef, chain of coral reefs in the Coral Sea, off the north-eastern coast of Australia. The largest deposit of coral in the world, the reef extends about 2,010 km (1,250 mi) from a point near Mackay, Queensland, to the Torres Strait, which lies between Australia and New Guinea.

The channel that separates the reef from the Australian coast varies in width. Certain northern parts of the reef are as close as 16 km (10 mi) to the coast. In the south, the channel reaches a width of about 240 km (150 mi). The reef protects the channel from the harsh wind and waves of the Coral Sea. Water in the channel is calm and shallow. Islets and rings of coral called atolls are scattered throughout the channel, making ship navigation difficult.

The Great Barrier Reef is home to a remarkable number of organisms. The coral itself is made up of the skeletons of tiny, flower-like water animals called polyps (a kind of hydra), held together by a limestone substance produced by a type of algae. Hundreds of species of polyps form coral in a beautiful range of colours and shapes. The reef also supports many larger water animals, including more than 1,000 species of fish.

Since the early 1960s crown-of-thorns starfish have invaded parts of the reef. These animals feed on coral and can destroy large portions of a coral reef. The Australian government has made efforts to limit destruction of the coral and in 2004 a law was passed that prohibited fishing in around one third of the reef’s area. Australia’s leading tourist destination attracts around 1 million visitors each year. It was designated a UNESCO World Heritage Site in 1981.