Paris (AFP) – Australia's Great Barrier Reef, suffering from severe stress in a warmer, acidic ocean, has been threatened with extinction five times over the past 30,000 years, researchers said Monday.
Reefs could be more resilient than previously thought, it's probably never been as bad as they are today, they added.
"I have great concerns about the ability of the reef in its current form to survive the pace of change, through the many current pressures and projected in the near future," said Jody Webster of the University of Sydney, co-author of one Journal in the journal Nature Geoscience.
In the past, the reef moved along the seabed to deal with changes in its environment – either seaward or landward, depending on whether the sea level was rising or falling, the research team found.
Based on fossil data from cores drilled into the seabed at 16 sites, the Great Barrier Re ef, or GBR for short, was able to migrate between 20 centimeters (7.9 inches) and 1.5 meters per year.
This rate may not be enough to withstand the current flood of environmental problems.
The reef "probably has not faced changes in SST (sea surface temperature) and acidification at such a rate," Webster AFP said. The rates of change "are probably much faster now – and in future projections."
The World Heritage site, which attracts millions of tourists, is suffering from sinking coral bleaching due to climate warming of the sea
Webster and an international team wanted to look at the current plight of the reef in a longer term context.
For more than 10 years, they studied how they had responded to changes in continental ice sheets that stretched over 30 millennia.
– Fish Breeder –
Their research spanned a period prior to the "Last Glacial Maximum" or LGM – the peak frost around 21,000 years ago during the last Ice Age.
The average sea level at that time was about 120 meters lower than today.
When the sea level dropped to the LGM, there were two massive "deaths" – about 30,000 and 22,000 years ago, the team found was caused by the fact that the reef was exposed to the air. What was left of it, climbed seaward, to recover later.
When ice sheets melted after the LGM, two deaths – 17,000 and 13,000 years ago – were attributed to sea-level rise, the team found. In these cases, the reef moved landward.
The fifth death event occurred about 10,000 years ago, apparently due to a massive sediment dump in the midst of higher sea levels.
Webster said that the GBR "will likely be in at least the next few thousand years if it follows its geological pattern," as the Earth is believed to be eligible for another Ice Age.
"But whether human-induced climate change will accelerate remains to be seen."
In April 2016, a study reported that during a violent heatwave in 2016, nearly a third of the reef coral died in a "catastrophic death." has been.
Changes in sea temperature and acidity can "bleach" coral algae that live in their tissues and provide them with food.
Bleached corals are more susceptible to disease, and without enough time to recover, they can disappear forever.
Coral reefs are home to about a quarter of marine life, and serve as a nursery for many species of fish.