With the austral summer just ended, the Great Barrier Reef experienced its worst episode of coral bleaching, Australian researchers announced on Tuesday, believing that global warming was threatening the very survival of this Australian gem listed as World Heritage.
After a major study last month, Professor Terry Hughes of James Cook University (Australia) announced that the Great Barrier Reef, which stretches 2,300 km, had experienced a new episode of bleaching, the third in five years, due to record water temperatures.
"Serious phenomena"
Whitening is a wasting phenomenon which results in discoloration. It is due to the rise in water temperature, which leads to the expulsion of symbiotic algae which give the coral its color and its nutrients. Reefs can recover if the water cools, but they can also die if the phenomenon persists.
"We surveyed 1,036 reefs from the air in the second half of March to measure the extent and severity of coral bleaching across the Great Barrier Reef," said Terry Hughes. “For the first time, serious bleaching phenomena have been observed in the three major regions of the Great Barrier Reef, the north, the center and large portions of the southern sector. "
Soon a site in danger?
The water temperature in the Great Barrier Reef region was the highest in February since the surveys began in 1900. The Great Barrier Reef, listed as a World Heritage Site since 1981, is an important source of income for the Australian tourism sector. The entire 345,000 square kilometers had barely avoided being placed by Unesco on its list of sites in danger in 2015.
The Barrier is also threatened by agricultural runoff, by economic development and by the purple acanthaster, a starfish devouring corals. The north of this ecosystem had already undergone two unprecedented episodes of coral bleaching in 2016 and 2017 and Australia had reviewed the outlook for this complex last year, now considering them as "very bad".
Government accused of de-dramatizing
Scott Morrison's Conservative government is accused of dragging its feet in the fight against global warming so as not to sacrifice the lucrative coal industry that employs thousands of Australians. The first episode of coral bleaching was observed on the Great Barrier Reef in 1998.
But the continuous rise in temperatures caused by global warming has increased the frequency of the occurrence of this devastating phenomenon. Morgan Pratchett, a professor at James Cook University, said that after the aerial reconnaissance, underwater studies would be conducted to assess the health of the reefs.
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