More than 80% of the world’s coral reef areas have been exposed to the worst mass bleaching event on record, spurred by record high ocean temperatures that have spread like an underwater wildfire over corals across the Pacific, Atlantic and Indian oceans.
According to the new report released by the International Coral Reef Initiative and data from the U.S. National Oceanic and Atmospheric Administration which track reef health, reefs in at least 82 countries and territories have been exposed to enough heat to turn corals white since the global event started in January 2023.
Heat stress causes corals to expel the symbiotic algae that live in their tissues and lose their vibrant colours and vital nutrients in the process. Last year was the hottest on record and the first to reach over 1.5 degrees Celsius warmer than pre-industrial times, contributing to unprecedented ocean temperatures and triple the previous record number of marine heatwaves around the world.
Unprecedented scale of destruction
Even reefs considered by scientists to be refuges from the ocean’s rising levels of heat have been bleached, Dr Derek Manzello, the director of Coral Reef Watch, said. The bleaching event has been so severe that NOAA’s Coral Reef Watch program had to add levels to its bleaching alert scale to account for the growing risk of coral death.
It marks the fourth global bleaching event since 1998 and has now surpassed bleaching from 2014-17 that hit around two-thirds of reefs, said the ICRI, a mix of more than 100 governments, non-governmental organizations and others. Its reportedly not clear when the current crisis will end.
Melanie McField, the founder of the Healthy Reefs for Healthy People initiative in the Caribbean, said reefs had fallen quiet across the world: “Bleaching is always eerie – as if a silent snowfall has descended on the reef … there is usually an absence of fluttering fish and an absence of the vibrant colours on the reef … It’s an ashen pallor and stillness in what should be a rowdy vibrant reefscape.”
“We may never see the heat stress that causes bleaching dropping below the threshold that triggers a global event,” said Mark Eakin, executive secretary for the International Coral Reef Society and retired coral monitoring chief for the US National Oceanic and Atmospheric Administration. “We’re looking at something that’s completely changing the face of our planet and the ability of our oceans to sustain lives and livelihoods,” Eakin said.
Conservation efforts underway
Efforts are underway to conserve and restore coral. One Dutch lab has worked with coral fragments, including some taken from off the coast of the Seychelles, to propagate them in a zoo so that they might be used someday to repopulate wild coral reefs if needed. Other projects, including one off Florida, have worked to rescue corals endangered by high heat and nurse them back to health before returning them to the ocean.
Scientists at the Woods Hole Oceanographic Institution have discovered that broadcasting recordings of vibrant reef sounds to damaged coral encourages marine life, and even coral larvae, to return. In Caribbean trials, underwater speakers playing healthy-reef audio boosted coral larval settlement by 70% on average, and in some spots by as much as 700%, compared to silent controls.
Government inaction would be “the kiss of death”.
However, scientists warn conservation efforts alone will not be enough to reverse the damage done by record temperatures. It is essential to reduce greenhouse gas emissions that are the root cause of climate change, such as carbon dioxide and methane, as “everything else is looking more like a Band-Aid rather than a solution,” Eakin said.
US President Donald Trump has moved aggressively in his second term to boost fossil fuels and roll back clean energy programs, which he says are necessary for economic growth. “I think people really need to recognise what they’re doing … inaction is the kiss of death for coral reefs,” said Melanie McField.