“There is no way out, no loopholes. The Great Barrier Reef will be over within 20 years or so.”, Charlie Veron, former chief scientist of the Australian Institute of Marine Science, told The Times.
The Great Barrier Reef
The Great Barrier Reef is the world’s largest coral reef system comprising over 2,900 individual reefs and 900 islands stretching more than 3,000 kilometres (1,600 miles) over an area of approximately 344,400 square kilometres (133,000 square miles).
The Great Barrier Reef which is formed by 400 types of coral, is inhabited by 1,500 species of fish and 4,000 types of mollusc. It was recognised as a World Heritage Site in 1981 and CNN has labelled it as one of the seven natural wonders of the world. It is claimed to be the world’s biggest single structure made by living organisms, since the reef structure is composed of and built by billions of tiny coral polyps.
Coral Bleaching and Reef Destruction
Many corals and especially those in shallower waters, depend for up to 90% of their energy requirements on a microscopic algae, Zooxanthellae, that live in the tissue of the coral. The characteristic colour of corals are due to the photosynthetic compounds of the Zooxanthellae.
Rising water temperatures cause the coral to eject the Zooxanthellae with disastrous results as most of these coral are unable to feed themselves. Not only do they loose their colour, becoming transparent and exposing the coral’s bright white skeleton, but they begin to starve. Because of the loss of colour the process is termed bleaching. If the temperature returns to normal, corals can regain their zooxanthellae, return to normal colour and survive. The stress, however, is likely to cause decreased coral growth and reproduction, and increase the susceptibility to disease. Bleached corals often die if the stress persists, reefs then take many years or decades to recover.
This mechanism is well known and has been observed in times of abnormal weather patterns such as the El Niño of 1997-98 when bleaching was widespread. These climate changes are cyclic and although they have caused great damage, the reefs have been able to recover.
Global Warming & Coral
The concern is that with a steady and ongoing temperature rise as predicted by climate change models, the coral will not get a chance to recover and could become extinct.
After a crucial meeting on the future of coral reefs in London early in July, The Zoological Society of London, the Royal Society and the International Programme on the State of the Ocean (IPSO) warned that by mid-century extinctions of coral reefs around the world would be inevitable.
The effect of increases in water temperature are aggravated by the increasing acidity of the world’s oceans. This is driven in the higher latitudes where atmospheric carbon dioxide concentrations are higher and it dissolves more easily because of the increase in solubility at lower temperatures.
What is the Solution
The risk to the future of the coral reefs gives addition impetus to the actions to reduce greenhouse gas emissions and address global warming.
The London meeting renewed calls for networks of marine conservation zones to boost the resilience of reefs.
Image by NASA in Wikimedia Commons and is in the public domain.
