The U.S. National Oceanic and Atmospheric Administration (NOAA) said on Monday that coral reefs around the world are experiencing a fourth mass bleaching event, turning the reefs a ghostly white color. A report from the agency said bleaching could impact economies, ecosystems and livelihoods around the world.

Since February 2023, more than 54 countries and regions have experienced severe coral bleaching, and the recently announced global coral bleaching is the second in 10 years.

Bleaching threatens corals when temperature changes cause them to excrete the nutrient-rich algae that keeps them alive from their tissues. Many bleaching events, such as this one and three previous ones, coincide with El Niño weather patterns or warming ocean temperatures.

While coral bleaching has become increasingly common, it is considered “global” only if it occurs in every major ocean basin on Earth over a 365-day period, including the Atlantic, Pacific and Indian oceans.

“As the world’s oceans continue to warm, coral bleaching is becoming more frequent and severe,” said Derek Manzello, NOAA’s Coral Reef Watch coordinator, which monitors heat stress. ”

According to Reuters, the global bleaching event may be the worst yet.

“In some reefs, everything you see when you dive is white,” said marine ecologist Lorenzo Alvarez-Philippe of the National Autonomous University of Mexico.

Alvarez-Philippe added that bleached corals have the potential to recover if seawater cools, but some Caribbean corals have died despite falling winter temperatures.

“This global event requires global action,” NOAA said in a statement, adding that the agency, along with other international stakeholders, was helping “advance coral intervention and restoration in the face of climate change.” .

This report contains information from Reuters, the Associated Press and AFP.