One of the world’s greatest natural wonders has suffered greatly as a result of record ocean heat, with coral bleaching on Australia’s Great Barrier Reef reaching “catastrophic” levels, according to a new research.
The most “severe and widespread bleaching” to have hit the region killed over half of the damaged corals observed near an island in the south of the reef last year, according to a group of Australian scientists.
The reef had its most disastrous summer ever in 2024. Record-breaking sea temperatures led to the seventh mass bleaching incident on the reef. When corals are stressed by maritime heat waves, they expel algae from their tissue, giving them a bleached white appearance.
The burning of fossil fuels that warm the world is the cause of the rise in global temperatures. The El Niño weather trend, which raises ocean temperatures in this region of the world, also hastened coral deterioration last year.
Over the course of five months last year, starting at the height of the heat wave in early February, researchers from the University of Sydney monitored 462 coral colonies at the reef’s One Tree Island.
According to the peer-reviewed study that was published in Limnology and Oceanography Letters, 370 of those colonies had bleached by May, and by July, 52% of the bleached corals had died.
Researchers saw the beginning of “colony collapse,” in which the dead skeleton separates from the reef and turns into rubble, in certain coral species that had a 95% death rate.
Black band disease, which infiltrates coral tissue and has the potential to destroy it, infected another species, the goniopora.
Lead author Maria Byrne of the university’s School of Life and Environmental Sciences stated, “Our findings underscore the urgent need for action to protect coral reefs, which are not only biodiversity hotspots but also crucial for food security and coastal protection.”
According to Byrne, the study location is located in a protected section of the reef, far from the coast, and unaffected by tourism or mining.
The reef, however, “despite its protected status, was not immune to the extreme heat stress that triggered this catastrophic bleaching event,” she said.
Almost 133,000 square miles (345,000 square kilometers) in size, the Great Barrier Reef is the largest coral reef in the world and is home to 411 hard coral species and over 1,500 fish species. It makes billions of dollars in economic contributions to Australia year, mostly from tourism, and is aggressively marketed to tourists from other countries as one of the greatest natural marvels in the world.
Mass bleaching, according to the authors, is turning into “a biennial event,” which “reinforces the need for urgent global action now to adhere to ambitious climate and reduced emissions targets.”
The study discovered sickness and death in coral species thought to be hardy, and the bleaching affected parts of the reef that had not previously been affected.
“Seeing the impacts on a reef that has largely avoided mass bleaching until now is devastating,” according to marine scientist and study co-author Shawna Foo. “The high rates of mortality and disease, particularly in such a remote and pristine area, highlight the severity of the situation.”
CNN reported in February of last year that five distinct reefs in the northern and southern regions of the delicate but ecologically significant site were bleached.
Prior reports of severe mass bleaching in the Great Barrier Reef date back to 1998, 2002, 2016, 2017, 2020, and 2022.
There are significant worries for the reef’s future because the bleaching in 2022 was the first to occur during a La Niña period, which is El Niño’s counterpart and typically has a cooling effect.
The study’s ramifications go beyond ecology and conservation to populations who rely on the reef for fishing, tourism, and coastal protection, the authors said, making it a “wake-up call for policymakers and conservationists.”
According to Ana Vila Concejo, a co-author of the study from the university’s School of Geosciences, “the resilience of coral reefs is being tested like never before, and we must prioritize strategies that enhance their ability to withstand climate change,”
“Our findings underscore the need for immediate and effective management interventions to safeguard these ecosystems.”
