The arrival of El Niño has been triggering alerts around the world. Scientists warned on Tuesday (21) that the excessive heat brought by the phenomenon places Australia's Great Barrier Reef at very high risk of suffering extreme and widespread bleaching, which could lead to an ecosystem collapse.
Marine ecologist Morgan Pratchett from James Cook University in Queensland, specializing in marine conservation, stated that an "extreme" El Niño represents a significant concern.
"It is not impossible that the next major [climate] disturbance will cause localized species extinctions," he declared at the International Coral Reef Symposium held in Auckland, New Zealand.
Considered the largest living structure in the world, this coral formation extends 2,300 kilometers along the northeastern coast of the Australian state of Queensland and is one of its main tourist attractions.
This year's El Niño phenomenon is expected to be one of the strongest ever recorded. The phenomenon is characterized by rising surface temperatures in the central and eastern equatorial Pacific, which causes changes in global wind, pressure, and rainfall patterns.
"It is very likely that we will see large-scale, high-severity mass bleaching on the Great Barrier Reef," said Pratchett.
UNESCO has been monitoring the reef annually since 2021, when it warned that it was at risk of being added to the list of "in danger" world heritage sites.
This month, the Australian government maneuvered to prevent the region from receiving that classification, despite the United Nations having expressed its "utmost concern" over the recurrence of mass bleaching events, caused by elevated ocean warming, and the impact of climate change.
Hard coral cover across the reef declined substantially between 2024 and 2025, following the most recent mass bleaching event at the site — the sixth since 2016. Bleaching is not necessarily fatal to corals, but it leaves them weakened, and when prolonged and repeated, can lead to the death of entire colonies.
Ove Hoegh-Guldberg, professor of marine studies at the University of Queensland, stated that the lack of government action jeopardizes the future of coral reefs worldwide. "This could be the prelude to the disappearance of humanity," he said.
"If you were on a great ship, like the Titanic, and someone came up to you and said the ship is sinking, you would undoubtedly climb into one of those lifeboats and start acting and doing something, but we are not doing that," he warned. "The ship is starting to sink in a truly massive way, and we are not seeing reality. It is very serious."
