Australia’s Great Barrier Reef has suffered its steepest coral decline in nearly four decades, according to a new government report. A record-breaking marine heatwave in 2024, intensified by El Niño conditions, triggered widespread coral bleaching across the reef’s 2,300-kilometer expanse. The Australian Institute of Marine Science found that between a quarter and a third of hard coral cover was lost across its three main regions, with some reefs losing up to 70% of living coral. The bleaching event was the most spatially extensive ever recorded, with the northern and southern sections experiencing the largest annual declines since monitoring began in 1986. Scientists warn the reef may be approaching a tipping point, raising urgent concerns about its ability to recover amid escalating climate pressures.
CNN documented the widespread bleaching during visits to Australia’s Great Barrier Reef in 2024 and the Ningaloo Reef on the western coast in 2025. One scientist, surveying the damage, described it as “wildfires underwater”—a stark metaphor capturing the scale and urgency of the crisis unfolding beneath the surface.
The transformation of a vibrant coral reef into a ghostly white expanse is one of the most alarming signs of a warming planet. Coral bleaching doesn’t just erase color from the ocean—it threatens marine ecosystems and human livelihoods.
Click to learn what coral bleaching is, what causes it, and what can still be done to prevent it.