The Great Barrier Reef is showing new signs of recovery after two years marked by heat-related bleaching events.
The Australian Institute of Marine Science’s annual survey covers 121 reefs examined using a method called “manta tow”. An observer is slowly towed behind a boat and estimates the proportion of the seabed covered by living hard corals. This cover serves as a simple indicator for tracking how reefs change over the years.
Image Wikimedia
This time, 56% of the surveyed reefs experienced no clear change in coral cover. An increase was even recorded on 28% of them. Across the Great Barrier Reef’s three major regions, the situation therefore appears more stable than a year earlier, when losses had been particularly severe.
To understand this reversal, we need to look at the weather during the 2025–2026 southern summer. Marine heat persisted and caused regional bleaching in the north. However, rain, clouds, and several weather systems limited heat buildup in some areas. The corals there experienced less severe thermal stress than during previous events.
Bleaching occurs when water remains too warm. The corals then expel the tiny algae living in their tissues, which provide them with much of their energy. They become pale or white, but do not necessarily die. If conditions become favorable again quickly enough, some may recover.
The situation remains very different from one area to another. Hard-coral cover increased in the northern and central regions. In the south, the change was small and remained within the margin of measurement uncertainty. These results therefore do not mean that every reef is recovering, or that all types of coral respond in the same way.
This distinction is especially important after the previous shock. The 2024–2025 report measured regional declines ranging from approximately 14% to 31% compared with the previous year. Corals of the genus Acropora, which grow quickly and had contributed substantially to previous increases in coral cover, were also heavily affected by the heat.
Other pressures continue at the same time. Cyclones and freshwater inflows can damage some reefs. Crown-of-thorns starfish also feed on corals, with a new outbreak observed in the north. These disturbances can affect the same area one after another and reduce the time available for its recovery.
The next survey will notably need to determine whether the observed gains withstand the new hot summers. The AIMS program has monitored the Great Barrier Reef for 40 years, making it possible to distinguish a temporary improvement from a lasting trend. With bleaching events now occurring closer together, the amount of time between two disturbances is becoming particularly important.