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The Great Barrier Reef may survive rising sea levels, but not in the presence of climate stress and pollution, suggests a new study published by the University of Sydney. A look into the geological past offers worrying prospects for the future of the world's largest coral ecosystem, Xinhua reported.
• Reef 4: The ancestor of the Great Barrier Reef and the forgotten lesson of extinction
Researchers from the University of Sydney analyzed an ancient reef, called "Reef 4", considered a proto-Great Barrier Reef, which existed about 11,000 years ago. The study, published in the prestigious journal Nature Communications, revealed that the reef managed to survive a period of rapid sea level rise - but eventually succumbed to a combination of additional stressors.
These included rising temperatures, declining water quality, and sediment and nutrient loadings, similar to those the modern reef faces today.
• A climatic past that mirrors the present
The study covered the period between 11,450 and 11,110 years ago - an era marked by accelerated melting of polar ice and rapid sea level rises. The researchers took 15- to 20-meter-long fossil coral cores from depths of 40 to 50 meters below the seabed to reconstruct the evolution of the ancient reef. The results showed that during that time, sea levels rose by 3-5 millimeters per year - a rate comparable to today's rate, but significantly less extreme than previously estimated.
• Survival conditioned by lack of environmental stress
Reef 4 managed to adapt and survive this sea rise. But with the onset of a combination of environmental pressures - rising temperatures, polluted water, and prolonged heat stress - the ecosystem collapsed. Its demise was recorded around 10,000 years ago. The study's coordinator, researcher Jody Webster from the University of Sydney, explained: "Modern corals are facing a similar combination of factors: rising sea levels, increasingly frequent marine heat waves, extensive bleaching episodes, and excessive sediment and nutrient deposition. This overlapping of stressors is deeply concerning.”
• What's next for the Great Barrier Reef?
Webster predicts that the Great Barrier Reef could survive these pressures, but only at the cost of major transformations. "It is likely to become less diverse and structurally simpler in the next 50 to 100 years,” he said.
Such a scenario would have profound consequences not only for marine biodiversity but also for local industries that depend on the reef - tourism, fishing and coastal protection.
• International collaboration for marine science
The study was carried out as part of the International Ocean Discovery Program - a global initiative dedicated to marine research - and brought together specialists from several prestigious universities: the Australian National University, the University of Tokyo and Nagoya University in Japan, the University of Granada in Spain and the University of Aix-en-Marseille in France. This interdisciplinary research combined geology, paleoclimatology, oceanography and coral ecology to reconstruct the most complete picture possible of the past and its implications for the future.
"Understanding the environmental changes that influenced Reef 4 and ultimately led to its demise provides clues about what might happen to the modern reef,” concluded Jody Webster. This insight highlights the urgency of reducing anthropogenic pressures on marine ecosystems. Protecting water quality, reducing greenhouse gas emissions, and conserving biodiversity are essential steps if the Great Barrier Reef is not to become another fossil of the future. The Great Barrier Reef has survived crises before. But the lessons of its geological ancestors make it clear: nature can endure, but not forever.
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