It’s enormous… the Great Barrier Reef is the largest reef system in the world. It is made up of over 3000 individual reefs stretching over 1800 miles from Papua New Guinea down the Queensland coast off north-eastern Australia. It is in fact so large that it is the only living thing visible from space, covering approximately 348000 square kilometres: the area of Belgium, Ireland and the United Kingdom combined. The reef attracts over 3000 species of molluscs, 1600 species of fish and 400 species of the dazzling coral for which the area is known, in addition to the numerous species of birds, mammals and plants which call it home. Islands in the reef are also key nesting sites for loggerhead and green sea turtles, which are both endangered species. It is therefore obvious to see why this has been named one of the seven wonders of the natural world and deemed a World Heritage area since 1981. However, this colossus is under great strain from multiple risks, such as coral bleaching caused by phenomena including climate change and extreme weather patterns, as well as agriculture, trade and tourism.
Historically, the Reef has been inhabited and fished by native Aboriginals for over 40000 years, but it is only within the last 500 that Western explorers have gazed upon the natural beauty. Captain Cook grounded HMS Endeavour on the reef in 1770 and HMS Pandora was wrecked there in 1791, propelling knowledge of the existence of the reef into the international community. Ever since, ships have been falling foul of the shallow waters of the reef. Only last year, in April 2010, a Chinese coal ship ran aground, after straying from the shipping channels, leaving a kilometre long scar on the reef. Toxic paint scraped off the ship killed coral and the hull was breached, spilling two tonnes of oil into the Coral Sea. This has led to the Australian Government introducing tighter restrictions and harsher penalties with regard to commercial shipping in the region.
However, the Great Barrier Reef is under a much larger threat than damage from the odd shipwreck. Rising sea temperatures are catastrophic for coral, killing them if the temperature does not fall back within the safe range. Coral is an organism made up of many microscopic polyps, secreting a white calcium carbonate shell, which the multicoloured zooxanthellae algae can colonise. The algae produce nutrients from sunlight, via photosynthesis, hence reefs are found in shallow water. However, the algae only inhabit the coral in a small temperature range. When the sea temperature rises, the coloured algae die or vacate the coral, leaving the white shell, leading to the term coral bleaching. Scientists studying the reef believe this will become an annual phenomenon, when the sea temperatures rise in the summer.
Agricultural pesticide run-off into the Coral Sea around Queensland is also toxic to coral. This year’s Cyclone Yasi that hit Queensland increased the leaching of pesticides into flood water, which flowed into the Great Barrier Reef. As well as lethal pesticides threatening the coral, sediment flowed into the reef, blocking sunlight and reducing photosynthesis. The huge volume of fresh water pouring into the reef was also harmful to the coral. Some individual reefs were pulverised by the force of the storm, and scientists estimate the reef will take over 20 years to recover.
With the threat of annual coral bleaching, shipping accidents, increasing usage of toxic pesticide and freak weather patterns, the Great Barrier Reef faces an uncertain future. One fact is undeniable, with two million tourists visiting the area every year and an estimated four billion dollars bolstering the economy per annum, this is one attraction Australia cannot afford to lose.
Image credit – babasteve