As Western Australia swelters through another record-breaking summer, the UNESCO-protected Ningaloo Reef off Western Australia’s coast is bleaching under the extreme and prolonged marine heatwave. Scientists warn that if the heat stress persists, large-scale coral death could follow.
National Oceanic and Atmospheric Administration (NOAA) data shows that the Ningaloo Reef has now reached over 15°C in degree heating weeks (DHW), which is a measure of reef heat stress over time. Significant coral bleaching is likely above 4 DHW, with coral death expected at above 8 DHW. For the time of year, the heat stress on Ningaloo is even higher than in 2011, the worst bleaching event ever on the 260 km long reef.
In 2024, Australia’s other great reef – the Great Barrier Reef – faced record heat stress during a global coral bleaching event. The event recorded 14.5 DHW, less than Ningaloo is suffering now.
Marine Heatwave in Western Australia
Previous analysis from Climate Central found that the marine heatwave that has persisted along the Western Australian coastline since September 2023, was made between 20 and 100 times more likely by climate change. “This prolonged marine heatwave off Western Australia is a clear sign of a warming climate, with extreme ocean temperatures causing severe ecosystem impacts. It highlights the profound effect of human-caused warming on our oceans,” said Dr. Andrew Pershing, chief program officer at Climate Central.
Two Years of Extreme Heat Pushes Ecosystems to the Brink
Another study published in Nature Climate Change found that globally, marine heatwave days were nearly three and a half times higher in the summers of 2023 and 2024 than in any previous year on record.
The consequences for Australasia have been severe, with extensive coral bleaching across Australia and the Pacific Islands, flooding and landslides and stronger tropical cyclones. Cyclone Gabrielle in New Zealand caused USD 8 billion in damages, with climate change increasing rainfall intensity. Marine heatwaves also forced the temporary closure of oyster farms in Australia and increased whale and dolphin strandings in New Zealand. Off Tasmania, ocean heat stress was so extreme that NOAA ran out of colours for its temperature maps.
“Marine heatwaves have radically changed our marine ecosystems,” explained Associate Professor Alex Sen Gupta from the University of New South Wales. “This is evident in the permanent loss of kelp forests along hundreds of kilometres of the WA coastline and the severely degraded state of the Great Barrier Reef compared to just a few decades ago. Worsening marine heatwaves will continue to transform these and other ecosystems.”
“Climate change is responsible for the global increase in the frequency, duration, and intensity of marine heatwaves,” said Dr. Alistair Hobday, research director for the CSIRO’s Sustainable Marine Futures Program. “The largest events we have seen in Western Australia and around the world have all been attributed to climate change.”
Coral Reefs Face Extinction Due to Climate Change
The ocean plays a vital role in regulating the climate, supporting marine life and sustaining billions of people through food and livelihoods. Ningaloo Reef and its surrounding coastline contribute almost USD 70 million annually to the local economy and support over 1,000 jobs. However, as marine heatwaves worsen with climate change, these functions are at risk.
Hotter ocean temperatures cause corals to first bleach as they expel the algae that give them their colour. If temperatures do not fall quickly enough, they then die. If climate change continues on it’s current path, marine heatwaves could be 20 to 50 times more frequent and 10 times more intense by the end of the century, and coral reefs are likely to go extinct globally. Even with 1.5°C global warming – a level we are likely to reach in around five years’ time – these highly diverse ecosystems could decline by 70-90%.
With fossil fuel burning the main driver of catastrophic climate change, replacing oil, coal and gas with renewable energy is critical to safeguard ocean life and coastal communities. Yet global carbon emissions from fossil fuels reached a new record high in 2024, with no evidence that the world has yet achieved peak emissions. “Only by reaching net zero emissions can we eventually halt this temperature increase and prevent worsening marine heatwaves,” said Gupta. “And we are a long way from achieving that.”
Supporting Coastal Communities
The world must act swiftly to protect marine ecosystems, both with rapid decarbonisation measures to prevent worsening marine heatwaves, and with widespread adaptation and support for coastal communities already impacted. Rose-Liza Eisma-Osorio, acting vice president at Oceana Philippines, said: “As a nation dependent on healthy and productive ocean, especially for poor artisanal fisherfolk and their families in coastal communities for food and livelihood, it is vital that stronger protection measures are in place. As warmer seas lead to widespread coral bleaching, threatening marine habitat and sustainable fisheries, national and local governments should be held accountable for the safety and survival of the people.”
Evelyn Smail
Writer, United Kingdom
Evelyn is a freelance writer and journalist specialising in climate science and policy, the just energy transition and the human impacts of climate change. She writes for independent publications, NGOs and environmental organisations. Evelyn has a background in sustainable development, climate justice and human rights.
Evelyn is a freelance writer and journalist specialising in climate science and policy, the just energy transition and the human impacts of climate change. She writes for independent publications, NGOs and environmental organisations. Evelyn has a background in sustainable development, climate justice and human rights.
