World’s Fourth Mass Coral Bleaching Event Likely Ended in 2025

By nesdis.noaa.gov, nesdis.noaa.gov.

After analyzing satellite data and bleaching observations, NOAA’s experts say the record-breaking fourth global coral bleaching event likely concluded in mid-2025.

The fourth global coral bleaching event was confirmed by NOAA on April 15, 2024. From early-2023 to mid-2025, bleaching-level heat stress impacted 84% of the world’s coral reef area in all three coral reef-containing ocean basins (Pacific, Atlantic and Indian Oceans). Mass bleaching was documented in at least 83 countries and territories.

Following the severe bleaching in Western Australia in early 2025, global heat stress has been in decline and there have been only isolated reports of coral bleaching. The Western Australia bleaching event likely bookended the fourth global event.

“We needed to confirm that no widespread, large-scale bleaching was reported anywhere during the austral summer which ran from December 2025 through February 2026, before we were confident the event had ended,” said Derek Manzello, Coordinator of NOAA’s Coral Reef Watch. “We are now in the era where reefs will bleach on a near-annual basis, which means defining when global events begin and end is becoming increasingly difficult. The plan moving forward is to rely on field bleaching observations to determine if and when global events are happening.”

This news comes during National Ocean Month and a day after World Reef Awareness Day on Monday. Both events are designed to focus the public’s attention on the importance of a healthy ocean. Coral reefs are a window into ocean health. Coral reefs provide coastal protection from waves, biodiversity support for ocean species, and economic opportunities for communities in tourism and fisheries.

Coral bleaching at Cheeca Rocks in the Florida Keys in 2023. [Credit: NOAA]