Great Barrier Reef

The Great Barrier Reef is the world's largest coral reef. It is located in the Coral Sea off the coast of Queensland in north-east Australia. It stretches over 2000 kilometres in length and can be seen from space . It is a large system of about 3000 reefs and 900 islands that are mostly offshore.

The reef first became known to Europeans on 11 June 1770 when the explorer Captain James Cook aground on it. The Great Barrier Reef however had already came into existence in the presence of Aboriginal peoples whose occupation of the Australian continent extends back more than 60,000 years.

The Great Barrier Reef is the world's largest coral reef system, composed of roughly 3,000 individual reefs and 900 islands, that stretch for 2,600 kilometres (1,616 mi).The reef is located in the Coral Sea, off the coast of Queensland in north-east Australia. A large part of the reef is protected by the Great Barrier Reef Marine Park.

The Great Barrier Reef can be seen from outer space and is sometimes referred to as the single largest organism in the world. In reality, it is made up of many millions of tiny organisms, known as coral polyps. The Great Barrier Reef was also selected as a World Heritage Site in 1981. CNN has labelled it one of the seven natural wonders of the world.

Due to its vast biodiversity, warm clear waters and its accessibility from the floating guest facilities called 'live aboards', the reef is a very popular destination for tourists, especially scuba divers. Many cities along the Queensland coast offer boat trips to the reef on a daily basis. Several continental islands have been turned into resorts.

Biodiversity
The Great Barrier Reef is made up of many millions of tiny organisms, as are all coral formations .

Many species of animals live in the reef. Some examples are the nudibranchs, hard corals, titan triggerfishers, cone snails, sea anemone and the anemone fish.

A large part of the reef is protected by the Great Barrier Reef Marine Park. However, the Great Barrier Reef is in a risk zone where

water quality has declined due to sediment and chemical runoff from farming, and to loss of coastal wetlands which are a natural filter.

Global Warming
The most significant threat to the future of the Great Barrier Reef is global warming. Many of the corals of the Great Barrier Reef are currently living at the upper edge of their temperature tolerance. Under the stress of waters that remain too warm for too long, corals expel their photosynthesizing zooxanthellae and turn colourless, and if the water does not cool within about a month the coral dies.

Other Threats
The Great Barrier Reef also experience threats like overfishing, and natural treats such as the Crown-of-thorns sea star(below). Armed with poison spikes and an appetite for hard coral, adult crown-of-thorns sea stars can kill a reef. By projecting their stomachs out of their mouths and wrapping them around coral, they slowly devour it. Divers are sometimes trained to kill sea stars .