SYDNEY, Australia – A wide stretch of the Great Barrier Reef has been hit by a sixth mass bleaching event, the marine parks authority said on Friday, an alarming milestone for the coral wonder that points to the ongoing threat from climate change and greenhouse gas emissions.
Government scientists using helicopters and small planes to survey 750 individual reefs hundreds of miles last week found severe bleaching in 60 percent of the coral.
Bleaching events have now occurred in four of the last seven years, with 2022 offering an unsettling first — a mass bleaching in a year of La Niña when more rain and cooler temperatures should offer sensitive corals a moment of calm to recover.
“We see that coral reefs cannot cope with the current rate of warming and frequency of climate change,” said Dr. Neal Cantin, a coral biologist who led one of the teams monitoring the reef’s health. “We need to slow this rate of warming as quickly as possible.”
Coral bleaching is often referred to as a climate change warning system, a canary in a struggling earth’s coal mine. It suggests that corals are severely stressed by the steadily warming water around them. Last year, scientists recorded the hottest year on record for the world’s oceans – for the sixth straight year.
First, stress on coral reefs shows up in bright, almost neon colors as the coral, which is an animal, expels the algae that live within it, providing the coral with food. Corals turn bone white but can still recover if temperatures cool long enough.
However, scientists report that this has become increasingly rare. Between 2009 and 2019, according to a comprehensive study last year, 14 percent of the world’s coral reefs were lost.
Along the 1,500 miles of the Great Barrier Reef – a stunning ecosystem that can be seen from space – there are still large stretches of healthy coral teeming with sharks, turtles, rays and pencil-colored fish.
But along the natural wonder there are also traces of damage. The blocks of underwater graveyards, gray patches of brittle dead coral covered in ugly shreds of seaweed, have grown with every mass bleaching since the first occurred in 1998.
In Australia, this decline has become increasingly politicized. Prime Minister Scott Morrison’s government, which has done little to reduce the country’s dependence on fossil fuels or exports, has repeatedly urged the United Nations to ignore its own scientific advice and prevent the reef from being listed of endangered world heritage sites.
Rather than aggressively pursuing emissions cuts, Australia has poured hundreds of millions of dollars into long-term projects aimed at helping the reef by eliminating agricultural runoff, killing invasive species, or finding and cultivating the most heat-resistant coral species.
Climate protests across the country have also intensified, some led by children, others by activists who have tried to block trains and traffic.
UN scientists are now in Australia to check the condition of the reef. dr Cantin said he met with them Friday afternoon and explained to them what the polls had found.
The reef’s image (and Australia’s responsibility for it) will be seriously tarnished if the UN suggests it is slowly approaching extinction. But the damage to the world’s reefs goes far beyond threatening tourism or a country’s reputation.
Although coral reefs cover a tiny fraction of the ocean floor, they support an estimated $2.7 trillion in goods and services worldwide every year, according to a recent report by the International Coral Reef Initiative. Their fish provide food for hundreds of millions of people around the world – and in Australia and elsewhere they provide shelter from the severe storms that are also becoming more frequent with climate change.
dr Cantin said he was particularly disappointed with the spatial footprint of this year’s bleach damage. Reefs closer to shore experienced the most extreme bleaching, but he said the bleaching appears to have covered a larger area than back-to-back eruptions in 2016 and 2017.
He said it was the product of a summer that started early.
“In December we were already warmer than the historic summer highs in February,” he said. There was a cooldown in February, he added, but the last two weeks of this month saw little rain and persistent heat.
“With the frequency of big, stressful summers, we’ve been on pale watch almost every year,” he said. “We are in worrying times.”