World’s Coral Reefs Face Historic Bleaching Crisis

Why in the News ?

The International Coral Reef Initiative confirmed a global coral bleaching event, the worst on record, affecting 84% of coral reefs worldwide since 2023 due to rising ocean temperatures. It’s the fourth event since 1998.

Unprecedented Global Bleaching Impact:

  • The fourth global bleaching event since 1998 began in 2023.
  • It now impacts 84% of the world’s coral reefs, surpassing the 2014-17 bleaching that affected two-thirds of reefs.
  • This mass bleaching is driven by sustained ocean warming.
  • The International Coral Reef Initiative (ICRI), comprising over 100 global entities, issued the alert.

Key Drivers and Consequences

  • 2023 was Earth’s hottest year; ocean temperatures away from poles averaged 87°C – a record high.
  • Corals bleach when prolonged heat stress expels their symbiotic algae, essential for their survival.
  • Mark Eakin, ICRI executive, warned that oceans may not cool enough again to prevent continuous bleaching.
  • Coral bleaching reduces marine biodiversity, as 25% of marine species rely on coral ecosystems.

Coral Reefs: Ecological and Economic Role

  • Known as the “rainforests of the sea”, coral reefs support diverse marine life.
  • They are vital for seafood production, tourism, and coastal protection against erosion and storms.
  • Continued bleaching threatens livelihoods and the ecological balance of ocean ecosystems globally.

Fourth Global Coral Bleaching Event – Key Facts

Extent and Impact

● 77% of global coral reef areas across Atlantic, Pacific, and Indian Oceans affected by bleaching-level heat stress.
● NOAA declared the fourth global bleaching event in 2024 (earlier: 1998, 2010, 2014–2017).
● Mass bleaching events documented on the Great Barrier Reef in 1998, 2002, 2016, 2017, 2020, 2022, and 2024.
● Prior record (2014–2017) affected 66% of reef area globally.

What Are Corals?

● Invertebrates from phylum Cnidaria; made of polyps secreting calcium carbonate skeletons.
●Zooxanthellae algae give corals their vibrant colors.
●Types: Fringing, Barrier reefs, and Atolls.
●Provide habitat to 25% of marine life; support 1+ billion people globally.

Coral Bleaching

● Occurs when algae are expelled due to stress (mainly warming).
●Not dead, but vulnerable; recovery requires cooler temperatures.
●Bleaching worsened by El Niño and climate change.
●Scientists fear reefs may have crossed a tipping point at just 1.3°C warming.