Over 80% of world's coral reefs hit by longest bleaching occurrence

Eighty-two countries, territories, economies suffering damage, says preservation group

- David Fogarty

The world's coral reefs — vital to fisheries and tourism — are facing the most prolonged and widespread bleaching event in recorded history, with over 80 per cent affected by marine heatwaves, a global reef preservation initiative said on April 23.

In April 2024, the US' National Oceanic and Atmospheric Administration (NOAA) and the International Coral Reef Initiative (ICRI) declared the world's fourth global coral bleaching event — the second in a decade.

One year on, the bleaching event continues to spread, driven by abnormally warm sea surface temperatures.

Bleaching refers to the whitening of corals when they expel the photosynthetic algae that give them their colour and provide them with essential nutrients.

All it takes is for water temperatures to rise 1 deg C to 2 deg C above average for corals to bleach.

From Jan 1, 2023, to March 30, 2025, bleaching-level heat stress impacted 84 per cent of the world's reefs, with 82 countries, territories and economies suffering damage, ICRI said in a statement.

The initiative comprises 102 members, including dozens of countries, UN agencies, conservation groups and companies, and is focused on research and better reef management.

"2023-2024 saw the highest ocean temperatures ever recorded — a surge that shattered previous records," said Associate Professor Alex Sen Gupta from the Centre for Marine Science and Innovation at the University of New South Wales in Sydney.