Reef fate bleak, not fatal, under coral-centric models

Famous corals in the Great Barrier Reef face a bleak future under the current course of global warming, but may have time to adapt if temperatures don’t rise above 2C, according to new modelling.

The University of Queensland’s “coral-centric” analysis builds on existing modeling that focuses on ocean temperatures high enough to trigger mass bleaching events.

In reality, UQ professor Peter Mumby and co-author of the study said warm-water coral ecosystems were more complex and adaptable.

“Essentially, what we’ve used to guide our prediction of what the fate of the reef will say in the future has sort of ignored the coral biology within the coral ecosystem,” he told AAP.

Some coral species and reef areas are more resilient to heat than others and can help nearby reefs recover before the next bleaching event occurs.

Reefs near strong currents do best because they are exposed to blasts of cold water from the depths.

Ecosystems that are well-connected to coral populations that can provide new babies also tend to be healthier.

Advanced simulations have allowed Australian researchers to make discoveries that previous studies had missed.

The findings at 2°C, the upper limit of the Paris climate agreement, differ from existing research that assumes tropical reefs would effectively disappear if temperatures rose that much.

Prof Mumby said reefs would deteriorate when evolutionary adaptation was taken into account, but “highly dynamic” populations would remain at 2C.

“This certainly won’t be the end of corals, and these systems will respond very positively to reef management.”

But with warming approaching 3°C, corals will be “heavily degraded”, especially from mid-century onwards.

While Paris signatories are still following the temperature limits set out in the agreement, temperatures can be expected to rise by 2.7 degrees in current policy environments.

Prof Mumby said the findings had several implications for policymakers.

The first of these was the reduction of greenhouse gas emissions.

Countries including Australia are in a position to reaffirm their commitment to limiting warming to 2°C at next week’s COP30 climate talks in Brazil.

Second, localized reef management was important in all warming scenarios.

This includes managing numbers of coral-eating spiny starfish and stricter enforcement of marine park restrictions.

Deforestation in watersheds that flow into the Great Barrier Reef also harms corals by causing soil erosion and worsening water quality.