Australia’s Great Barrier Reef has lost half its corals due to climate change

DOUGLAS, Australia — While most people focus on how climate change affects life on land, a study finds it’s also having a devastating impact under water. Researchers in Australia say the Great Barrier Reef has lost half of its corals over the last three decades.

The Great Barrier Reef is the largest coral reef system in the world. Sitting off the coast of Australia, it is home to thousands of reefs, shoals, and islets in the Pacific Ocean, spanning over 1,200 miles.

Although many studies look at changes in the population and forests over the years, Dr. Andy Dietzel from the ARC Centre of Excellence for Coral Reef Studies says few teams have measured coral life. “We measured changes in colony sizes because population studies are important for understanding demography and the corals’ capacity to breed,” the study’s lead author says in a media release.

Three decades of devastation along Great Barrier Reef

The study looked at coral communities and their colony sizes along the entire Great Barrier Reef between 1995 and 2017. The results find a growing shortage of corals of all sizes which contribute to underwater life. Researchers add recent temperature shifts have caused significant damage to this ecosystem.

“We found the number of small, medium and large corals on the Great Barrier Reef has declined by more than 50 percent since the 1990s,” says co-author Prof. Terry Hughes. “The decline occurred in both shallow and deeper water, and across virtually all species — but especially in branching and table-shaped corals. These were the worst affected by record-breaking temperatures that triggered mass bleaching in 2016 and 2017.”

Study authors explain that branching and table-shaped corals provide vital structures for fish who live in these reefs. The loss of coral means the loss of habitats. All of this leads to smaller fish populations and less productivity in coral reef fisheries.

Greenhouse gases are threatening coral survival

Dr. Dietzel says, just like the rest of life, coral reefs breed and grow their populations too.

“A vibrant coral population has millions of small, baby corals, as well as many large ones — the big mamas who produce most of the larvae,” Dietzel explains. “Our results show the ability of the Great Barrier Reef to recover — its resilience — is compromised compared to the past, because there are fewer babies, and fewer large breeding adults.”

To make sure the ocean’s reefs don’t disappear, researchers add more data collection on changing trends among coral groups in needed. The study finds climate change continues to drive the growing number of reef disturbances, including marine heatwaves. Along with mass coral bleaching events in 2016 and 2017, record-breaking temperatures in 2020 may have damaged the southern part of the reef as well.

“We used to think the Great Barrier Reef is protected by its sheer size, but our results show that even the world’s largest and relatively well-protected reef system is increasingly compromised and in decline,” Prof Hughes says.

“There is no time to lose — we must sharply decrease greenhouse gas emissions ASAP,” the team concludes.

The study appears in the journal Proceedings of the Royal Society B.

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