The Great Barrier Reef has suffered its biggest loss of live coral in a single year in 40 years of monitoring, according to Australian scientists. This sharp decline comes mainly from coral bleaching caused by rising ocean temperatures linked to climate change. Despite this setback, the total amount of living coral remains close to the reef’s long-term average, thanks to steady gains since 2017.
The Great Barrier Reef, stretching 1,500 kilometers along Australia’s northeast coast and covering 344,000 square kilometers, is feeling the heat from more frequent and intense bleaching events. Mike Emslie, head of the reef monitoring program at the Australian Institute of Marine Science, shared that the live coral cover recorded in 2024 remains the highest in nearly four decades. Still, the drop experienced this year marks a record annual decline.
The reef is divided into three regions: north, central, and south. The southern section saw the hardest hit with coral cover shrinking by nearly one-third. The north dropped by about a quarter, and the central region saw a 14% reduction. These figures highlight the varied but widespread impact across the reef.
This coral loss is part of a larger global problem. The world is currently in the middle of the fourth-largest coral bleaching event ever recorded, which began in early 2023. Almost 84% of the world’s coral reefs have been affected by heat stress during this period, the U.S. National Oceanic and Atmospheric Administration reports. Australia alone surveyed nearly 300 reefs earlier this year and found bleaching on over 75 of them.
Coral bleaching happens when water stays too warm for too long, causing corals to expel the algae that live inside them and give them color. Bleached corals aren’t dead at first but become weaker and more prone to disease. Over time, repeated bleaching events can severely damage coral populations.
While reefs can recover after bleaching, each event leaves lasting scars, making it harder for corals to bounce back fully. Scientists warn that with global temperatures now 1.3 degrees Celsius higher than before industrial times, coral reefs face increasing threats. Research suggests that once the planet warms by about 1.2 degrees Celsius, coral ecosystems could disappear from many places.
This year’s report serves as a stark reminder that climate change is putting the Great Barrier Reef—and reefs around the world—under serious pressure. Without significant efforts to reduce global warming, the future of these vital ecosystems looks increasingly uncertain.