Great Barrier Reef lost half of coral

No time to lose-greenhouse gas emissions need to be reduced as soon as possible

Study author

“Loss of large corals is important because they make all babies. They are responsible for most of the annual breeding carried out by adult corals,” said Professor Hughes.

Studies have documented the rapid deterioration of coral colonies in the northern and central parts of the Great Barrier Reef after the climate crisis caused ocean heat waves and bleached large numbers of corals in 2016 and 2017.

Coral dead on the Great Barrier Reef. credit:Tony Chase

The southern part of the reef was also exposed to record temperatures and extensive bleaching in early 2020 (this data was not included in the study).

Coral relies on algae known as zooxanthellae to provide most of the energy and much of the bright colors. When exposed to persistent abnormal heat (measured on so-called hot days), corals begin to expel algae, leading to massive bleaching.

Branched table-shaped corals provide shelter and habitat for fish and other coral reef inhabitants, and their loss reduces fish numbers and reef fishery productivity.

Bleached on the Great Barrier Reef coral reef near Cooktown in March 2020.

Bleached on the Great Barrier Reef coral reef near Cooktown in March 2020.credit:Via Terry Hughes

“These types of corals are three-dimensional and create the corners and crevices that are essential to the biodiversity of coral reefs,” says Professor Hughes.

Researchers have found that better data on coral vital trends are needed to understand how coral populations are changing.

“I thought the Great Barrier Reef was protected by its size, but the results show that even the world’s largest and relatively protected coral reef system is becoming more and more endangered and declining. “Yes,” said Professor Hughes.


The author is concerned about narrowing the gap between bleaching phenomena, as corals have little chance of bouncing back.

“We have no time to lose. We need to reduce greenhouse gas emissions as soon as possible,” the research paper says.

According to Professor Hughes, global temperature rises need to stabilize between 1.5 and 2 degrees Celsius to maintain coral reefs, even if they are quite different from current temperatures. “Forget if it’s 3 or 4 times.”

In February of this year, the Bureau of Meteorology recorded the highest monthly sea surface temperature ever recorded on the Great Barrier Reef since it began in 1900.

The warming seas are affecting some coral reefs in Melanesia and Indonesia around the world, including off Brazil.

Miki Perkins is a senior journalist and environmental reporter at The Age.

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Great Barrier Reef lost half of coral

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