Image: © Andrea Izzotti/Stock.adobe.com
Despite significant losses in some parts of the Reef, coral cover in the Queensland region remains at a moderate level.
The Australian Institute of Marine Science (AIMS), in a survey of the coral cover between Lizard Island and Cardwell, a coastal town in Queensland, found “substantial losses” in 12 of the 19 reefs surveyed.
The AIMS’ Long Term Monitoring Program (LTMP) monitors coral reef condition for up to 130 reefs annually along the Great Barrier Reef.
In its first routine survey of the area following a summer of “disturbances” – when the area experienced a mass bleaching event, two cyclones and flooding – the institute found coral cover loss ranging from 11-72pc of pre-summer levels on 12 reefs.
More than a third of the area’s hard coral cover, which is a measure of the percentage of live coral on the reef surface, was lost across the Cooktown Lizard Island sector – the largest annual decline for this sector in 39 years of AIMS’ monitoring, the institute said in a statement yesterday (19 November).
Higher than average sea surface temperature is the biggest stressor to coral reefs, and 2024, unfortunately, is on track to become the warmest year on record.
“During February and March 2024, all the reefs we recently surveyed in this north Queensland region were subjected to levels of climate change-driven heat stress that cause bleaching,” said AIMS’ LTMP leader Dr Mike Emslie. “The heat stress got so high in some areas that mortality is not a surprising outcome.
“Tropical Cyclones Jasper and Kirrily also exposed many to wave heights likely to cause damage to corals.
“From what we have seen so far, the impact from these events is significant coral mortality in those areas hardest hit,” he said, “although … a few reefs escaped significant loss.”
The survey found that while the inner and mid-shelf reefs in the Cooktown-Lizard Island sector took the biggest hit from coral bleaching – with one inner shelf reef losing almost 75pc of its pre-summer hard coral cover – the outer shelf reefs that the institute surveyed escaped with little to no coral loss.
Still, AIMS reiterated that the losses are significant.
“The losses of coral we’ve recorded so far are significant,” said AIMS acting research program director Dr Manuel Gonzalez Rivero.
However, according to Rivero, despite these losses, coral cover on most reefs in the Queensland region is at moderate levels of between 10 and 30pc.
“Climate change is threatening reefs around the world. Their future relies on strong greenhouse gas emissions reduction, management of local and regional pressures, and the development of approaches to help reefs adapt to and recover from its impacts, which we are already seeing,” Rivero said.
A 2018 study published in the journal Science, which analysed 100 tropical reef locations revealed that it might be too late to save coral reefs in their entirety.
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