Voracious wood-boring beetles continue to rapidly destroy the snow gum forests of the Australian Alps as climate change creates perfect conditions for them, reports JOHN KIDMAN.

Carrying some 14 trillion litres of water a year, the Murray River eventually empties into the Southern Ocean south of Adelaide via a vast network of estuaries and lagoons.

Two-and-a-half thousand kilometres away, trickling rivulets of melted snow are modest enough to be straddled by alpine hikers making their way to Australia’s highest peak.

Imagining a connection between the two seems almost as fanciful as the chaos theory quote about the butterfly that flaps its wings and causes a far-off catastrophe.

Yet it’s real.

The official source of the Murray, Indi Springs on the NSW-Victorian border, lies 40km south of Mount Kosciuszko.

Higher up, though, along with dozens more small creeks and streams, the otherwise unremarkable tributary is supplied by the slow release of seasonally frozen groundwater blanketed for months at a time with snow.

It’s thought more than a quarter of the Murray’s enormous flow originates this way despite the high country making up just one per cent of the river’s total catchment.

Now there’s mounting concern that the guardian of this extraordinary ecological contribution, the mountains’ iconic snow gum population, is under sustained siege.

Localised dieback of Eucalyptus pauciflora was first discovered within Kosciuszko National Park in the 1990s.

However, more widespread damage – along with the confirmed identity of the culprit, native wood-boring longicorn beetles – has only more recently come to notice, and there’s evidence climate change is exacerbating the problem.

The gums are now in steep decline across every subalpine habitat from Mt Buffalo in Victoria to Kosciuszko and the ACT’s Brindabella Range.

The infestation is relentless and, say experts, rapidly expanding.

Warmer winters and drier summers linked to climate change are allowing Phoracantha mastersi to thrive and spread.

The dieback is abundantly visible and a threat to Australia’s entire range of snow gum forest between 1600m and 1900m above sea level.

Typically, the trees are devoured top-to-bottom as beetle larvae penetrate their bark and feed on the ‘veins’ and ‘arteries’ they use to transport water and nutrients to and from the soil.

By the time tell-tale ringbarking scars reveal themselves, the gums are already dead or dying.

“It is not a minor issue that is playing out locally,” according to Australian National University’s Dr Matthew Brookhouse.

Few Australians realise that snow gums play an outsized role in capturing and feeding water into the Murray-Darling Basin, he says.

“If you diminish the capacity of these areas to yield water by taking away tree cover … you are losing significant amounts of water.

“The insects hit these trees again and again until they die,” he adds.

“At higher elevations these are the only trees that can survive the harsh conditions, so that puts everything that depends on them in danger as well.”

Think sphagnum moss, a veritable sponge able to absorb 20 times its own weight in moisture; sedge, known for its ability to filter and slow downslope water movement; and numerous alpine herbs and tussock grasses that promote infiltration.

Sans the gums, each of these mechanisms is stripped away and the terrain is left openly susceptible to indiscriminate run-off.

Less water directed into in the system could affect everything from food production to wildlife abundance in low-lying wetlands, Dr Brookhouse says.

Like the fictional butterfly effect, the flow-on is potentially calamitous.

Acting as the boundary between the nation’s two most populous states for roughly 2000km before forging through South Australia, the Murray provides water to about 1.5 million households.

Established regional centres including Albury-Wodonga, Echuca, Swan Hill, Mildura, Renmark and Murray Bridge all owe their livelihoods to the river to some degree.

Regulated by 35 dams, weirs and locks, the Murray-Darling Basin is managed by both federal and state governments, with numerous industries and smaller communities counted among its stakeholders.

Interconnected lakes and rivers included, the system covers a million square kilometres, or the equivalent of 14 per cent of Australia’s total land mass.

It accounts for more than a third of the nation’s food and fibre production.

The Murray also hosts myriad wildlife, with significant kangaroo, koala, wallaby, turtle and platypus populations tethered to its course and 46 native fish species found within its banks.

Upstream, as the air in Australia’s high country becomes warmer and drier, more moisture is drawn from the snow gums.

According to research led by ANU postdoctoral fellow Callum Bryant, these are the conditions in which the voracious longicorn beetle flourishes.

“Increased wood-borer damage was first observed around 2017 following the extreme El Nino event of 2015/2016,” say he and his colleagues.

“However, the present study, conducted in 2022, also noted 11 per cent of trees surveyed … demonstrated evidence of recent borer damage.”

While drier gums allow the insect proliferate, it’s hoped better hydrated surviving trees will stand a chance of resisting beetle populations into the future.

Yet it’s more likely frequent periods of drought and fire will put paid to any recovery the gums can muster themselves.

Using temperature-based models, Dr Brookhouse has determined Phoracantha mastersi may in fact be doubling down on its campaign.

“In the past, they typically emerged from their pupation chambers inside the wood of snow gums around late February,” he says.

“But in recent years that’s happened as early as December.

“That means they now have a much longer window to mate, lay eggs and attack trees.”

The challenge will be to find a landscape-scale solution among the beetle’s natural enemies.

Parasitoid wasps or other insects inclined to attack longicorn beetle eggs are a prime candidate.

Dr Brookhouse and his team are already working to identify and trap the right pest controllers but its a huge task and not yet happening in enough locations.

“It’s our best chance but we need to ramp up work across broad parts of Australia to find them,” he says.

“Achieving it will rely on ongoing partnerships across universities, parks and forest management agencies, as well as private industry and the community.”

NSW Parks and Wildlife Service is meanwhile monitoring the snow gum’s decline while awaiting the outcome of Dr Brookouse’s work and another project looking into the pheromone-based trapping of male beetles.

Significant strides have also been made with the volunteer planting of 2800 replacement snow gum seedlings across multiple subalpine sites.