The Great Barrier Reef, this Australian natural treasure classified as a world heritage site, is in danger due to ocean warming. Record temperatures have caused “catastrophic” coral bleaching, leading to the disappearance of more than 50% corals observed near an island in the south of the reef last year. This phenomenon not only concerns scientists but also raises questions about our environmental responsibility and the need to act quickly.
Torrid summers that leave their mark
In 2024we witnessed the hottest summer on record at the Great Barrier Reef, with ocean temperatures reaching unprecedented levels. It was the seventh episode of mass bleaching of the reef. Marine heat waves put corals under pressure, forcing them to expel the symbiotic algae that provide them with food and color. Without this algae, corals bleach and often risk death if it lasts too long.
The reasons behind this catastrophe include the continued use of fossil fuels, the main cause of rising global temperatures and global warming. The El Niño phenomenon only made matters worse by pushing ocean temperatures even higher. The message is clear: without a significant reduction in global emissions, we risk seeing these events much more often.
A massacre among the corals
Researchers from the University of Sydney studied 462 coral colonies at One Tree Island over five months. Last May, 370 had already been cleared; two months later, more than half had disappeared. Some species have shown mortality rates of up to 95%. A dramatic phenomenon called “colony collapse”, where the coral skeleton breaks away and disintegrates, has been observed.
The species Goniopora was not spared and contracted black band disease, often fatal for these delicate marine organisms. These massive losses show how vulnerable corals are in the face of rapid climate change.
The Great Barrier stretches almost 345 000 km² and is home to more than 1,500 species fish as well as more 400 types hard corals. It is also a key economic pillar for Australia thanks to the tourism it attracts. But recently, we have observed a worrying trend: marine heat waves are becoming more frequent and intense.
The latest event affected even parts of the reef that had previously escaped mass bleaching. Species once considered resistant are now clearly showing signs of disease and experiencing high mortality.
-What can we do to save our reefs?
From 1998several severe episodes hit the reef in 2002, 2016, 2017, 2020and recently in 2022 during a particularly intense La Niña event. Maria Byrne insists: “Our results show how urgent it is to act to protect coral reefs. » She recalls that these ecosystems are vital not only for biodiversity but also for food security and coastal protection.
The survival of reefs now relies on a collective global effort to limit rising temperatures. Shawna Foo expresses her sadness: “Seeing the damage to a reef that has largely avoided mass bleaching until now is heartbreaking. »
Faced with this alarming situation, everyone is encouraged to think about their role in the fight against climate change. Our collective actions can still reverse this destructive trend and preserve this natural gem for those who come after us.
Source : Limnology and Oceanography Letters
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