Ghost forests: Australia’s snow gums under threat from climate change

From a distance, the white flush looks almost like a line of snow, freshly settled on the mountain slopes.

This is Mount Hotham, after all, one of Victoria’s most popular snowsports destinations, known best as a playground of powder snow and downhill ski runs, chair lifts and alpine lodges.

But the white haze that covers these slopes is not snow, it’s dead trees. Dead snow gums, to be precise, Eucalyptus pauciflora.

Cam Walker, from Friends of the Earth, at an area near Mount Hotham which has been burnt repeatedly in recent years. Credit: Joe Armao

In some regions of the Australian alps, particularly in Victoria but also in New South Wales, these stands of dead trees are replicated hill after hill, slope after slope, as far as the eye can see.

The gnarled, rugged branches of the beloved snow gum, one of the Australian public’s favourite trees, have evolved over millennia to weather severe winters, in places where temperatures can drop below -20 degrees and frosts can grip the landscape all year round.

Their unusually pliable branches can bend almost to the ground to bear the enormous weight of the snow that settles on them, making them the only tree that survives at these altitudes.

But the global climate crisis, driven by humans burning fossil fuels, has brought a new threat to these mountain peaks: more frequent and more intense bushfires.

Because snow gums have not evolved to cope with these conditions, experts say the nature of Australia’s high mountain landscapes are changing, and the ecological collapse of snow gum woodlands - the abrupt decline or change of this ecosystem - is happening before our eyes.

Ecologist John Morgan next to an old snow gum at Dinner Plain near Mount Hotham. Credit: Joe Armao

“Snow gum don’t like fire at all - as soon as you hit them with fire they have to start regrowing from the base,” explains La Trobe University’s Associate Professor John Morgan, as he runs a hand across the pink and green striated bark of a towering old snow gum. “And it takes them a long time to regrow these big trunks, probably over a century.”

Morgan, a plant ecologist, met this masthead in a patch of alpine bushland, dotted with elderly snow gums and fringed with younger ones, near the Victorian ski village of Hotham Heights, about 1450 metres above sea level, to show us what mature, old-growth snow gums should look like.

To regenerate after a fire, snow gums can resprout from buds under their bark, or from the large swelling at their base, known as the ‘lignotuber’. Partially buried, the lignotuber is where protected buds lie dormant until the tree’s canopy is lost, and vigorously re-sprout after fire.

Dead and living snow gums near Mount Hotham. Credit: Joe Armao

But their capacity to do this is limited, and every time a snow gum is burned some of these buds are lost: “There’s only so many buds on the tree from which to resprout,” says Morgan. “And it’s these multiple fires, not single fire events, that are really knocking snow gums on the head.”

Long-unburnt, old snow gum forests, which have significant conservation, eco-tourism and cultural value, are now exceedingly rare. They comprise only one percent of snow gum forests in the Victorian alps, according to a new paper co-authored by Morgan that will be published in the Australian Journal of Botany in the coming weeks.

A snow gum that has been attacked by wood boring beetles. Credit: Joe Armao

Researchers looked at the mountainous region along the Great Dividing Range to the east and north-east of Melbourne and made a startling discovery: only 0.5 per cent of these snow gum forests had remained unburnt since 1938, and 92 per cent had been burnt at least once since 2000.

Since 2000, the repeated incidence of bushfires has meant 30 per cent of snow gum stands have now been burnt three, four or five (or more) times since 1938.

Researchers found only three areas of old-growth snow gums had not burnt in 1939 or since; trees surrounding the historic chalet at Mount Buffalo, east and south of Mount Buller, and at Mt Nugong, in the Eastern Alps.

Although Australia’s alpine area is relatively small – covering about 11,000 square kilometres or 0.15 per cent of the continent – these alpine and subalpine ecosystems have outstanding natural value, and are home to thousands of plants and animals that occur nowhere else on earth, including the critically endangered mountain pygmy possum and migratory bogong moths.

An area near Mount Hotham which has been burnt in recent years, with Hotham Heights village in the background. Credit: Joe Armao

The last part of the drive up to Mount Hotham, along a steep road winding up from the village of Harrietville, is confronting: thousands upon thousands of white, dead snow gums thrust out of the forest of living, younger snow gums beneath them. Most visitors come to the alps in winter, when snow blankets these mountains and these changes are less obvious.

In theory, these younger snow gums will mature, produce seed, and sustain the next generation. But they need to be at least 20 years old to produce seed, perhaps more, and the odds of another bushfire sweeping through in that time period are shortening.

Otherwise, it’s like these young forests are stuck in toddlerdom; just as they begin to mature they get hit by another bushfire, and the forest has to attempt to start the cycle all over again.

Snow gums extend all the way from the central highlights in Victoria to Kosciuszko in New South Wales, and are also found in Queensland, South Australia and Tasmania. But the biggest impact on them is in the middle part of their range, in Victoria, where the really high frequency of fires are occurring.

Dr Tom Fairman, a forest scientist at Melbourne University, did his doctoral research on the frequency of alpine fires: “I remember looking at maps of fires and thinking ‘They’re starting to overlap, that’s concerning.’ There were only a few years between big, landscape-scale bushfires.”

Fairman surveyed snowgum forests, and mixed tree species forests, to find out how well they were resprouting, going into areas that had been burned in high-severity fires up to three times in a decade, in 2003, 2007 and 2013.

He found snow gums recovered after a couple of fires, but after the third one they really suffered, with a loss in the ability of the lignotuber to keep pushing out shoots.

After two fires the background mortality rate was about 10 per cent of the trees, but after three fires it jumped to half of them. At some sites it was as high as 80 per cent.

“I have some very distinct memories of sitting at the end of the day looking across a valley…that had been burned multiple times, and you could see the stems of the trees and underneath them mainly acacia shrubs and grass…it affected me quite deeply,” says Fairman. “I remember thinking ‘Shit, we have to start doing stuff differently. We have to confront this. We’re pushing things beyond a resilient limit for a species that is otherwise pretty tough’.”

Dead snow gums on the slopes near Mount HothamCredit: Joe Armao

Snow gums are the only tree species at high altitudes, and removing them will change the microclimate of the region, the composition of the soil and its permeability, says Morgan.

“It’s not like we get rid of snow gums and another eucalypt takes its place…it is the only species up here.”

Multiple fires lead to significant changes in the understorey of a snow gum forest, and grasses dominate rather than shrubby plants, creating a savannah landscape. “All these now dead trees we see around us are no longer carbon sinks, they’re sources of carbon emissions. That’s happening over a large part of the Victorian Alps,” says Morgan.

Cam Walker, from Friends of the Earth, stands in an area of bushland that was burnt two years ago.Credit: Joe Armao

We’re walking through an alpine meadow, spongy with thick mosses, sedges and grasses, with Cam Walker, the campaigns coordinator at Friends of the Earth.

Walker lives for part of the year at the ski village of Dinner Plain, near Hotham Heights, and joined the local Country Fire Authority brigade as a volunteer after the fires in 2016.

Evacuating from the village at the time, he saw three towering pyrocumulonimus clouds, generated by fire, stretching in a line southward: “I realised, this is the future,” he says.

Another mountain tree species, the lesser-known alpine ash, is in even bigger trouble than snow gums, also because of the frequency of fires, says Walker. But in its case the state government spent more than seven million dollars after the black summer fires to airlift tonnes of seed to the devastated forests.

Commensurate action has been taken on snow gums, says Walker, who estimates roughly a third of Victorian snow gum forests are under threat.

Walker, and the scientists we interviewed, want the state government to undertake a scientific survey and assessment of snow gum health, and actively protect the remaining areas of old-growth snow gums from fire.

And this would require a shift in the public conversation about what should be prioritised during bushfires, to include the protection of natural and ecological “assets”, as well as human ones.

The Wollemi pines saved by a secret fire fighting mission during the black summer bushfires.

There are some precedents for this. During the Australian bushfires of 2019-20, a team of remote area firefighters was successfully deployed to save the ancient Wollemi pines from the giant Gospers Mountain fire in New South Wales.

And a similar approach was taken during these fires in the Namadgi National Park, in the Australian Capital Territory, where bulldozers cut containment lines to prevent fire spreading into important unburnt vegetation.

The Victorian government has recruited more forest firefighters, but further investment is needed, including the establishment of a volunteer remote area firefighting team - Victoria is the only state on the east coast that doesn’t have one - and the purchase of a large airtanker.

It’s not all bad news, Walker is keen to point out, leading us to a patch of young snow gums that have flourished during the past three years of damp La Nina conditions. “What we know is these forests will come back, but only if you keep the fire out. It’s a very low intervention approach.”

A road near Hotham Heights winds through areas of burned bush and dead snow gums. Credit: Joe Armao

A spokesperson for the Victorian government said it conducts monitoring programs across the state’s forests to inform ongoing protection of its precious native ecosystems, including snow gum woodlands.

“Forest Fire Management Victoria also focuses on rapid response in sensitive environmental areas – this includes using helicopter rappel crews to access remote snow gum woodlands and alpine landscapes,” they said.

Understanding the damage wrought by fire on snow gum woodlands should sound an alarm bell for anyone who loves Australia’s alpine areas, says Walker. “It’s devastating. Like everyone else, I thought, well, we live in a country that’s built on fire. Everything is fire adapted. You think it will come back. But the problem is the frequency.”

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