A near doubling of hard coral cover in the southern Great Barrier Reef over three years shows the ecosystem can recover from severe weather provided efforts are made to support its natural resilience, according to the Great Barrier Reef Marine Park Authority.
New Australian Institute of Marine Science data — that pre-dates the current mass coral bleaching — shows coral cover in the Reef’s southern sector (between Bowen and the Marine Park’s southern boundary) rose by 90 per cent between 2012 and 2015.
Coral cover in the central sector (between Cooktown and Bowen) rose by 22.9 per cent while a cyclone and predation by the coral-eating crown-of-thorns starfish led to a decline in the northern sector (north of Cooktown) by 19.7 per cent.
Overall, coral cover across the Reef rose by 19.3 per cent between 2012 and 2015.
Great Barrier Reef Marine Park Authority Chairman Dr Russell Reichelt said the new figures provided insights into coral health.
“The increase in southern and central coral cover over a relatively calm period since 2008 to 2011, when there were severe floods and cyclones, suggests the ecosystem is resilient and retains the capacity to bounce back when it’s not subject to repeated severe disturbances,” Dr Reichelt said.
“While this respite is welcome, we’re aware that warming trends in sea temperatures have been predicted to continue under future climate predictions. When periodic, strong El Nino conditions combine with the underlying warming trends, the risk of summer bleaching events increases from year to year.
“This is why current efforts to boost the Reef’s resilience by improving water quality and reducing the frequency and severity of crown-of-thorns starfish outbreaks are critical — the greater the resilience, the greater chance the Reef will have to regenerate quickly after disturbances.”
In the southern and central sectors, fast-growing branching corals account for much of the coral cover increase. Recovery by many other coral types will take longer because of different growth rates, ranging from years to decades.
Dr Reichelt said while he welcomed the improvement in the southern and central sectors of the Marine Park, the current mass bleaching would inevitably affect coral condition, particularly in the far north which historically had the greatest coral abundance.
“I expect future long-term monitoring reports will show further declines in the far north because of bleaching-induced mortality, and the impact of cyclone Nathan which occurred after these surveys were done,” he said.
“The situation strongly reinforces the importance of protecting the remote far northern sector from further pressures wherever possible — and that includes ensuring water quality in this part of the Marine Park remains high, so as to foster coral growth.”
The Australian and Queensland government’s Reef 2050 Plan is working to boost the health and resilience of the Reef by improving water quality through the reduction of land-sourced pollution, tackling the crown-of-thorns starfish, and restoring coastal ecosystems.
Regular updates about coral bleaching on the Great Barrier Reef can be found at www.gbrmpa.gov.au.