A large reef has lost half of its coral


(CNN) – Australia’s Great Barrier Reef has lost 50% of its coral population over the past three decades, when climate change was a key factor in coral reef destruction, a new study has been found.

Researchers from the ARC Center of Excellence for Coral Reef Studies in Queensland, northeastern Australia, assessed the coral community and the size of their colonies along the Great Coral Reef between 1995 and 2017. depletion of almost all coral populations. They said it on Tuesday.

Coral reefs are one 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 an area of ​​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 found that the number of small, medium and large corals on the Great Barrier Reef has decreased by more than 50% since the 1990s,” said co-author Terry Hughes, a senior professor at the ARC Center of Excellence for Coral Reef. Studies.

Coral reefs are essential for the health of marine ecosystems: without them, ecosystems will collapse and marine life will die.

The Great Barrier Reef covers nearly 133,000 square miles.

Francois Gohier / VWPics / Universal Images Group / Getty Images

Coral populations are also considered necessary for their ability to reproduce corals.

“The living coral population has millions of tiny little corals and many large mothers that produce most of the larvae,” Andy Dietzel, a doctoral student at the ARC Center of Excellence for Coral Reef Studies, said in a statement. .

“Our results show that the resilience of the Great Barrier Reef – its resilience – is at stake compared to the past because there are fewer children and fewer large adults,” he added.

Experts found that population declined in both shallow and deep-sea coral species, but branched and table corals, which provide habitat for fish, were most affected by mass bleaching in 2016. and in 2017, which caused record temperatures.

Taken on 22 September 2014, this image shows fish swimming on the corals of Australia's Great Barrier Reef.

The report’s authors warn that climate change is leading to an increase in the frequency of “cliff disruption”.

William West / AFP / Getty Images

Warm ocean temperatures are a major factor in coral bleaching when corals turn white as a response to stress from water that is too hot. Coral bleaching does not kill immediately, but if temperatures remain high, the coral will eventually die and destroy the natural environment of many marine life species.

Tuesday’s study found a sharper deterioration of coral colonies in the northern and central Great Barrier Reef after the 2016 and 2017 mass bleaching events.

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.

The report’s authors warned that climate change is leading to an increase in the frequency of “coral reef disruptions” such as sea heat.

“There is no time to waste: we must drastically reduce greenhouse gas emissions as soon as possible,” the report’s authors warned in a paper published in the Proceedings of the Royal Society.

Helen Regan of CNN contributed to this report.

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