The world’s coral reefs are experiencing the worst bleaching event on record, with more than 80% of reefs affected globally, scientists warn. This unprecedented event, which began in January 2023, has devastated reefs across the Pacific, Atlantic, and Indian Oceans, with heat levels high enough to turn corals white.
According to the latest data from Coral Reef Watch, at least 82 countries and territories have witnessed severe coral bleaching, a consequence of record-high ocean temperatures. Reefs are often called the “rainforests of the sea” because they support a third of marine species and are vital to around a billion people worldwide. However, these vital ecosystems are being destroyed by intense ocean heat.
In the ongoing fourth global bleaching event, 84% of reefs have been exposed to harmful heat levels. This is a significant increase compared to previous bleaching events, such as the 68% exposure during the third event (2014-2017), and 37% in 2010. Even coral reefs once considered refuges from ocean heat are no longer safe. Dr. Derek Manzello, director of Coral Reef Watch, noted that these areas, like Raja Ampat and the Gulf of Eilat, are now affected by bleaching, signaling that no reef is immune from the impacts of rising ocean temperatures.
Australia’s Great Barrier Reef, the world’s largest reef system, has faced its sixth widespread bleaching event in just nine years. Similarly, Western Australia’s Ningaloo Coast and other World Heritage-listed reefs are also experiencing unprecedented levels of heat stress.
Bleaching has also affected reefs in Madagascar, South Africa, and other parts of the Indian Ocean. Dr. Britta Schaffelke from the Australian Institute of Marine Science emphasized the event’s scale, noting that “reefs have not encountered this before,” and monitoring efforts are struggling to keep pace with the extent of the damage. She also highlighted the emotional toll on those who work closely with reefs, as they witness irreversible changes.
The Global Coral Reef Monitoring Network (GCRMN) is preparing a report to assess the full impact of this ongoing event, but scientists warn that even this assessment may not capture the full extent of the damage.
In the northern hemisphere, record ocean temperatures caused significant bleaching during the summer of 2023, with coral loss reported across Florida, the Caribbean, and Mexico. In some areas, up to 93% of corals were lost. In the Indian Ocean’s Chagos Islands, nearly a quarter of corals died due to extreme heat. Researchers have described “graveyards of dead corals” in places like the Great Barrier Reef, where one area lost 40% of its corals during early 2024 bleaching.
In response to the extreme heat, Coral Reef Watch added three new threat levels to its global bleaching alert system. Melanie McField, founder of the Healthy Reefs for Healthy People initiative in the Caribbean, described the eerie silence of bleached reefs, saying it’s like “a silent snowfall” has descended, with vibrant fish and colors replaced by a stark, ashen stillness.
Scientists like Dr. Lorenzo Álvarez-Filip have witnessed the devastating effects of bleaching in the Mexican Caribbean, where key reef-building corals have died in just weeks. The loss of these corals, crucial for coastline protection and marine life, is especially painful for those who have studied them for years.
Dr. Valeria Pizarro, a senior coral scientist in the Bahamas, saw dramatic bleaching in July 2023. Shallow reefs, including those used for restoration projects, turned white as staghorn corals and other species perished quickly.
Pizarro emphasized that urgent action is needed to combat climate change. “World leaders need to commit to reducing fossil fuels and investing in clean energy,” she said. “We need real action, not just promises.”
The current crisis highlights the urgent need for global commitment to address climate change and protect the world’s coral reefs, which are teetering on the brink of collapse.
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