Cairns, Australia – On Tuesday, top scientists warned that Australia's Great Barrier Reef (GBR) is at a very high risk of extreme and widespread coral bleaching and complete "ecosystem collapse" due to this year's El Nino event.
Often dubbed the world's largest living structure, the GBR stretches nearly 1430 miles along the coast of Australia and is a major tourism draw.
It was nearly listed as endangered earlier this month, the United Nations expressing "utmost concern" about mass coral bleaching and the impacts of climate change.
Morgan Pratchett, a marine conservation ecologist at Queensland's James Cook University, told the International Coral Reef Symposium in New Zealand that "extreme El Nino" posed a significant concern.
"It's not outside of the realm of possibility that the next major disturbance will lead to localized species extinctions… and widespread ecosystem collapse," Pratchett said.
This year's El Nino is expected to break records for its overall strength as it warms surface temperatures in the central and eastern equatorial Pacific Ocean, bringing worldwide changes in winds, pressure, and rainfall patterns.
"It's a very high likelihood that we'll see very high severity and large-scale mass bleaching on the Great Barrier Reef," Pratchett said.
Scientists sound the alarm, declare the reef "in danger"
UNESCO has been monitoring the reef annually since 2021.
Hard coral cover across the reef declined substantially in 2024–2025, with above-average water temperatures causing the reef's sixth mass coral bleaching event since 2016.
Extreme weather, land-based run-off, coastal development, and predation by the Crown of Thorns starfish also put the reef under pressure.
Marine studies professor Ove Hoegh-Guldberg from the University of Queensland said a lack of government action had globally threatened the future of coral reefs around the world.
"This could be the precursor to the loss of humans," he said.
"If you were on a big boat, like the Titanic, and someone comes up to you and says the boat's going down, you bloody well get on those lifeboats and start acting and do stuff," Hoegh-Guldberg said.
"We're not doing that. The ship is starting to sink in a really massive way, and we're not seeing it as what it is. It is so serious," Hoegh-Guldberg said.