The planet’s corals are currently experiencing the largest mass bleaching event ever recorded due to high ocean temperatures, a U.S. government agency warned on Friday.
This climate change-related phenomenon, which threatens the survival of biodiversity-rich reefs, now affects more than two-thirds of corals in the Atlantic, Pacific, and Indian Oceans.
Fourth event in 26 years
“The planet is currently in the midst of the largest bleaching event ever recorded,” said Derek Manzello, coordinator of the coral program at the U.S. Oceanic and Atmospheric Administration (NOAA), in a statement to AFP.
The ongoing event is the fourth since 1998. “Between January 1, 2023, and October 10, 2024, approximately 77% of the world’s coral reefs experienced thermal stress at levels consistent with bleaching,” he added in an email. “This percentage is still increasing.”
The unusual heat stresses the corals, causing them to expel their zooxanthellae—algae that live in symbiosis with them and provide essential nutrients. Without these algae, corals lose their color and risk dying.
Following two events in 1998 and 2010, the previous record was set between 2014 and 2017, during which 65.7% of the world’s coral reefs were affected. “We have therefore surpassed the previous record by 11.3% in half the time. This percentage is still on the rise,” added Derek Manzello.
Corals: Vital organisms for humanity
NOAA has received confirmed reports of bleaching events in 74 countries or territories across both the Northern and Southern Hemispheres. Approximately 850 million people worldwide rely on coral reefs for their livelihoods and food. Reefs, which host highly rich and diverse ecosystems, also protect coastlines from storms and erosion, according to the NGO WWF.
An accelerating pace
The rate of ocean warming has nearly doubled since 2005, according to a report from the European Copernicus Observatory published at the end of September. This phenomenon is accompanied by a surge in marine heatwaves. In 2023, 22% of the world’s oceans experienced at least one severe or extreme heatwave. This warming is attributed to the fact that oceans have absorbed more than 90% of the excess heat from the climate system since 1970, caused by massive greenhouse gas emissions from humanity, according to the IPCC.
Source: la1ere
