Great Barrier may lose its World Heritage status due to its degradation
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“They present corners and crevices where many fish and creatures take refuge, and losing those huge three-dimensional corals will change the entire ecosystem”, he considers.
In addition to its priceless value from a natural or scientific point of view, it is estimated that the coral reef, which extends over 2300 kilometers in length, generates four billion dollars in revenue for the Australian tourist sector.
The Great Barrier may lose its World Heritage status due to its degradation, which is due in large part to the recurrence of coral bleaching episodes, which is a consequence of climate change.
Bleaching is a wear phenomenon that results in discoloration. It is caused by increased water temperature, which causes the expulsion of symbiotic algae that give coral its color and nutrients.
Reefs can recover if the water cools, but they can also die if the phenomenon persists.
Australia’s Great Barrier Reef is also threatened by agricultural runoff, economic development and a species of starfish that feeds on corals.
The northern part of this ecosystem had already suffered, in 2016 and 2017, two unprecedented episodes of bleaching of its corals and, last year, Australia reformulated the future perspectives for this group, now considered “very bad”.
Before, two other episodes of coral bleaching were recorded, in 1998 and 2002. A fifth episode was observed this year, but the damage has not yet been fully assessed.
“The vitality of a coral population is characterized by the presence of millions of corals of all sizes, including the largest, which produce most of the larvae,” said study co-author Andy Dietzel, also from James Cook University.
Hughes estimates that corals will continue to die unless countries around the world live up to the commitments made in the 2015 Paris Agreement to contain rising global temperatures below two degrees, compared to their pre-industrial levels.
“The fastest growing species take a decade to recover by half,” said Hughes. “Now, the chances of decades between the sixth, seventh and eighth episodes of bleaching are almost zero, as temperatures continue to rise,” he added.
If temperatures stabilize over the century below the targets set by the Paris Agreement, the reefs may partially recover.
“We don’t think they will recover in the diversity that we know historically”, says the expert, stressing that, if the increase is of three or four degrees, it will be better to “forget”.
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