Coral cover on two-thirds of Australia’s Great Barrier Reef has reached its highest level since records began 36 years ago, according to marine scientists monitoring the ecosystem. marine ecosystem monitoring.
But corals remain highly vulnerable to mass bleaching events, which are becoming increasingly frequent as human activity warms the oceans, the Australian Institute of Marine Science (AIMS) said in its annual report. his year.
Restoration in the central and northern bands of the UNESCO World Heritage-listed reef did not extend to the southern region, which lost coral cover amid outbreaks of thorny starfish. .
The Great Barrier Reef remains an “elastic system” that “remains resilient to disturbances”, said AIMS monitoring program chief Mike Emslie.
“But what is worrying is that the frequency of these disturbance events is increasing, especially those of mass coral bleaching,” he added.
Earlier this year saw the first mass bleaching of the La Niña year, a natural climate cycle that typically brings cooler temperatures that allow corals to recover. This is the fourth mass bleaching event in seven years.
Dr Emslie said climate change is driving sea heat waves to become more frequent and longer lasting.
“The increasing frequency of warming ocean temperatures and the magnitude of mass bleaching events demonstrate the dire threat that climate change poses to all coral reefs,” he said. especially while thorny starfish outbreaks and tropical cyclones are also occurring.”
“Future disturbances could reverse the observed recovery in a short period of time,” he warned.
AIMS CEO Dr Paul Hardisty said the increasing frequency of such events was “uncharted territory” for the reef.
“In our 36 years of monitoring the condition of the Great Barrier Reef, we have not seen bleaching events so close together,” he said.
The report comes as UNESCO considers whether to list the Great Barrier Reef as “in danger”, following a visit by the UN agency in March.
The issue was scheduled to be discussed at a World Heritage Committee meeting in Russia in June, but was later postponed.
In an important measure of reef health, the AIMS defines the coverage of hard corals more than 30% as a high value, based on its long duration.
survey of coral reefs.
In the Northern region, the average hard coral cover increases to 36% by 2022, while in the Central region the hard coral cover increases to 33% – the highest recorded for both regions. since the institute began monitoring the reef in 1985.
But in the southern region, which typically has higher hard coral cover than the other two, cover has fallen to 34% by 2022 from 38% a year earlier.
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