Australia experiences the worst coral bleaching of the great barrier reef to date

In April 2024 the Government of Australia (in collaboration with the Australian Institute of Marne Science and the Reef Authority) released a highly impactful report describing the extent of Coral Bleaching in the Great Barrier Reef (GBR). Dr. Neal Cantin, Nicholas James and Dr. Jessica Stella asserted that the GBR has experienced a mass bleaching event (the 5th since 2016) resulting from thermal stress. The prolonged exposure of the reefs to high ocean temperatures has caused unprecedented damage. Whilst there is some capacity for the GBR to recover from this event, a large section has died resulting in irreversible effects. The U.S. National Oceanic and Atmospheric Administration (NOAA) has reported that since February of 2023, at least 53 countries and regions have experienced mass bleaching events. 

Coral bleaching occurs when heightened water temperatures cause corals to expel the colourful photosynthetic algae (known as zooxanthellae), living symbiotically within them. This expulsion results in the corals losing their colour, leaving them bone white (hence the term bleaching). Without their nutrient–absorbing algae, corals cannot survive. There is a clear link between the warming climate and instances of mass coral bleaching. As the surface areas of ocean waters increasingly warm, previously thriving reefs become totally inhospitable environments. Coral reefs are projected to decline by 70 to 90% at 1.5°C of global warming and by 99% at 2°C of global warming (above pre-industrial levels). 

During late 2023 and early 2024 a strong El Niño, in combination with human-caused climate change has driven global average sea surface temperatures to record highs for the past 10 months. As outlined in the Great Barrier Reef Authority’s Position Statement on Climate Change, climate change is the greatest threat to the Great Barrier Reef. ”All ecosystems within the Great Barrier Reef are vulnerable to the impacts of climate change. More extreme weather events such as heatwaves, tropical cyclones, and flood events, are accelerating the degradation of coral reefs, seagrass meadows and mangrove forests.”  

Do you want to know more about El Niño? Listen to expert Dr. Jennifer Francis here.     

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