Great Barrier Reef threatened by hottest ocean temperatures in 400 years

Australia’s Great Barrier Reef, which is the world's largest reef, has come under threat as a result of water temperatures in and around the reef rising to their warmest in 400 years over the past decade.

This revelation was made by researchers in a study published on Thursday which puts the effects of man-made climate change into historical context, Reuters reported.

The reef, the world's largest living ecosystem, stretches for some 2,400 kilometres off the coast of the northern state of Queensland.

A group of scientists at universities across Australia drilled cores into the coral and analysed the samples to measure summer ocean temperatures going back to 1618.

Combined with ship and satellite data going back around a hundred years, the results show ocean temperatures that were stable for hundreds of years begin to rise from 1900 onwards as a result of human influence, the research concluded.

From 1960 to 2024, the study's authors observed an average annual warming for January to March of 0.12°C per decade.

Since 2016, the reef has experienced five summers of mass coral bleaching, when large sections of the reef turn white due to heat stress, putting them at greater risk of death.

These summers were during five of the six warmest years in the last four centuries, the study showed.

"The world is losing one of its icons," said Benjamin Henley, an academic at the University of Melbourne and one of the study's co-authors.

"I find that to be an absolute tragedy. It's hard to understand how that can happen on our watch in our lifetime. So it's very, very sad."

The last temperature data point, from January to March of this year, was the highest on record and "head and shoulders" above any other year, Henley said.

Coral reefs protect shorelines from erosion, are home to thousands of species of fish, and are an important source of tourism revenue in many countries.

At least 54 countries and regions have experienced mass bleaching of their reefs since February 2023 as climate change warms the ocean's surface waters, the United States National Oceanic and Atmospheric Administration (NOAA) has said.