The Great Barrier Reef will continue to experience rapid coral decline through the middle of this century, but could still regain much of its health if global heating stays below 2°C, according to new modelling from the University of Queensland.
The findings challenge the widespread assumption that the reef has already moved past a point of irreversible collapse at 1.5°C of warming.
The research, published in the journal Nature Communications, uses the most detailed projections so far for the world’s largest coral system.
Unlike earlier studies that only modelled bleaching from heat stress, the UQ team also examined how corals evolve, how heat-tolerant traits can be passed down, how baby corals move between reefs, and how naturally cooler reef pockets can act as safe zones.
In total, the modelling covered all 3,800 individual reefs that make up the system.
The results showed that while the reef has an ability to adapt, this natural resilience is overwhelmed if warming continues at current rates.
According to the projections, coral cover is likely to drop sharply in the 2030s and 2040s as global temperatures rise towards 1.5°C.
Researchers found that by around 2040, the system could lose roughly half its coral. By 2050, only scattered regions would resemble what reefs look like today. However, if the world manages to keep heating under 2°C, coral populations could gradually recover later in the century, returning to levels that are close to those seen in recent decades.
The outlook becomes catastrophic if global emissions continue on the present trajectory.
The UN has warned that current national policies collectively lead the planet toward roughly 2.8°C of warming by 2100. Under that scenario, the modelling shows the Great Barrier Reef could be left with just around four per cent coral cover by the end of the century.
Professor Peter Mumby, one of the study’s lead authors, said this does not mean corals will disappear entirely, but it does point to a future of severe loss unless the world changes course.
Several reef scientists not involved in the study noted that relying on naturally cooler reefs for recovery may be too optimistic, given the pace at which marine heatwaves are intensifying. They said past warnings remain urgent: the only reliable way to safeguard the reef is to drastically reduce emissions.