Fifth mass coral bleaching event in eight years hits Great Barrier Reef, marine park authority confirms | Environment

The Great Barrier Reef is in the grip of a massive coral bleaching event due to global warming – the fifth in just eight years – the government’s marine park agency has confirmed.

The authority, together with scientists from the Australian Institute of Marine Science, has carried out aerial surveys of 300 reefs across two-thirds of the reef, with more to come.

“These studies confirm that a widespread, often massive, coral bleaching event is occurring across the Great Barrier Reef,” the authority said in an update.

Images showing coral bleaching and death at Heron Island from 2021 through February. Photo: CoralWatch

Researchers and scientists told Guardian Australia they were devastated by the bleaching, especially in the southern part of the reef where corals hundreds of years old had been severely bleached.

Dr. Roger Beeden, chief scientist at the Great Barrier Reef Marine Park Authority, said: “We have now seen widespread, often massive, coral bleaching on the reefs surveyed.”

He said the bleaching was caused by global warming and an El Niño climate pattern. In-water surveys were underway to understand the severity of the bleaching, he said, and in the past the reef had shown resilience.

Coral bleaching at Heron Island, Queensland. Photo: CoralWatch

The Great Barrier Reef – the largest coral system in the world – is approximately 2,300 km long, covers an area larger than the size of Italy and consists of approximately 3,000 individual reefs.

The widespread mass bleaching of the Great Barrier Reef was first observed in 1998 and happened again in 2002, 2016, 2017, 2020, 2022 and now in 2024.

Ocean temperatures around the world have been the highest on record for almost a year and the US government’s Coral Reef Watch program has said the planet is on the brink of a fourth global mass coral bleaching event, with reefs in the Atlantic Ocean, the Pacific Ocean and possibly the Indian Ocean, completely bleaching.

The world’s southernmost coral reef, on Lord Howe Island off the Australian coast of New South Wales, is also being hit by bleaching.

In July, the World Heritage Committee will consider whether the reef should be placed on a list of sites “at risk” following concerns about the effects of climate change and pollution and sediment entering the reef’s waters.

Scientists have been warning since the 1990s that as global warming continues, the world’s coral reefs will be among the first ecosystems to be affected.

When corals bleach due to higher-than-average ocean temperatures, they expel the algae that live in them and give them many of their nutrients and color.

When temperatures drop, corals can survive, but scientists say they are more susceptible to disease and struggle to reproduce. In extreme cases of heat stress, corals can die.

Dr. Neal Cantin, senior research scientist at Aims, said: “We now need to combine aerial spatial coverage with in-water surveys to assess the severity of coral bleaching in deeper reef habitats across the different regions of the Marine Park. ”

Coral Bleaching on Lizard Island photo on February 24. Photo: Justin Marshall

According to data from Coral Reef Watch, heat stress on corals in the southern and central regions of the reef is the highest ever recorded, and the second highest in the northern areas.

Diana Kleine, project manager of Coral Watch at the University of Queensland, has been to Heron Island near Gladstone in the south of the reef.

“It’s devastating. Incredible. The water was way too hot. Heron has escaped bleaching several times, but this year it has hit so hard,” she said.

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Coral Watch has observed 4-meter-wide rock corals that take hundreds of years to turn bleached bone white.

Lyle Vail, co-director of the Australian Museum’s Lizard Island Research Station in the reef’s north, said corals began showing heat stress in early February.

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He said: “It’s devastating. Almost all heat-sensitive corals in the shallow waters have bleached.” He said a small number of corals had died.

Environment Minister Tanya Plibersek said: “We know that climate change is the biggest threat to coral reefs worldwide. The Great Barrier Reef is no exception. It is essential that we do everything we can to protect this amazing place for our children and grandchildren.

“We know Australians, especially local communities and businesses along the Reef, will be concerned by this news. The health of the reef is critical for the 64,000 people who depend on it for their jobs, and for the plants and animals that call the reef home.”

She pointed to the government’s statutory target of achieving net zero greenhouse gas emissions by 2050, an enhanced 2030 target and a $1.2 billion investment to help the reef adapt to climate change and improve water quality improve.

WWF-Australia head of oceans Richard Leck said there was particular concern about the southern parts of the reef, which had not been severely bleached since 2016.

“Unless we see a significant drop in temperatures in the coming weeks, the risk of significant coral mortality is high,” he said.

“Five mass bleaching events in eight years show that climate change is putting enormous pressure on the reef.”

He said the federal government must sharply increase its ambitions to reduce greenhouse gas emissions, and Queensland must do more to reduce deforestation.

Dr. Lissa Schindler, reef campaigner at the Australian Marine Conservation Society, said: “This is a huge wake-up call for Australia and the global community that we need to do much more to tackle climate change, which is causing the marine heatwaves that lead to coral bleaching.

“Australia’s current target to reduce carbon pollution by 43% by 2030 is equivalent to a 2 degrees Celsius warming trajectory, which would mean the loss of 99% of the world’s coral reefs.”

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