Ocean temperatures in the Great Barrier Reef have hit their highest level in 400 years over the past decade, researchers say, warning that the largest living ecosystem on Earth likely will not survive if planetary warming is not stopped.

The study published on Thursday by a group of scientists from across Australia says temperatures around the spectacular 2,400km-long (1,500-mile) coral system were most stable for hundreds of years, but have warmed significantly in recent decades as a result of human influence.

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World’s coral reefs face global bleaching crisis

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Ocean temperatures around the reef increased yearly since 1960 but were particularly hotter during recent mass coral bleaching events, when large sections of the reef turned white due to heat stress, according to the study in the science journal Nature.

“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.”

Co-author Helen McGregor said she was “extremely concerned” about the reef, describing the temperature increases as “unprecedented”.

“These are corals that have lived for 400 years and this is the warmest temperatures they’re experiencing. These are the Redwood trees of the reef,” she told AFP news agency.

Since 2016, the world-famous reef has suffered from five rounds of massive coral bleaching due to warming temperatures, a lethal trend that is occurring at reefs across the world. These bleaching events happened during five of the six warmest years in the last four centuries, the study showed.

Scientists conducted the study by utilising ship and satellite data and by drilling into coral in order to analyse samples that help them understand changes in ocean temperature as far back as the year 1618.

Temperatures began to rise around the beginning of the 20th century and increased by an average of about 0.12 degrees Celsius (0.22 degrees Fahrenheit) for January to March from 1960 through 2024.

The reef is home to a wide variety of natural life, with 600 types of coral and 1,625 fish species alone. It is also a significant tourism boon for Australia, contributing about $4.2bn to the country’s economy each year.

The United Nations has recommended that the Great Barrier Reef be added to the list of at-risk world heritage sites, but Australia has refused those efforts over concerns that it could damage the reef’s tourism appeal.