Richard Musgrove
Australia’s sea-surface temperature anomalies are putting coral reefs at risk again.
National Oceanographic and Atmospheric Administration (NOAA) data shows the Great Barrier Reef off Cape York in Queensland, is again heading for a two-degree heat spike.
Coral bleaching expert, Professor Terry Hughes, said in a social media post on Bluesky 12 days ago: “Silence so far from the Australian government on the coral bleaching event on the northern Great Barrier Reef, repeating mass mortality there in 2016, 2017, 2020 and 2024.”
Hughes told Scientific American: We shouldn’t give up on the world’s coral reefs…but restoration is not the way to save them. The way to save them is to deal with greenhouse gas emissions…”
Meanwhile, Western Australia’s Ningaloo Reef is facing what could be its worst recorded bleaching event. With more to come through to May, 2025, according to NOAA predictions.
The late monsoon was the trigger. WA sea surface temperatures (SST) usually get hot around October November, but once the monsoon kicks in, things usually cool down, until March April, when they tend to rise again, says Dr James Gilmour of AIMS
But the monsoon just didn’t show up until a couple of weeks ago, when Cyclone Zelia came through, says Gilmour. This meant that December-January produced the hottest sea surface temperatures (SST) temperatures on record in the far north of WA, he says. “Really unprecedented, with temperatures 1-3 degrees above normal.”
That initially meant bleaching for reefs off the Kimberley, off Rowley Shoals 260km west of Broome and off the Pilbara.
Then the heat moved south, driven by weak La Nina conditions and the southerly -flowing Leeuwin current. Bleaching reached World-Heritage-listed Ningaloo Reef. Temperatures have been cooling, since then, with the monsoon, Gilmour says, but they’re expected to climb again in March April. “It’s not over yet for WA”.
Mass bleaching events also hit this coast in 1998, 2011-2013 and 2016, with many smaller bleaching events scattered throughout.
Do we have a coral future?
“There’s no doubt that we’re going to see the loss of biodiversity on reefs; in the number of corals on the reefs” says Gilmour. Some reefs or parts of reefs could completely lose corals, others, where cool water intrusions rise to the surface, might escape the worst of the heat stress, he adds.
There will always be corals that are tough enough to exist in low numbers, he says, but losing corals means shifting to macroalgae — an alternative community state. Such a change would mean a different set of goods and services, a different diversity of foods. “Perhaps we can nudge it in a direction that provides better goods and services for people and the environment” adds Gilmour.
Most importantly — we need a three-pronged approach, he says. Addressing carbon emissions is number one. Without such action, “everything’s going to cook, essentially, as we see on the land.”
” We also need a better understanding of adaptation rates and spatial variation, with traditional management approaches being key elements in reducing local pressures such as over-fishing and pollution.
“And the third, more extreme strategy — repopulating reefs with hardier heat-adapted species.”
An alternative community can still be a benefit to the environment and for humans, he says.
