Earth's Journal

Biosphere Journal Entry

Great Barrier Reef Threatened (October 25, 2010)

Great Barrier Reef

Satellite view of the Great Barrier Reef off the coast of Australia. The reef is suffering from coral bleaching and other threats. NASA.

Australia's Great Barrier Reef, the world's largest living structure, is in trouble. The huge coral reef is threatened by climate change, runoff from farms and cities, and over-fishing. The United Nations Intergovernmental Panel on Climate Change say the reef could become nearly lifeless within a few decades unless stronger action is taken to save it.

Climate change is linked to an increase in coral bleaching on the reef as temperatures rise. The outer layer of a coral reef is made up of living polyps. These are tiny animals that lie on top of the remains of many earlier generations of coral. Warmer water temperatures cause coral to expel the algae they depend on for much of their food. The coral loses its color and turns white. Often, the coral dies. Coral bleaching is a growing threat to reefs worldwide. A recent NOAA study shows reefs in the Caribbean, Southeast Asia, and the western Pacific Ocean are also at high risk.

The Great Barrier Reef is considered one of the wonders of the natural world. The reef stretches for more than 1,200 miles (2,000 km) along the coast of Queensland. It's the largest structure built by living organisms on Earth. The reef is the site of incredible biodiversity. About 1,500 species of fish and hundreds of different invertebrates and plants live on the reef.

Coral reefs are called "rain forests of the sea" because of their rich biodiversity. They support about one-third of all the world's fish species and close to a million different kinds of animals overall.