The figures revealed Tuesday by the Australian Institute of Marine Sciences bloodcurdling: up to 72% coral mortality on the twelve reefs studied. A real massacre caused by a devastating cocktail. Massive bleaching of reefs, the passage of two cyclones and devastating floods.
In some northern sections, a third of hard corals have perished, marking the “ largest annual decline » since government observations began 39 years ago. This monumental living structure, 2,300 km long, may have reached a point of no return.
A deadly summer for corals
The mechanism of destruction is relentless. Under the effect of high temperatures caused by global warming, corals expel their symbiotic microscopic algae, zooxanthellae. This relationship is essential for the survival of the coral. Zooxanthellae, through photosynthesis, provide the coral with much of the energy it needs. In return, the coral offers them an environment protected from algae.
When the surrounding water is too warm, the zooxanthellae produce substances toxic to the coral, forcing it to expel them. If the heat persists, they turn white and eventually die. This year marks the fifth mass bleaching event in just eight years.
Mike Emslie, senior researcher at the Australian Institute of Marine Science, describes the past austral summer as ” one of the most severe » never recorded, with heat stress levels surpassing all previous records. Will 2024 be worse than 2023, which remains, for the moment, the hottest in history?
Acroporas, sentinels of a predicted disaster
Particularly affected, the Acroporas, also called staghorn corals, embody the tragic paradox of this catastrophe. The latter, known for their rapid growth, are also the first to succumb to bleaching. Their exceptional mortality during this episode serves as a very serious alarm signal.
Richard Leck, head of oceans for WWF-Australia, sees his “ worst fears confirmeds” by these preliminary observations. According to him, “ the Great Barrier Reef can regenerate, but its resilience has its limits “. The most worrying thing in this story? This is because the area studied remains “ relatively restricted “, suggesting similar losses across the entire reef when the full report is published next year.
The urgency of a political response
This ecological disaster points directly to Australian responsibility. The world’s largest exporter of gas and coal, the country only recently set carbon neutrality targets. The country has long been a staunch defender of fossil fuels, benefiting from significant subsidies for these industries. These subsidies have thus created a very strong economic dependence and have slowed down the national energy transition.
In addition, the mining industry represents a significant part of the Australian economy and generates a huge number of jobs. The transition to an economy less dependent on fossil fuels comes up against a certain reluctance among political decision-makers, fheavily influenced by mining lobbying. Naturally, the latter defends his sector tooth and nail and opposes the implementation of stricter environmental regulations.
Environmental defenders are therefore calling for greater commitment: a reduction in emissions of at least 90% compared to 2005 levels by 2035, coupled with a gradual abandonment of fossil fuels.
Even if it is far from us, the disappearance of the Great Barrier would sow real ecological chaos. In addition to the loss of the marine biodiversity they support, these reefs play an essential role in protecting coastlines by cushioning the force of waves. Without this natural barrier, coasts would be more vulnerable to erosion, flooding and damage caused by storms. As a complex ecosystem, its disappearance would lead to chain consequences throughout the marine food chain. This barrier is also one of the lungs of our planet, since it absorbs millions of tons of CO every year.2 ; without her, the effects of global warming would accelerate. A phenomenon that we would gladly do without.
- Up to 72% coral mortality has been recorded on some Great Barrier Reef reefs, due to mass bleaching and climate disasters.
- Corals, particularly Acroporas, are suffering record losses, revealing the limits of resilience of this unique ecosystem.
- Australian responsibility in this disaster is singled out, with calls for urgent action against the excessive use of fossil fuels.
