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Geo-Joint: The Great Barrier Reef

Posted on September 25 2014

Great Barrier Reef

Image Credit: Wikimedia

Go to the northeastern coast of Australia and look east – you can’t miss it.  Except it’s underwater, mostly.  At 2300 kilometers (or about 1420 miles) in length, the Great Barrier Reef more than dwarfs the next two biggest reefs, the Belize Reef at 290 km and Australia’s Ningaloo Reef at 280 km.  And it’s not just a long string – it has enough width to be about half the size of Texas in area.  The Great Barrier Reef isn’t one continuous mass, however.  It comprises 3,000 coral reefs, 600 continental islands, 300 coral keys and roughly 150 inshore mangrove islands.  It’s gotten the “world’s biggest organism” designation from some “world’s biggest” compilers because although it is made up of billions (trillions?) of coral polyps, the reef itself is a shared housing arrangement.  Each individual secretes calcium carbonate and adds to the massive complex.  As individuals die off, their former “house” remains, and gets built on top of, for thousands of years.

And that system worked pretty well up until the 20th century got rolling.  Studies done in the 1920s and ’30s documented a baseline for what the Great Barrier Reef could be, an ecosystem of wonderous richness and diversity.  Forty years later the scientists who had done that early work returned and were appalled at what had happened.  Silt from farming operations had washed down rivers and buried huge areas of coral, smothering them.  Not long after, in 1985, study sites were set up to monitor the health of the reef in over 100 locations.  It has revealed a depressing situation – since the mid-’80s, coral cover has diminished by about 50 percent.  As in half.  In less than ten years, at that rate, another half will be gone.  UNESCO, which once deemed the Great Barrier Reef a World Heritage Site, is considering adding it to their “World Heritage in Danger” list, reflecting a dire outlook.

How can this be happening?  It’s not just the siltation anymore; it’s so many things.  The biggest threat to the reefs are the seasonal cyclones whose heavy seas break off parts of the reef structure, and bring heavy rains which wash huge sediment loads into the sea.  As much as 40% of the reefs’ decline may be attributable to storm damage, combined with the crown-of-thorns starfish.   The crown-of-thorns is a natural inhabitant of the reef – its food source is the coral itself – and under normal circumstances it can live there in a balanced state.  But when excessive nutrient loads are washed into the reef at the same time starfish larvae are developing, inordinate numbers of them survive to overpopulate, and overeat, the reef.

Another 10% of reef damage is laid to coral bleaching, a situation in which organisms that live symbiotically with coral die off due to increased ocean temperature, pollution, disease and other causes.  The other 50% of damage comes from a variety of sources, including the pollution of fertilizer and pesticides coming from farms, the dumping of harbor dredging operations at sea, and the construction of new port facilities.  The double-whammy of the new ports is that they are being built to handle more export of natural gas and coal, the very burning of which brings greater climate change, increasing the size and frequency of the cyclones that hit the reef.

Lastly (maybe) is the staggering threat of ocean acidification caused by the CO2 load in the atmosphere.  Greater ocean acidity actually dissolves the calcium carbonate that the reefs are made of.  How much more abuse can the Great Barrier Reef take?  What can be done to save it?

Efforts are being made to manually kill off the excess crown-of-thorns starfish (an enormous task – just as the starfish  are enjoying a new population boom that could last 10 years), and there are demands to create more laws regarding farm runoff and dredge dumping, but the drivers of climate change are produced worldwide, beyond Australia’s control.  Hard to face is that their own increased carbon energy production feeds the problem just as prospective oil drilling in the Arctic will hasten the melting of the polar ice cap.  Changes of epic proportion will probably be needed to turn the situation around, but sadly, while hands are wringing, the world charges headlong in the wrong direction.

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