The southern Great Barrier Reef is suffering extensive coral bleaching due to heat stress, the reef’s managers said on Wednesday, raising fears that a seventh mass bleaching event could occur across the vast, ecologically important area.
An aerial survey conducted last weekend by the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science found that the bleaching was “extensive and fairly uniform across all reefs surveyed.”
The teams flew over 27 coastal reefs in the Keppel Islands and Gladstone region and 21 offshore reefs in the Capricorn Bunkers off the coast of southern Queensland last weekend.
Dr. Mark Read, the authority’s director of reef health, said most coral surveyed “showed some degree of bleaching with white and fluorescent colonies observed in shallow reef areas.”
Covering an area of almost 345,000 square kilometers, the Great Barrier Reef is the world’s largest coral reef, home to more than 1,500 species of fish and 411 species of hard corals. It contributes billions of dollars to the Australian economy every year and is heavily promoted to foreign tourists as one of the country’s – and the world’s – great natural wonders.
But rising ocean temperatures are causing destructive reef bleaching, while the world continues to burn planet-warming fossil fuels. Ocean temperatures are also getting hotter under the current El Niño – a natural climate pattern that produces warmer-than-average sea surface temperatures – which is one of the strongest on record.
Bleaching occurs when stressed coral sheds algae from its tissue, depriving it of a food source. If water temperatures remain higher than normal for too long, coral can starve and die, turning white as the carbonate skeleton is exposed.
Great Barrier Reef managers plan to expand air and water surveys across the entire reef in the coming weeks. Although the southern part of the reef has been worst affected, the reef authority has received reports of bleaching from all other regions of the marine park.
“Aerial surveys are an ideal tool to assess the spatial extent of the bleaching, but we need to go underwater to understand more about the severity of the bleaching and how deep the bleaching extends,” says Dr. Neal Cantin, senior researcher at the Australian Institute of Marine Sciences.
A CNN team visiting the Great Barrier Reef two weeks ago observed bleaching at the southernmost coral bay, Lady Elliot Island, and on four different outer reefs near Cairns, in the middle part 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 summer average.
“I’ve been working on these reefs for almost 20 years and I’ve never felt the water so warm,” said Dr. Maya Srinivasan, a scientist at the university’s Center for Tropical Water and Aquatic Ecosystem Research, said in a statement last week. .
“Once we got in the water, we could immediately see parts of the reef that were completely white due to severe bleaching. Some corals were already dying.”
Fear of the seventh massacre
Scientists say corals can recover if ocean temperatures stabilize.
“We have seen fish abundance decrease as coral cover decreases in this region due to previous impacts like this. But we have also seen the recovery of coral and fish communities on many reef areas – there just needs to be enough time between impacts for this recovery to happen,” said Srinivasan.
Higher ocean temperatures caused severe mass bleaching at 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 counterpart to El Niño, which typically has a cooling impact – raised serious concerns about the reef’s prospects.
There are concerns that a seventh mass bleaching event will occur in 2024.
“While we must wait for official confirmation from the Marine Park Authority, it certainly appears that the seventh mass bleaching event is happening on the Great Barrier Reef, with reports of severe bleaching along its length,” said David Ritter, CEO of Greenpeace Australia Pacific. , told CNN.
“We know the climate crisis is driving marine heat waves and these bleaching events, but the frequency and scale at which they are happening now is frightening – every summer we hold our breath.”
Last year, a record marine heat wave “decimated” coral populations around Florida and the Caribbean, and observers in Australia fear a similar fate awaits the country’s reefs.
“What we’re seeing in Florida and the broader Caribbean is a lesson of what’s going to happen over the next 12 months if we see this happening now,” said Ove Hoegh-Guldberg, climatologist and chief scientist at the Great Barrier Reef Foundation. , recently told CNN.
According to the annual climate report from the US National Oceanic and Atmospheric Administration (NOAA), the warmest year since global records began in 1850, ocean temperatures rose to 37 degrees Celsius in some regions and entire oceans bleached. reefs.
With water temperatures soaring to unprecedented levels, NOAA added three new levels to its warning system earlier this month to account for increasingly severe coral bleaching and higher mortality rates.
Alert Level 5, the new highest level classified as ‘near complete mortality’, means that more than 80% of corals in the flagged area are at risk of dying due to high, prolonged water temperatures.
Last year, the UNESCO World Heritage Committee decided not to add the Great Barrier Reef to its list of sites ‘at risk’, despite scientific evidence pointing to the risk of another mass bleaching event.
Greenpeace’s Ritter said that after the decision, “the Australian government pledged 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 trajectory.”
He added that “claims that Australia takes the health of the Great Barrier Reef seriously ring hollow as we continue to expand and subsidize the coal and gas industries to the tune of billions every year.”
The Labor government has approved four new coal mines or expansions since coming to power in May 2022, according to the Australia Institute’s Coal Mine Tracker.
CNN’s Rebecca Wright and Hilary Whiteman contributed reporting.
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