IN NEWS

Fourth Global Coral Bleaching Event: Over 84% of World’s Coral Reefs Impacted

Introduction

The world is witnessing its fourth global coral bleaching event, confirmed by NOAA and the International Coral Reef Initiative (ICRI) on 15 April 2024. The crisis has intensified rapidly. In May 2024, NOAA reported that more than 60% of the world’s coral reefs had faced bleaching-level heat stress within one year. By 30 March 2025, this figure had risen to 84%, making it the most intense global coral bleaching event ever recorded.The event is closely linked to record-high ocean temperatures, marine heatwaves, El Niño conditions, and human-induced climate change.

ANALYSIS

Why in News?

Coral reefs are in news because the ongoing global bleaching event has affected reefs across 82 countries, territories and economies. Earlier global bleaching events affected 21% of reefs in 1998, 37% in 2010, and 68% during 2014–2017. The ongoing fourth event has already impacted 84% of reefs, showing a sharp rise in the scale and severity of bleaching.The crisis has also affected major reef systems such as the Great Barrier Reef, where scientists recorded the biggest annual decline in live coral cover in two out of three monitored regions since the 1980s.

What is Coral Bleaching?

Coral bleaching occurs when environmental stress, especially excessive ocean heat, forces corals to expel the colourful algae living inside their tissues. These algae provide food and colour to corals. Once expelled, corals turn white.Bleached corals are not immediately dead. They can recover if ocean temperatures return to normal. However, prolonged heat stress weakens corals, increases disease risk and can finally lead to coral death.

Causes of the Current Bleaching Event

The main reason behind the ongoing bleaching event is higher ocean temperature. Climate change, driven by greenhouse gas emissions, has warmed oceans at an alarming rate. The event has also been intensified by the El Niño climate pattern, which pushed ocean temperatures to record highs.The input also highlights that 2024 was among the hottest years, with record-breaking ocean temperatures and a sharp increase in marine heatwaves.

Great Barrier Reef: Major Warning Signal

The Great Barrier Reef suffered its biggest annual drop in live coral since the 1980s. The Australian Institute of Marine Science (AIMS) reported that the early 2024 mass bleaching event was the most widespread and severe on record for the reef.Coral cover declined by:

The northern and southern zones recorded the highest annual declines on record. Scientists warned that repeated bleaching events are coming closer together, reducing the time available for coral recovery.

Coral Reefs and Tipping Point Risk

Coral reefs may reach a tipping point if bleaching events occur too frequently. Recovery becomes difficult when repeated heat stress, cyclones, flooding and other disturbances occur before reefs can rebuild.In the Great Barrier Reef, earlier recovery was mainly supported by fast-growing Acropora corals, but these corals are more vulnerable to heat stress. This makes the reef system more unstable and volatile.

Global Ecological and Economic Importance

Coral reefs are often called the “rainforests of the sea” because they support nearly one-third of known marine life. Around one billion people benefit directly or indirectly from coral reefs.Coral reefs provide:

Climate-change-induced coral loss could cost nearly USD 500 billion annually by 2100.

Coral Bleaching and Global Coral Decline

The Global Coral Reef Monitoring Network (GCRMN), an operational network of ICRI, showed in its Status of Coral Reefs of the World: 2020 report that large-scale bleaching is the greatest disturbance to coral reefs.The 1998 bleaching event alone killed nearly 8% of the world’s coral, while later disturbance events caused a 14% loss of coral from 2009 to 2018.

“Super Corals”: A Ray of Hope

In the remote Pacific atoll of Tatakoto, UNESCO-supported research has identified heat-resistant “super corals”. These corals are surviving extreme ocean temperatures and resisting bleaching during marine heatwaves.The research was led by Laetitia Hédouin, research director at CNRS and coral reef specialist. It was documented by photographer and explorer Alexis Rosenfeld under UNESCO’s “Coral Reefs, a Challenge for Humanity” project.This discovery shows that some coral species may possess natural resilience, but conservation and climate action remain essential.

Way Forward

Coral reef conservation requires both global climate action and local ecosystem protection. Local solutions include reducing pollution, stopping overfishing, coral restoration, selective breeding of heat-resistant corals and strengthening monitoring systems.However, these measures will work only if global warming is limited to as close to 1.5°C as possible. Current climate plans put the world on track for nearly 2.7°C warming, which would seriously threaten coral survival.

NECESSARY STATIC PART

NOAA

ICRI

GCRMN

AIMS

UNESCO

Previous Global Coral Bleaching Events

Updated – 16 May 2024 ; 10:51 PM | Reuters, Updated – 23 April 2025 | ICRI, Updated – 05 August 2025 | The Guardian