NOAA, ICRI confirm fourth global mass coral bleaching event in 2023-2024

GS Paper III

News Excerpt:

The world is experiencing its fourth global coral bleaching event, with significant bleaching documented across major ocean basins since February 2023.

More About the News: 

  • The National Oceanic and Atmospheric Administration’s (NOAA) Coral Reef Watch (CRW) and the International Coral Reef Initiative (ICRI) have verified the occurrence of the fourth global mass coral bleaching event spanning 2023-2024. 
  • This alarming event encompasses bleaching incidents across 53 countries, territories, and local economies across five ocean basins from February 2023 to April 2024. 
  • This is the Second such event in the past 10 years coming at a time when the ocean temperatures have recorded an unprecedented high which indicates a concerning trend of increasing frequency and severity.

Extent of Bleaching: 

  • Coral bleaching has been confirmed in at least 53 countries, territories, and local economies across the Atlantic, Pacific, and Indian Oceans. 
  • Regions affected include Florida (U.S.A), the Caribbean, the Eastern Tropical Pacific, Australia's Great Barrier Reef, the South Pacific, the Red Sea, the Persian Gulf, and the Gulf of Aden.

Impacts of Bleaching: 

  • Coral bleaching can lead to coral mortality, negatively impacting economies, livelihoods, food security, and ecosystem services provided by coral reefs.

Resilience and Recovery: 

  • While bleaching can result in coral death, corals can recover if the stress driving the bleaching diminishes. 
  • Resilience-based management practices and coral restoration efforts are crucial for aiding coral recovery and maintaining biodiversity.

Global Action and Management: 

  • International organizations like the International Coral Reef Initiative (ICRI) and NOAA are leading efforts to apply resilience-based management actions, develop best practices, and implement interventions for coral reef conservation and restoration. 
  • This includes deploying recommended interventions during heat stress events and incorporating resilience-based management practices into strategic plans.

Need for Monitoring and Cooperation: 

  • Regular monitoring of coral reef ecosystems is essential for assessing impacts, tracking recovery, and identifying areas that may require further protection or intervention. 
  • Global networks such as the Global Coral Reef Monitoring Network and the US Coral Reef Task Force facilitate reporting and cooperation on coral bleaching events.

Coral Bleaching Hub: 

  • ICRI has developed the Coral Bleaching Hub to share key messages, resources, and solutions related to coral bleaching, fostering global cooperation and informing policy and planning efforts.

Hard corals, distinct from soft corals, are marine organisms encased in a tough shell. They engage in a symbiotic relationship with single-celled algae, which reside on their shells, imparting them with vibrant colors.

Key Concepts: 

  • Coral Bleaching:
    • These corals form colonies and intricate structures known as coral reefs, serving as habitats for myriad marine life forms. 
      • Approximately 25% of marine species rely on coral reefs at various stages of their life cycles. 
    • However, when ocean temperatures rise, the algae on corals undergo die-off, causing the corals to turn white—a phenomenon known as "bleaching." 
      • Bleached corals become susceptible to diseases and eventual mortality, posing grave risks to marine ecosystems. 
    • Yet, with effective management and adaptation measures, corals can potentially recover their health.
  • Impact of Ocean Heatwaves and Environmental Stressors: 
    • The threat to coral reefs intensifies amidst escalating sea surface temperatures and prolonged marine heatwaves, compounded by factors like ocean acidification and pollution. 
    • Marine heatwaves entail extensive areas of sea and ocean surfaces experiencing heightened temperatures for extended durations, exacerbating stress on coral ecosystems. 
    • The year 2023 witnessed record-breaking heat levels in both the atmosphere and oceans, with marine heatwaves significantly impacting vital ecosystems and food systems worldwide. 
    • The prevalence of El Niño conditions in the equatorial Pacific Ocean further contributed to elevated ocean temperatures, exacerbating the warming trend observed over land and seas.
  • Link Between El Niño Events and Coral Bleaching: 
    • The occurrence of El Niño events correlates closely with ocean heating and mass coral bleaching. 
      • Since 1950, instances of El Niño events have often preceded periods of mass coral bleaching, with the second year of El Niño cycles typically experiencing heightened ocean temperatures and bleaching events. 
    • Moreover, localized coral bleaching has been observed during La Niña years, underscoring the broader impact of oceanic warming on coral reef ecosystems.
  • Future Projections and Management Strategies: 
    • Climate models project a grim outlook for coral reefs, with bleaching events anticipated to escalate in severity, frequency, and magnitude. 
      • Experts warn that by mid-century, annual bleaching occurrences may become commonplace for most reefs. 
    • Long-term data on coral reef conditions are crucial for contextualizing such events, enabling quantification of coral mortality, tracking recovery trajectories, and identifying areas necessitating additional protection or intervention through innovative measures.


  • The International Coral Reef Initiative (ICRI): 
    • The International Coral Reef Initiative (ICRI) is a global partnership between Nations and organizations which strives to preserve coral reefs and related ecosystems around the world. 
    • It is an informal group whose decisions are not binding on its members but the work of ICRI is regularly acknowledged in United Nations documents, highlighting the Initiative’s important cooperation, collaboration and advocacy role within the international arena.
    • The Initiative was founded in 1994 by eight governments: Australia, France, Japan, Jamaica, the Philippines, Sweden, the United Kingdom, and the United States of America. 
    • It was announced at the First Conference of the Parties of the Convention on Biological Diversity in December 1994, and at the high level segment of the Intersessional Meeting of the U.N. Commission on Sustainable Development in April 1995. 
    • ICRI now has over 100 members.
    • ICRI’s objectives are to:
      • Encourage the adoption of best practice in sustainable management of coral reefs and associated ecosystems
      • Build capacity
      • Raise awareness at all levels on the plight of coral reefs around the world.
  • Coral Reef Watch (CRW): 
    • Coral Reef Watch (CRW) is a program established by the National Oceanic and Atmospheric Administration (NOAA) to monitor, predict, and provide early warnings about threats to coral reef environments worldwide. 
    • It utilizes a combination of satellite data, modeling, and in-situ observations to track environmental conditions and assess the health of coral reefs in near real-time. 
    • CRW's primary focus is on detecting and predicting coral bleaching events. 
    • By providing alerts and warnings about impending bleaching events, CRW helps coral reef managers, policymakers, researchers, and other stakeholders take proactive measures to mitigate the impacts of bleaching and other threats.


The current trajectory underscores the urgent need for concerted global efforts to mitigate the impacts of climate change and preserve coral reef ecosystems for future generations. Effective monitoring, management, and intervention strategies are imperative to safeguarding these invaluable marine habitats and the myriad species reliant upon them.

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