April 24, 2024

Australia’s Great Barrier Reef suffers ‘extensive’ coral bleaching as scientists fear seventh mass bleaching event


The southern Great Barrier Reef is experiencing extensive coral bleaching due to heat stress, reef managers said Wednesday, raising fears that a seventh mass bleaching event could be occurring across this vast and ecologically important reef. local.

Aerial surveys carried out last weekend by the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science found that bleaching was “extensive and fairly uniform across all reefs surveyed”.

Teams flew over 27 inshore reefs in the Keppel Islands and Gladstone region and 21 offshore reefs in the Capricorn Bunkers off the south coast of Queensland last weekend.

Mark Read, the authority’s director of reef health, said most of the corals surveyed “showed some level of bleaching with white, fluorescent colonies observed in shallow reef areas.”

Covering almost 345,000 square kilometers (133,000 square miles), the Great Barrier Reef is the largest coral reef in the world, home to more than 1,500 species of fish and 411 species of hard coral. It contributes billions of dollars annually to the Australian economy and is heavily promoted to foreign tourists as one of the country’s – and the world’s – greatest natural wonders.

But rising ocean temperatures are fueling the destructive bleaching of reefs as the world continues to burn planet-warming fossil fuels. Ocean temperatures are also becoming even warmer under the current El Niño – a natural climate pattern that causes warmer-than-average sea surface temperatures – which is one of the strongest on record.

Bleaching occurs when stressed coral ejects algae from within its tissue, depriving it of a food source. If the water temperature remains above normal for too long, the coral can starve and die, turning white as its carbonate skeleton is exposed.

Jonas Gratzer/LightRocket/Getty Images

Dead coral found on Lady Elliot Island off the coast of Queensland, Australia on October 10, 2019.

Great Barrier Reef managers plan to extend aerial and water surveys across the reef in the coming weeks. Although the southern part of the reef is most affected, the reef authority has received reports of bleaching from all other regions of the marine park.

“Aerial surveys are an ideal tool for assessing the spatial extent of bleaching, but we need to dive underwater to understand more about the severity of bleaching and the depth of bleaching,” said Dr. Neal Cantin, senior research scientist at the Australian Institute of Marine Sciences.

A CNN team that visited the Great Barrier Reef two weeks ago observed bleaching on the southernmost coral islet, Lady Elliot Island, and on four different outer reefs off Cairns in the middle section of the reef.

And a separate report from a team at James Cook University reported areas of moderate to severe coral bleaching around the Keppel Islands, where water temperatures were well above the summer average.

“I have been working on these reefs for almost 20 years and have never felt the water as warm as this,” said Dr. Maya Srinivasan, a scientist at the university’s Tropical Waters and Aquatic Ecosystems Research Center, in a statement last week. .

“When we entered the water, we could instantly see parts of the reef that were completely white due to severe bleaching. Some corals were already dying.”

Scientists say corals could recover if ocean temperatures stabilize.

“We have seen fish abundance decline as coral cover decreases in this region following past impacts like this. But we have also seen the recovery of coral and fish communities in many reef areas – there just needs to be enough time between impacts to allow this recovery to occur,” said Srinivasan.

Warmer ocean temperatures caused severe mass bleaching on the Great Barrier Reef in 2016, 2017 and 2020. Previous bleaching occurred in 1998 and 2002.

Another bleaching event in 2022 – the first during a La Niña event, the equivalent of El Niño, which tends to have a cooling influence – has raised serious concerns about the reef’s prospects.

There are concerns that in 2024 there will be a seventh mass bleaching event.

“While we must await official confirmation from the Marine Park Authority, it certainly appears that the seventh mass bleaching event is taking place on the Great Barrier Reef, with reports of severe bleaching occurring along its length,” David Ritter, CEO of Greenpeace Australia Pacific, told CNN.

“We know that the climate crisis is causing marine heatwaves and leading to these bleaching events, but the frequency and scale at which they are occurring now is frightening – every summer we hold our breath.”

A record marine heat wave “decimated” coral populations around Florida and the Caribbean last year and observers in Australia fear a similar fate could be in store for the country’s reefs.

“What we’re seeing in Florida and the Caribbean is a lesson in what’s going to happen over the next 12 months as we see this thing happening now,” said Ove Hoegh-Guldberg, climatologist and chief scientist at the Great Barrier Reef Foundation. , he recently told CNN.

Last year, the hottest year since global records began in 1850, according to the US National Oceanic and Atmospheric Administration’s (NOAA) annual climate report, ocean temperatures rose to 37 degrees Celsius (100 degrees Fahrenheit). in some regions and the bleaching of entire reefs.

With water temperatures rising to unprecedented levels, NOAA earlier this month added three new levels to its warning system to account for increasingly severe coral bleaching and higher mortality rates.

Alert level 5, the new highest level classified as “almost complete mortality”, means that more than 80% of corals in the highlighted area are at risk of dying due to long-lasting high water temperatures.

Last year, UNESCO’s World Heritage Committee decided not to add the Great Barrier Reef to its list of “in danger” sites, despite scientific evidence suggesting the risk of another mass bleaching event.

Greenpeace’s Ritter said that following the decision, “the Australian government promised to do everything it could to protect the Great Barrier Reef. This must include addressing climate change as an existential threat to the reef and ensuring our emissions reduction plans are aligned with a 1.5 degree pathway.

He added that “claims that Australia is serious about the health of the Great Barrier Reef ring hollow when we continue to expand and subsidize the coal and gas industry worth billions every year.”

According to the Australia Institute’s Coal Mine Tracker, the Labor government has approved four new coal mines or expansions since coming to power in May 2022.

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