Sep 20, 2011
7 Wonders of the Natural World - Part II
The Great Barrier Reef is the largest coral reef in the world. It’s made up of over 2,900 separate reefs, stretching over 1,600 miles (2,600 km). The reef is located in the Coral Sea, off the coast of Queensland in north-east Australia. Larger than the Great Wall of China, it is the world’s largest single structure made by living organisms and is visible from space.
The Reef is a site of remarkable beauty and variety, containing the world’s largest collection of coral reefs, with 400 types of coral. It also holds great scientific interest as the habitat of species such as the dugong (‘sea cow’) and six of the world’s seven species of sea turtle.
The variety of life along the Reef's vast expanse is immense. The Reef's unique biodiversity of species and habitats make the Great Barrier Reef and surrounding areas one of the most complex natural systems on Earth. Its great diversity reflects the maturity of an ecosystem which has evolved over millions of years on the north-east continental shelf of Australia. The site contains a huge mixture of species including over 1,500 species of fish, about 360 species of hard coral, 5,000 species of mollusc, and more than 175 species of bird, plus a great diversity of sponges, anemones, marine worms and crustaceans, among others.
The reef system, extending to Papua New Guinea, comprises some 2900 individual reefs of all sizes and shapes covering more than 12,500 square miles (20,000 square km) including 760 fringing reefs, which range in size from under 1 hectare to over 10,000 hectare and vary in shape to provide the most spectacular marine scenery on Earth. There are approximately 600 continental islands including many with forests and freshwater streams, and some 300 coral cays and sand cays.
Two main classes of reef structure may be defined: platform or patch reefs, resulting from radial growth; and wall reefs, resulting from elongated growth, often in areas of strong water currents. There are also many fringing reefs where the reef growth is established on sub-tidal rock of the mainland coast or continental islands.
The site includes major feeding grounds for the endangered dugong and nesting grounds of world significance for two endangered species of marine turtle, the green and the loggerhead, as well as habitat for four other species of marine turtle. Given the severe pressures being placed on these species elsewhere, the Great Barrier Reef may be their last secure stronghold. It is also an important breeding area for humpback and other whale species.
A wide range of fleshy algae occurs, many of which are small and inconspicuous but which are highly productive and are heavily grazed by turtles, fish, molluscs and sea urchins. In addition, algae are an important component of reef building processes. 15 species of sea grass grow throughout the reef area forming over 1,800 square miles (3,000 square km) of sea grass meadows and providing an important food source for grazing animals, such as dugongs.
Because of its natural beauty, both below and above the water's surface, the Great Barrier Reef has become one of the worlds most sought after tourist destinations. The weather is tropical, and is fairly consistent being neither extremely hot nor extremely cold. The summer temperatures range from 73 to 91 degrees and the winter months range from the upper 50s to the mid 70s. The rainy season occurs from November through May which accounts for over 75% of the annual rainfall during this period.