Underwater worlds on the brink of rapid change as water heats
The IUCN Red List has been updated, and close to half of warm-water corals are now threatened with extinction.
If you dip your head beneath the surface of the water and swim into a tropical reef, you’ll enter one of the Earth’s most biodiverse ecosystems. But close to half the corals that make up these underwater worlds are being heated by climate change to the point of collapse.
A new assessment by the International Union for Conservation of Nature (IUCN) has concluded 44 per cent of the world’s 892 warm-water, reef-building coral species are threatened with extinction. This was the first major assessment of these organisms for its Red List of endangered species since 2008, and at that time only a third were in trouble.
The warning comes as world leaders meet at COP29 to discuss how to slow global warming. Experts say they are almost certain this year will be the hottest on record.
Climate change single greatest threat to world's reefs
According to the European Union’s Copernicus Climate Change Service, 2024 will also be the first year global temperatures have warmed by 1.5 degrees above the pre-industrial average. The overarching goal of the 2015 COP21 in Paris had been to “limit the temperature increase to 1.5 degrees”, something it appears our leaders will fail to do.
The IUCN’s Director General, Dr Grethel Aguilar, said the state of warm-water coral “drives home the severity of the consequences” of our rapidly changing planet.
Coral reefs are essential for breaking down the severity of storms before they make land, creating habitat for fish that feed millions of people, stabilising coastlines, and storing carbon.
“The protection of our biodiversity is not only vital for our well-being but crucial for our survival. Climate change remains the leading threat to reef-building corals and is devastating the natural systems we depend on,” Aguilar said.
“We must take bold, decisive action to cut greenhouse gas emissions if we are to secure a sustainable future for humanity.”
Australia's world-famous reef hit by succession of bleaching events
Australia’s Great Barrier Reef was first extensively bleached in 1998, then again in 2002, 2016, 2017, 2020 and 2022. The latest event occurred in 2024, bleaching around three quarters of the reef.
This bleaching effect occurs when coral is stressed by warming waters, causing it to expel the algae that gives it colour and helps provide it with energy. While this process doesn’t immediately kill the coral, it weakens it and with bleaching events becoming a regular occurrence, corals aren’t having time to recover before they’re impacted again.
The Great Barrier Reef is listed by UNESCO as a World Heritage area, and because of its decline there have been efforts by experts to have it listed as “in danger”. But the Morrison and Albanese governments have successfully campaigned against the listing, and to date they have been successful.
Cool water reefs face series of alternate threats
Coral reefs are built over tens of thousands of years, and so recovery from bleaching and extreme weather events is slow.
While the research focused on warm-water corals, an assessment of their cold-water cousins is imminent. They are found in deep cold waters like the Lord Howe Rise off Australia’s coast. Earlier this month it was revealed a New Zealand fishing vessel had accidentally hauled up close to 40kg of this coral from the ocean floor.
Greenpeace labelled the act, which is under investigation, as an act of “environmental vandalism”.
While cold water species face less of a threat from climate change, its destruction is primarily coming from fishing trawlers, along with deep sea mining, drilling for oil and gas, and laying of deep-sea cables.
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