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Coral reef area hit by bleaching-level heat stress in the fourth global bleaching event

The share of the world's coral reef area that experienced heat stress high enough to cause bleaching between 1 January 2023 and 30 September 2025, the fourth global coral bleaching event, as published by NOAA Coral Reef Watch. Heat stress measures the risk of bleaching, not observed bleaching or coral death.

Latest value

84.4%

World (coral reef areas in Coral Reef Watch's global 5 km satellite products), 1 January 2023–30 September 2025. Version Status update of 2 June 2026.

As published

“From 1 January 2023 to 30 September 2025, bleaching-level heat stress has impacted ~84.4% of the world's coral reef area and mass coral bleaching has been documented in at least 83 countries and territories.”

NOAA Coral Reef Watch coral bleaching heat stress and global bleaching status, Current Global Bleaching: Status Update (Updated: June 2, 2026), first paragraph under the headline. Checked word for word against the stored copy of the document every time the data is rebuilt.

Where it comes from

Producer
NOAA NESDIS Center for Satellite Applications and Research, Coral Reef Watch · NOAA Coral Reef Watch coral bleaching heat stress and global bleaching status
Version
Status update of 2 June 2026
File
https://coralreefwatch.noaa.gov/satellite/research/coral_bleaching_report.php
Fetched
2026-10-04 (automatically), 25,234 bytes
Fingerprint
sha256 d48ccb9c370ee02e46c5db311665f9a7d7f2b1a22d474f08e6fb3018ebd11b13
Copies
No Wayback copy recorded yet.Our copy of the exact file
Cite the producer
NOAA Coral Reef Watch. 2018, updated daily. NOAA Coral Reef Watch Version 3.1 Daily Global 5km Satellite Coral Bleaching Degree Heating Week Product, Jan. 1, 2023-Dec. 31, 2025. College Park, Maryland, USA: NOAA Coral Reef Watch. Data set accessed 2026-10-04 at https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/nc/v1.0/annual/. Skirving, W; Marsh, B; De La Cour, J; Liu, G; Harris, A; Maturi, E; Geiger, E; Eakin, CM. CoralTemp and the Coral Reef Watch Coral Bleaching Heat Stress Product Suite Version 3.1. Remote Sens. 2020, 12, 3856; https://doi.org/10.3390/rs12233856.

What was done to it

  1. Quoted from Current Global Bleaching: Status Update (Updated: June 2, 2026), first paragraph under the headline. The quote was found in the visible text of the snapshot (sha256 d48ccb9c370e…) before publishing.

    Code: pipeline/src/envdash/transforms/literature.py · code sha256 a5b5e1344e63f00f… · inputs d48ccb9c370e…

  2. Value: "~84.4%" is published as 84.4 percent of the world's coral reef area for 1 January 2023 to 30 September 2025; the page gives no range.

    Code: pipeline/src/envdash/transforms/literature.py · code sha256 a5b5e1344e63f00f… · inputs d48ccb9c370e…

What it covers

Geography
World (coral reef areas in Coral Reef Watch's global 5 km satellite products)
Basis
Reef area that had bleaching-level heat stress at least once between 1 January 2023 and 30 September 2025, from satellite sea surface temperature (CRW's 5 km Bleaching Alert Area products). The same page gives 68.2% for the third global event (2014–2017). NOAA said on 2 June 2026 that the fourth event likely ended in 2025.
Unit
percent of the world's coral reef area (%)