The Great Barrier Reef is considered by many as Australia’s most incredible natural wonder – but it’s also our most vulnerable. Rising ocean temperatures and mass bleaching have drastically reduced coral cover, and emerging research shows this collapse might be rewiring the brains and personalities of the reef’s fish.
In 2024, the Great Barrier Reef suffered its fifth mass coral bleaching event in just eight years. According to the Australian Institute of Marine Science’s annual report, more than 30 per cent of corals were bleached across the reef – the largest area ever recorded – with cyclones and crown-of-thorns starfish outbreaks only making matters worse.
Climate change isn’t just shrinking our once-vibrant coral reefs; it's reducing their complexity, and as a result, could be rewiring the brains of the fish that live there. While little research has explored how climate change affects fish intelligence, Macquarie University ecologist Annabell Klinke is investigating the question from One Tree Island, a protected, tourism-free coral cay in the southern Great Barrier Reef.
Klinke explains, “We know, from both lab-based and wild studies, that animals living in more complex environments often develop more advanced intelligence. For example, fish that live in complex habitats, like healthy coral reefs, tend to have larger brains and stronger problem-solving skills than those in simpler ones.”
As corals die and reefs lose their structure, they become flat and simple, a process known as reef flattening. This could reduce opportunities for fish to develop or use their cognitive abilities. For example, a fish that struggles to learn or remember might not find enough food or may fail to spot danger in time. If they can’t adapt to changes in their environment, they might choose poor breeding sites or be less successful at raising their offspring. Over time, these small challenges add up. Fewer fish survive, populations shrink and the delicate balance of the reef begins to shift.”
This problem isn’t unique to the Great Barrier Reef. A 2018 report from the Intergovernmental Panel on Climate Change (IPCC) projects that all coral reefs could vanish within our lifetime – possibly by 2050 or even sooner – unless urgent, coordinated action is taken to protect them and the incredible diversity of life they sustain.
“Luckily, there’s still hope,” says Klinke. “Fish brains are incredibly adaptable; they can change and rewire throughout a fish’s life. That means if we protect and restore their habitats, fish have the potential to recover, learn and thrive.”
Saving our coral reefs isn’t just for scientists – small steps like composting, using public transport or eating less meat can make a difference. As Klinke says, “All these small actions can have a ripple effect – just like waves – to protect the reefs, the fish and the extraordinary intelligence.”