Unlike the Great Wall of China, which is ridiculously small in comparison, it can be seen from space. The Great Barrier Reef, the only one of its kind in the world, has more than 2,900 reefs and some 900 islands stretching more than 2,600 kilometres from Bundaberg to the tip of Cape York off the coast of Australia. With an area of more than 344,400 square kilometres, it is without doubt one of nature’s greatest masterpieces, a biodiversity wonder which is home to more than 3,000 varieties of molluscs, home to 1,625 different species of fish, hundreds of varieties of jellyfish, sharks and rays, which depend on it for their survival.
Yet this jewel of planet Earth, which began to form more than 18 million years ago, is, in the opinion of many scientists, on the verge of destruction. In a critical state, the “largest living organism in the world” would have the equivalent of a “terminal cancer”…
Worse: the situation would have reached an “irreversible” point… in large portions of the reef, where the corals now have no hope of even healing.
The famous “cancer” that gangrenates the Great Barrier Reef is coral bleaching, or coral bleaching. This is a phenomenon of massive coral dieback, which results in a discoloration of the reef. It is caused by the disappearance of zooxanthellae, microscopic algae that live in symbiosis with the corals: in exchange for shelter and sufficient light exposure, they provide their host with oxygen and nutrients, on which tropical coral depends essentially for its survival.
But here it is: when the coral is under stress, it reacts by expelling these micro-organisms. They can also die due to the loss of pigmentation in these algae. As a result, the corals eventually die of starvation or disease…
In the affected areas, only their skeletons remain, white, lifeless structures that stretch for miles around. These vast areas are called “dead zones.” as coral is an “umbrella species”, i.e. a key organism in its ecosystem, all other animals, fish and shellfish die in turn, or are forced to leave. These places now form a gigantic underwater desert, a sad graveyard devoid of life.
Historically, there have only been four periods of massive coral bleaching: in 1998, 2002, 2016 and now in 2017. These events are triggered by a stress reaction of corals that forces them to eject the microorganisms algae necessary for their survival: this may be due to a change in water temperature (global warming) but also to an increase in acidity, due to excess CO2 produced in the atmosphere by human activities, or polluting products discharged into the ocean, or even all three at the same time.
Corals affected in this way do not necessarily die, and it may take only a few decades to achieve partial recovery, because even though it is fragile, the great richness of biodiversity gives it a strong power to regenerate. But when organisms die in very large numbers, the situation can reach a critical point that can make it irreversible, representing a form of clinical death of the coral structure.
Thus, a total of 20% of the world’s reefs have already been permanently and irretrievably destroyed in recent years. And it is estimated that 50% of the world’s corals will be threatened within the next thirty to fifty years (corals in colder seas are less affected).
Scientists resigned: “We have given up hope”
As far as the Great Barrier Reef is concerned, the results are terrifying, according to the latest studies that have been carried out to assess its state of health. Australian researchers from James Cook University published the results of their latest observations in an official statement… And to say the least, it is not very reassuring.
Two thirds of the Great Barrier Reef would be directly threatened: Of the 2,600 kilometres that make up the organic superstructure, more than 1,500 kilometres would now be bleached. Irrecoverable damage, the scientists say, because the corals have already suffered severe trauma in 2016 and have not had time to recover.
Interviewed by the British title The Guardian, the researchers do not hide their pessimism, despondency and disgust: “We’ve given up all hope”, said Jon Brodie, a water quality expert, castigating in passing the failure of the Australian Government’s actions and the lack of response from the international community in recent years. “I have sacrificed my entire life trying to improve water quality. We have failed. » A resignation all the more unbearable to hear, a fatalism all the more intolerable because it is that of people who have carried body and soul the fight for the preservation of corals, who have devoted their lives to the study of these organisms.
Unfortunately, and even if it is as painful to write about, we will probably be the last generation to have the chance to admire the grandiose beauty of what remains of the Great Barrier Reef. With global warming leading to an increasing rise in global temperatures, coral bleaching is inevitably not going to be stopped any time soon.