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Record-breaking coral bleaching lays waste to WA’s most prized reefs
By Emma Young
Last summer’s marine heatwave off Western Australia was the longest, largest and most intense on record for the state, resulting in its most widespread coral bleaching event ever.
While the full impact is still unfolding, experts from numerous organisations and agencies forming the WA Coral Bleaching Group have on Tuesday reported bleaching and mortality ranging from medium (11-30 per cent) to extreme (90 per cent) levels across systems up to 1500 kilometres apart.
Bleaching at Ningaloo’s Tantabiddi Reef. Credit: Declan Stick / AIMS
The summary says researchers found 31-60 per cent bleaching and mortality at Ningaloo Reef monitoring sites, and 61-90 per cent mortality at Mermaid and Clerke Reefs, Rowley Shoals.
At inshore southern Kimberley reefs, they recorded 31-60 per cent bleaching with mortality in March; at Ashmore Reef, they recorded 11-30 per cent bleaching and mortality with one site at 31-60 per cent.
Members of the bleaching group, convened by the Australian Institute of Marine Science, began monitoring the heatwave in September. Heat stress peaked in December, January and again in March/April.
Areas that had rarely or never bleached before, like Rowley Shoals, north Kimberley and Ningaloo, had been hit hard, AIMS senior research scientist Dr James Gilmour said.
“The length and intensity of the heat stress, and its footprint across multiple regions, is something we’ve never seen before on most of the reefs in WA,” he said.
The stress is expected to beat records set during the 2011 La Nina and the 2016 El Nino on all but the southernmost reefs.
The full impact is still being assessed, and some bleached coral may recover, but it can take a reef 10-15 years to recover fully.
Australian sea surface temperatures last summer were the warmest since official records began, the Bureau of Meteorology’s Dr Claire Spillman said.
Gilmour said this event occurred alongside mass bleaching on the Great Barrier Reef and continued the ongoing fourth Global Coral Bleaching Event that began in 2023 and had circumnavigated our oceans in a wave of coral mortality.
Bleaching at Rowley Shoals. Credit: Anna Cresswell/AIMS
He said these events, were becoming more frequent, more intense and more widespread, giving reefs little time to recover.
The report states that climate change caused by carbon emissions remains the greatest threat to all reefs globally.
WA Greens spokesperson for Healthy Oceans and Climate Change, Sophie McNeill, said what she witnessed at Ningaloo was heartbreaking.
“Swathes of our stunning World Heritage Listed reef now look like a coral graveyard,” she said.
“These images of our dead and dying coral coast are deeply distressing for every West Australian who loves our oceans.
“I also saw firsthand the shock and grief so many members of the Exmouth community are now experiencing.
“We have a Labor government that is continuing to ignore the science and push for fossil fuel expansion.
“Now is the time for Labor to pick whose side they are on – that of WA communities like Exmouth and all the wonderful people who work on our stunning reef? Or that of Woodside which is actively destroying Ningaloo before our eyes?”
McNeill said WA was the only state with rising emissions and no 2030 reduction target and this was threatening national targets.
Bleaching at Rowley Shoals. Credit: Anna Cresswell/AIMS
“How much more of our beautiful reef has to die on [WA Labor’s] watch before they finally stop working for Woodside and start working to protect our planet and our kids’ future?” she said.
“This week the Greens will be debating our Climate Bill in the WA parliament, and we are calling on WA Labor to support the legislation and end their climate denial.”
Conservation Council of WA executive director Matt Roberts said the report highlighted the “threat” from Woodside’s proposed Browse Basin gas project, which would unlock 1.6 billion tonnes of greenhouse gases, equivalent to nearly 20 times WA’s annual emissions, and nearly 3.5 times Australia’s total annual emissions.
He said with still only 25 per cent of WA’s energy being produced by renewables, and the government must set a renewable energy target and give investors the confidence to develop projects in WA, as they were elsewhere.
“No matter how the state government spins gas as a transitional energy source, this isn’t a science-based solution towards net zero; it’s the ultimate exercise in climate gaslighting,” he said.
Environment Minister Matthew Swinbourne met researchers Tuesday morning and visited the region in the past fortnight. He told reporters on Tuesday the government was “deeply concerned” and “monitoring the progress of the damage”.
Swinbourn said WA remained “committed to dealing with our carbon emissions” but said major players including the US walking back commitments made WA’s actions “pale into insignificance” and rendered reductions in WA “meaningless”.
“What will address this is global action on climate change,” he said.
He said Minister for Energy and Decarbonisation Amber Sanderson was working on new legislation regarding a 2050 net zero target.
Asked about 2030 targets, proposed Tuesday by Climate Analytics, he said WA needed “to be careful in terms of what we set and what we can achieve” but again this was a matter for Minister Sanderson.
“It’s all very well to send a virtue-signalling type of target,” he said.
“But these things don’t happen in a vacuum, they affect other areas of our economy … it’s a competitive space out there.”
He said WA was ending coal use and modernising its transmission network for renewables.
He further told this masthead that since WA’s climate legislation was introduced, the way greenhouse gas emissions from industry in WA were regulated had changed, with the federal government taking the lead through the strengthened safeguard mechanism.
“Considering this changed regulatory environment, the state government is taking some time to review the legislation,” he said.
“We are focused on ensuring that our approach aligns with the most effective measures available to drive down emissions and support our transition to a decarbonised economy.”
Woodside was contacted for comment.
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