Global alert: Great Barrier Reef faces historic disaster

© Egor Kamelev/Pexels

The figures revealed Tuesday by the Australian Institute of Marine Sciences cast a chill over the blood: up to 72% coral mortality on the twelve reefs studied. A real massacre caused by a devastating cocktail. A massive bleaching of the reefs, the passage of two cyclones and devastating floods.

In some northern sections, a third of the hard corals have died, marking the ”  largest annual decline ” since government observations began 39 years ago. This monumental living structure, 2 km long, may have reached a point of no return.

Satellite view of the east coast of Queensland, Australia, highlighting the Great Barrier Reef (dark area to the right of the coast) ), the largest coral ecosystem in the world. © Screenshot/Google Maps

A deadly summer for corals

The destruction mechanism is relentless. Under the effect of high temperatures caused by global warming, corals expel their symbiotic microscopic algae, zooxanthellae. This relationship is essential to the survival of the coral. Zooxanthellae, through photosynthesis, provide the coral with much of the energy it needs. In return, the coral provides a protected environment for the algae.

When the surrounding water is too warm, the zooxanthellae produce substances toxic to the coral, which forces it to expel them. If the heat persists, they bleach and eventually die. This year marks the fifth mass bleaching event in just eight years.

Mike Emslie, a senior researcher at the Australian Institute of Marine Science, calls this past austral summer “one of the most severe” on record, with heat stress levels surpassing all previous records. Will 2024 be worse than 2023, which remains, for the moment, the hottest year in history??

Acroporas, sentinels of a disaster foretold

Particularly affected, 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 about this story ? is that the area studied remains ” relatively small “, suggesting similar losses across the reef when the full report is released next year.

The urgency of a policy response

This ecological disaster points directly to Australia's responsibility. The world's largest exporter of gas and coal, the country has 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 created a very high economic dependency 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 amount of employment. The transition to an economy less dependent on fossil fuels is encountering a certain reluctance from political decision-makers, strongly influenced by mining lobbying. Naturally, the latter is fiercely defending its sector and is opposed to the implementation of stricter environmental regulations.

Environmental defenders are therefore calling for a more pronounced 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 away, the disappearance of the Great Barrier Reef would sow real ecological chaos. In addition to the loss of marine biodiversity that it shelters, these reefs play a vital role in protecting coasts by cushioning the force of waves. Without this natural barrier, coasts would be more vulnerable to erosion, flooding and storm damage. As a complex ecosystem, its disappearance would have knock-on effects on the entire marine food chain. This barrier is also one of the lungs of our planet, since it absorbs millions of tonnes of CO2 each year; without it, the effects of global warming would accelerate. A phenomenon that we would gladly do without.

• Up to 72% coral mortality has been observed on some reefs of the Great Barrier Reef, due to mass bleaching and climate disasters.
• Corals, particularly Acroporas, are suffering record losses, revealing the limits of resilience of this unique ecosystem.
• Australia's responsibility for this disaster is being pointed out, with calls for urgent action against the excessive use of fossil fuels.

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