SYDNEY, Feb. 11 (Xinhua) -- Coral bleaching from ocean warming is escalating in severity, extent and frequency, with more than half of the world's reefs affected during the 2014-17 global bleaching event, a study has warned.
Researchers from Australia's James Cook University (JCU) and partner institutions, including the U.S. National Oceanic Atmospheric Administration's Coral Reef Watch program, combined data from over 15,000 coral surveys with global satellite temperature data, said a JCU statement on Tuesday.
This approach allowed the scientists to better assess the true impact of the 2014-2017 Third Global Coral Bleaching Event and to predict the scale of damage expected during the current Fourth Event, it said.
The study, published in Nature Communications, found heat stress, bleaching and mortality during the 2014-2017 coral bleaching event were more severe than previously recorded, with more than half of the world's coral reefs suffering at least moderate bleaching and around one in six reefs losing over 10 percent of corals.
The central Pacific suffered the most severe bleaching and mortality, while severe heat in Fiji and the Great Barrier Reef caused some corals to rapidly die without bleaching first, the findings showed.
Coral bleaching results from the breakdown of the partnership between coral animals and their symbiotic algae due to stress, often due to unusually high summer temperatures. Under high levels of heat stress, corals can die, and the health of surviving corals remains impacted, researchers said.
"After the back-to-back bleaching events on the Great Barrier Reef in 2016 and 2017, coral cover began to rebound, only to be hit again by mass bleaching in 2020, 2024 and 2025," said JCU Professor and the study's co-lead author Scott Heron.
"This creates a downward ratchet effect, where reefs only partially recover before the next bleaching event impacts them even further," Heron said, adding that if greenhouse gas emissions will not be reduced in line with previous Paris climate agreement commitments, "we can expect to lose many of the ecosystem services coral reefs provide." ■
