we tell you the story of the Great Barrier Reef, in pain due to global warming

There was once a strange, beautiful and flamboyant species that was able to build its own skeleton and multiply. An animal with billions of individuals taking the form of towers, rings or mountains. So solid that it is thought to be mineral. So beautiful that you imagine that plant. One day, future generations might talk about corals as a mythical creature.

As sea temperatures rise and so do atmospheric temperatures, many coral reefs succumb to this new stress. The most famous of those that make up the Great Barrier Reef off Australia are no exception. On the occasion of World Oceans Day, Thursday 8 June, franceinfo dives into the fascinating history of this dying ecosystem.

She lived 20 million years, but rising temperatures shattered her life

Like all coral reefs in the world, the Great Barrier Reef was born out of an unlikely love affair. This romance begins 20 million years ago, in the desolate waters bordering northeastern Australia, desperately poor in nutrients. The coral – a strange cousin of anemones and jellyfish – could have waited peacefully for evolution to settle its bill. But our hero has resources. “To be able to live where there is no food, it has developed an exceptional physiological process: symbiosis, living together between two organisms”explains physiologist Denis Allemand, a specialist in corals.

Its soulmate is a single-celled alga, zooxanthellae. Together, these two species – one animal, the other vegetable – form both a daring mixed couple and one of the oldest co-dependent duos on our planet. Without waiting, the zooxanthellae move inside the coral. In his body, under his exoskeleton. Intrusive? No, vital. “Algae perform photosynthesis and therefore produce oxygen and sugar, which will be used by the coral animal”, explains oceanographer Pascale Joannot. In addition to its colors, coral derives its energy from it. Enough to feed the largest animal structure on the planet: 2,500 reefs spread over 2,300 km in length – the distance between Montpellier and Oslo (Norway) – populated by 400 corals. Their fusional love can be observed from space.

Corals affected by bleaching in Great Barrier Reef off Queensland, Australia, March 7, 2022. (GLENN NICHOLLS / AFP)

But in 1998, the couple faltered. The Great Barrier experiences a first episode of massive bleaching. Under the influence of stress associated with the rise in water temperatures, the coral emits zooxanthellae. This phenomenon constitutes “a divorce”, describes Pascale Joannot and Denis Allemand. The coral loses its color and reveals its white skeleton and especially its reason for living. If the separation lasts too long, the animal dies. A new crisis arises in 2002. Then in 2016 and 2017. And again in 2020 and 2022.

According to Australian researchers, only 2% of the corals in the Great Barrier Reef have escaped a bleaching episode, and more than half of the corals have died since 1995. Under the influence of global warming, “IMass bleaching events occur throughout the Great Barrier Reef. They are becoming more important, but also longer and more frequent “warns Denis German.

It provides tremendous services to nature and our lives also depend on it.

The Great Barrier is not just an unusual animal structure whose towers can rise up to 500 m from the seabed. It is a rich ecosystem in the midst of nothingness. “Corals are often compared to oases in the desert of the sea”explains Denis Allemand. It’s the manta rockers’ Dubai, Nemos Las Vegas. A largely submerged megalopolis, it is home to 1,500 species of fish, 4,000 species of molluscs and 240 species of birds. Thirty species of whales and dolphins frequent it. Six of the seven species of sea turtles recorded in the world live there.

“The wealth created by engineered corals attracts a host of organisms to the reef: 30% of known marine species live in coral reefs.”

Denis Allemand, coral specialist

at france info

Gold, “When the oasis disappears, only the desert remains. It is difficult to survive in the desert”, the coral specialist continues, pointing to the cascading effects of this loss of biodiversity on the food chain. Coral reefs as a whole make up 9-12% of the fish caught worldwide. “People living nearby get 90% of their protein intake from coral reefs”, adds Pascale Joannot. Reefs also nourish souls. They present “a cultural value for these residents: they are found in stories, legends, totems, etc. They have a cultural and religious role”, she insists. Along the Great Barrier Reef, local indigenous communities are working to preserve it. Their jobs as rangers or guides depend on these mythical reefs, a paradise for divers – on land, tourism supports more than 60,000 people.

Fish around the Great Barrier Reef, Australia, 12 February 2019. (ANTOINE BOUREAU / PHOTONONSTOP / AFP)

The Great Barrier feeds them, employs them and “protects the earth from the attack of the sea. A wave that breaks on a dead reef is stopped worse than when it breaks on a healthy reef”continues the biologist. Corals also wish us good luck. Monaco’s scientific center is thus studying corals in their capacity as “magnificent biological model” : “We are working on its ability to regenerate. It also has absolutely phenomenal antioxidant properties (…) or anti-aging properties”, details Denis Allemand. Against certain cancers, against pain, Alzheimer’s disease or osteoarthritis … Each species potentially carries a molecule that will lead to a treatment. A perspective that makes you want to take care of it.

She is dying and our efforts to save her are like a sword in the water.

A reef can recover after a bleaching event in a few years. But the repeated attacks of the disease will one day overcome its resilience and condemn the great barrier. For the reefs that recover have fewer species, and the latter are generally among the least resistant, Pascale Joannot explains.

In an effort to remedy this critical condition, the newly elected Australian government has prescribed a cure for the seriously ill to the dollar: it has promised to inject $ 1.2 billion into the protection of this ecosystem by 2030. as a result of human activity (industrial or agricultural), wage war on plastics, work to restore dying reefs … “We are currently experimenting”, relief pascal Joannot, Carrier of the SOS Corail Participation Program. “There are attempts at transplantation: we take healthy corals from a place where they are doing well, and we try to get them to take them elsewhere. Also nurseries.”quotes the scientist and welcomes the many initiatives taken around the world to protect reefs. “But that will not be enough.”

An Atoll Forming the Great Barrier Reef, Australia, September 21, 2021. (DEICHMANN-ANA / ONLY WORLD / AFP)

To guarantee that a reef will not be affected by a bleaching phenomenon, there is only one antidote:

We can give fine speeches and spend billions, but to save corals, we must slow down global warming caused by human activity.

Pascale Joannot, oceanologist

at france info

For underwater, as everywhere else, the change in temperature – and the accompanying increase in acidityis too fast to allow this ecosystem to adapt, no matter how fascinating and resilient it may be. Thus, the scientific models validated by the IPCC predict that 99% of corals will disappear in the event of a global temperature rise of 2 ° C in 2100.

But according to the comparison of the Climate Analytics programs, it is precisely there that the proposals of the new Australian Prime Minister lead us. Yet presented as determined to tackle the issue of the country’s greenhouse gas emissions directly, this government would therefore also condemn this jewel in the long run, not without having swallowed up what is equivalent to Samoa’s GDP.a state that also sees its coral reefs die – in its security. Coral reefs, including the Great Barrier Reef “would be the first ecosystem to disappear due to humans”notes Denis Allemand.

To avoid this must coral specialist expects a global coral conservation project, “an interim shift“nevertheless ambitious, consisting of recovering a maximum of coral species, to ensure their survival in the laboratory. The researchers thus hope to be able to select these “which we could use when things were better”, species that would withstand a warmer sea. From a natural miracle to life in an aquarium, the fate of the Great Barrier Reef is not sealed. Provided, of course, that the species that abused him rushes to his bed.

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