The Great Barrier Reef is the barrier of coral largest in the world, composed of over 2,900 individual reefs and 900 islands stretching 2,600 km , over an area of approximately 344,400 km˛. It is located off the coast of Queensland , in ' Australia north-east. The Great Barrier Reef can be seen from outer space and is the largest structure made of a single living organism. The structure is composed of billions of tiny organisms, known as coral polyps . The barrier has a great biodiversity , and has been included as a World Heritage Site in 1981 . The CNN has included in its seven wonders of the world. A large part of the reef is protected by the Great Barrier Reef Marine Park , which helps to limit the human impact, such as overfishing and tourism . Other environmental pressures to the reef and its ecosystem are the water quality of runoff , climate change, along with coral bleaching.