Context: In January 2025, a marine heatwave (MHW) off Western Australia’s coast led to the death of over 30,000 fish. Climate change has made such events up to 100 times more likely. These MHWs, which began in September 2024, continue to intensify, with sea surface temperatures (SST) rising by 2°C or more above average in some areas. This ranks as the second-worst MHW in the region’s history, following the extreme 2010–11 event.
What are Marine Heatwaves?
Marine heatwaves occur when sea surface temperatures rise 3–4°C above average for at least five consecutive days, lasting weeks, months, or even years. Over recent decades, MHWs have become longer, more frequent, and more intense. Studies show:
- Since 1982: MHW days have doubled.
- Past decade: A 50% increase in MHWs, as per a 2021 IUCN report.
Why has MHWs Intensified?
The primary driver is climate change, with oceans absorbing 90% of excess heat. Since 1850, global SSTs have risen nearly 0.9°C, with rapid acceleration in the last four decades. Projections indicate that MHWs will escalate dramatically with further global warming.
Impact of Marine Heatwaves
MHWs severely disrupt marine ecosystems:
- Fish Kills & Habitat Destruction: The 2010–11 MHW caused mass fish deaths and wiped out kelp forests.
- Coral Bleaching: Weakens reefs, endangering marine life. The Great Barrier Reef suffered its seventh mass bleaching event in 2024.
Way Forward
As climate change worsens, MHWs are expected to intensify, posing a major threat to marine conservation. Urgent global action is needed to mitigate climate change and protect ocean ecosystems. If warming trends continue unchecked, MHWs will become a permanent and destructive feature of the planet’s oceans, necessitating immediate international cooperation to combat their impact.
