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The Great Barrier Reef has lost 50% of its coral populations over the past three decades, with climate change a key driver of the reef disturbance, a new study has found.
Researchers from the ARC Center of Excellence for Coral Reef Studies in Queensland assessed coral communities and the size of their colonies along the Great Barrier Reef between 1995 and 2017.
They said they found almost all coral populations to be depleted.
Coral reefs are some of the most vibrant marine ecosystems on the planet – between a quarter and a third of all marine species rely on them at some point in their life cycle.
The Great Barrier Reef, the largest coral reef in the world, covers nearly 133,000 square miles and is home to over 1,500 species of fish, 411 species of hard coral, and dozens of other species.
“We have found that the number of small, medium and large corals on the Great Barrier Reef has decreased by more than 50% since the 1990s,” co-author Terry Hughes, distinguished professor at the ARC Center of Excellence for Coral Reef Studies, said. said in a statement.
Coral reefs are critical to the health of marine ecosystems.
Without them, ecosystems collapse and marine life dies.
The size of the coral population is also considered vital when it comes to the reproductive capacity of the coral.
“A vibrant coral population has millions of tiny little corals, as well as many large ones – the big mothers that produce most of the larvae,” said Andy Dietzel, a PhD student at the ARC Center of Excellence for Coral Reef Studies. .
“Our results show that the resilience of the Great Barrier Reef – its resilience – is compromised compared to the past, because there are fewer children and fewer large adults.”
Experts found that the population decline occurred in both shallow and deep-sea coral species.
But branching and table-shaped corals, which provide habitat for fish, were the hardest hit by the mass bleaching events in 2016 and 2017, triggered by record temperatures.
Warm ocean temperatures are the main driver of coral bleaching, when corals turn white as a response to stress from water that is too hot.
Natural habitats destroyed
Bleaching does not immediately kill coral, but if temperatures remain high, the coral will eventually die, destroying a natural habitat for many marine life species.
The study found steeper deteriorations of coral colonies in the northern and central Great Barrier Reef following the mass bleaching events in 2016 and 2017.
The Great Barrier Reef has undergone several mass bleaching events over the past five years, and experts said the southern part of the reef was also exposed to record temperatures in early 2020.
“We thought the Great Barrier Reef was protected by its size, but our results show that the world’s largest and relatively well-protected reef system is also increasingly compromised and in decline,” Hughes said.
‘There is no time to lose’
The report’s authors warned that climate change is driving an increase in the frequency of “coral reef disturbances” such as marine heatwaves.
“There is no time to waste – we need to drastically reduce greenhouse gas emissions as soon as possible,” the report’s authors warned in the paper, published in the journal Proceedings of the Royal Society.
Helen Regan of CNN contributed to this report.
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