[Australia] The world’s largest coral reef system, visible even from outer space, has lost half of its coral in the past two years. The Great Barrier Reef, once a colorful and visible display of biodiversity and a symbiotic ecosystem, now resembles a ghost town where life once flourished.
The Great Barrier Reef, which stretches for 1,400 miles along Australia’s coast, suffered an unprecedented coral bleaching event in the summer of 2016, followed by another bleaching event in 2017. The impact of these two back to back bleaching events is just now coming into focus, with coral reef ecologists documenting a 50 percent decline in corals across the reef in the past 2 years.
Corals and their symbiotic relationship with photosynthetic algae are a delicate relationship. Corals do not make their own food, just like humans, and thus require the intake of food to sustain themselves. However, unlike humans who eat and digest plants and animals for energy, corals provide a safe home for zooxanthellae to live within their polyps. In exchange for a safe place for the zooxanthellae (algae) to live, the algae photosynthesize energy and provide such energy to the corals. The algae also produce oxygen and help the coral filter out waste, a truly unique symbiotic relationship.
However, when the average temperature of the ocean water in which a coral lives is raised by just a degree or two, the coral become stressed and eject their algae tenants. This triggers a slow and steady starving of the coral if they do not accept zooxanthellae back into their polyps in time. The ejection of algae by coral is the process in which we call coral bleaching, as it removes the colorful algae from corals, leaving their stark carbonate structure colorless. Once this happens, a clock begins to tick on the remaining time the coral has to live if it doesn’t resume its symbiotic relationship with algae.
The summer of 2016 marked a double punch to the Great Barrier Reef, a combination of both a continued warming of the equatorial oceans from climate change and the presence of the strongest El Niño event ever recorded. The El Niño Southern Oscillation is a cycle of natural climatic changes that impact the equatorial Pacific. It is the cycle of warm and cold temperatures in the ocean surface along the equatorial Pacific, driven by high air pressure in the western Pacific Ocean and low air pressure in the eastern Pacific Ocean.
The combination of both human-induced climate change and El Niño resulted in a warming of the waters surrounding the Great Barrier Reef and the death of one-third of the corals in the reef system. The result of the 2016 and subsequent 2017 bleaching events was published recently in the journal Nature. The study found that one-third of corals in the Great Barrier Reef died in just a nine-month span in the summer and fall of 2016.
The Great Barrier Reef was always considered the most stable and protected reef system in the world. This is due to the Australian government’s strict protection of the reef, its remote location, and equatorial location. However, the recently published study finds that even the strongest and healthiest coral reef system in the world is no match for the methodological rise in ocean temperatures.
John Bruno, a marine biologist from the University of North Carolina at Chapel Hill shared with The Atlantic results from a yet to be published academic paper. He noted that in the summer of 2015 there were 2 billion corals living in the Great Barrier Reef and since then half of them are now dead.
The Great Barrier Reef is at a tipping point, where it will likely not be the same for centuries. Many of the coral in the reef were decades old, meaning the corals would need decades of healthy uninterrupted living to hopefully rebuild the established coral system. However, a continued warming of the planet and burning of fossil fuels makes that ever more unlikely.
While on a global scale, governments have agreed to limits on warming set forth by the Paris Agreement, the United States has recently announced it would leave the agreement. The Paris Agreement aims to limit the world’s average temperature rise compared to pre-industrial levels by 2 degrees Celsius. However, time will tell how that plays out and whether the world’s governments can slow and stop man-made climate change.
Photo: Aerial view of heart-shaped Heart Reef, part of the Great Barrier Reef of the Whitsundays in the Coral sea, Queensland, Australia. (Photo by: Arterra/UIG via Getty Images)
View original article at: Half of the great barrier reef has died since 2016
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