What’s killing the mighty gums?
Dead eucalypts litter the Monaro landscape and now the Snowy Mountains gums are in trouble.
There’s a photo that 16-year-old Ivy McGufficke likes to look at every time she returns to her family farm near Cooma after a term at boarding school. It’s 2005 and two-year-old Ivy is standing in a sheep pen wearing a blue jacket, holding a half-eaten sandwich in one hand and in the other an old sheep pellet tub, repurposed as a peg bucket. Her destiny is already sealed; the youngest of three daughters born to Monaro graziers Alan and Michelle McGufficke, she will grow up as connected to this land as the merinos that poke their woolly heads over the sheep race alongside her.
But it’s what’s in the background of the photo that keeps drawing her eye. It’s the trees. They rear up behind her, dwarfing the wide-eyed farm girl — mighty Eucalyptus viminalis, commonly known as manna or ribbon gums. Their canopies are full and green and along the length of their trunks thin strips of bark peel away like streamers at a birthday party. Her first memories are of playing under those trees, digging up pieces of crockery and tiny animal bones in the soil, climbing the strong branches.
But as Ivy grew stronger the trees grew weaker until each one of them shed its leaves and died. Her games evolved to hiding in the rotting hollows, collecting fallen birds’ nests that the canopy could no longer cradle, filling wheelbarrows to cart away dead wood for bonfires. The bushland of her childhood went from an enchanted forest to next year’s firewood. Today, her mother Michelle describes their farm as looking like Hiroshima. “It’s like a nuclear blast has come through. People come here and say, ‘What have you done with your trees?’ They must think we poisoned them.”
But it wasn’t just their place. Next door, farmer David Whiting lost all his ribbon gums. So did Jim Litchfield down the road. In fact, ribbon gums have died on a huge scale through a sort of Bermuda Triangle of death in the Snowy Mountains region between Cooma, Nimmitabel and Jindabyne. Across 2000 square kilometres — an area about the size of the ACT — every last ribbon gum is dead or dying, leaving a desolate landscape littered with skeletal remains and bony branches jutting against the sky like fork lightning. The dieback has taken an emotional toll on the people of Monaro and on those who visit this unique Australian landscape, or pass through on their way to the snow. Want to see a ghostly vision of the future? Take a drive from Cooma to Jindabyne.
The wave of destruction was quick and brutal, first observed around 2005 and escalating over the next five years. Dieback is not uncommon but this recent event is now recognised as one of the most significant and mysterious ever to hit Australia. And worse could be yet to come. Up in nearby Kosciuszko National Park, the iconic snow gums are showing signs of going the same way, as are others in the ACT and Victoria. Scientists don’t know where it will end because they don’t know where it started, or why.
“It’s the size and scale of this dieback that makes it stand out,” says associate professor Cris Brack from the Australian National University. “It spread to 2000 square kilometres before anyone really noticed. That’s the scary thing. It was also species- specific. It hit ribbon gums and nothing else.” Not that there was much else for it to hit. The ribbon gums largely ruled alone in rocky, inhospitable outposts. Like castles, they occupied hilltop strongholds atop weatherbeaten granite knolls and ridgelines, commanding a stable presence over the naturally treeless basalt plains to the west.
Brack says he spent years trying to rouse interest from government with no success — no department thought it was their responsibility. In 2015 he and an honours student, Catherine Ross, conducted what is still the only study of the dieback. They swiftly found a suspect: a eucalyptus weevil was devouring the leaves. Trees have a way of dealing with insect attack: if a eucalypt loses its crown it will shoot out fast, new growth known as epicormic foliage. These new leaves provide the tree with a kind of sugar hit — enough energy to start repopulating its depleted mature leaves. But if the insects keep attacking, eventually the tree gets stuck in a lethal loop. It runs out of the energy stores needed to flush out new growth, and will eventually succumb and starve to death.
So, a weevil was implicated in the dieback. Case closed? If only it were that easy. This is a native insect, meaning the trees have evolved over millions of years to cope with it. Why, then, were they suddenly powerless to defend themselves? Why didn’t they have the energy to fight back?
“There’s always been a war,” says Brack. “The trees are always trying to stop their leaves getting eaten and the weevils are always trying to work out how to eat them. It’s been in balance forever. But something has thrown that balance out.” Something else was going on.
Brack and Ross set up a batch of experiments — eight study stands of trees in a diverse array of environments within the dieback area. They compared stands in grazed areas and ungrazed areas; stands that had been fertilised with ones that hadn’t; stands where the water was good with stands where the water was bad; stands that had been burnt to a crisp with ones that had dodged bushfire. “The expectation was that one of the stands would be worse than the others if there was a culprit,” says Brack. But what they found was dead trees everywhere, uniformly across all the stands. It yielded no clues.
Brack can’t rule out the root-rot pathogen phytophthora, responsible for killing New Zealand’s famous kauri trees and the jarrah forests of Western Australia, but he says the Monaro doesn’t fit the pattern of phytophthora dieback. The study’s conclusion, if there was one, was that the millennium drought led to such high levels of water stress that the trees, already at the limit of their range in terms of water and temperature tolerance, didn’t have the strength to fight off the weevils. Seems plausible. But then the drought broke and the trees kept dying. And now it appears the weevils have gone; none has been spotted since autumn. Brack’s summation is difficult to refute: “It’s all very strange.”
Spring snow has painted the Main Range white.Up at Dainers Gap, not far from Perisher ski resort, Matthew Brookhouse, senior lecturer from the Australian National University, is trudging through the drifts. His footsteps in the snow trace a path from tree to tree, camera and notebook in hand. Here, it’s our highest altitude trees, Eucalyptus niphophila, that are in trouble. This time the government’s listening, for these are the trees featured in a thousand landscape photos, the trees strewn throughout our country’s largest alpine resort, visited by three million tourists every year. They are our iconic snow gums.
A different type of insect is applying the fatal blow here. A species of Phoracantha, a native wood-borer, is ringbarking the trees. In Perisher you see their handiwork everywhere: cracked and dead bark, bore holes and the distinctive, deep horizontal channels in the trunk. It’s not just the niphophila dying, either — every sub-species of snow gum is showing signs of dieback over a huge area, from Long Plain in the northern region of the park to the top of the Brindabella Range in ACT and south into the Victorian Alps. “We know it’s widespread, it’s consistent and it’s the same insect damage,” says Brookhouse. “We just don’t know what’s driving it.”
Picking it up early gives Brookhouse some hope. “The situation we don’t want to be in is the one we’re left with down the road: a landscape littered with dead trees, and us still asking questions why,” he says. “These trees are part of the living culture of the Snowy Mountains, and we’re watching them die. We’re talking about a species that has nowhere left to go.”
Starting in summer, Brookhouse will lead a comprehensive survey to map the full extent of the declines and establish long-term monitoring plots. The public can help too, via an online mechanism to report tree damage, uploading photos to the online Atlas of Living Australia. Brookhouse is worried these aren’t isolated instances of dieback, but something much greater in scale. “Some people think there is a distinction between decline and dieback. I tend to see dieback as part of a continuum of decline. It’s the extreme end of a general decline in health of the ecosystem. I don’t think anyone would have forecast that almost every viminalis on the Monaro high plains was going to die. You’d have been called alarmist if you had predicted that.”
No closer to getting answers, I spend the night with friends — farmers from Jindabyne. Hanging on the wall in their kitchen is an old aerial photo of a typical chunk of Monaro countryside. The land is cleared of trees apart from a few pockets here and there — stands clustered on rocky hilltops or deep gullies, which, by virtue of their awkward position, escaped land-clearing. In the photo the trees stand isolated, huddled together without the protection or companionship of the former forest. These are the doomed viminalis.
Companionship? The word might sound odd, but it’s accurate. We know now that trees are linked below ground by a sophisticated network. They feed each other, pumping sugar into struggling neighbours, and communicating dangers (such as insect attack) via chemical and hormonal messages so that other trees can rally their defences. When those social networks are cut off, trees lose their ability to communicate. So trees need other trees around them — the more the merrier — for an efficient ecosystem. Together their canopies can protect each other from extreme wind, stop the heat of summer scorching the forest floor and help the whole community store more water and generate humidity. In other words, a forest creates its own ideal habitat.
After surviving the massive clearing, the remaining viminalis here would have had to cope with the sort of conditions that no tree could be expected to endure. Grazing brought with it massive erosion, stripping the topsoil, compacting the ground and squeezing out moisture like a weight being lowered onto a sponge, turning soft soil to ceramic. Surface water formed into rivulets, which in time became deep gullies, instead of soaking into the ground. Rising water tables sent salinity levels soaring. The application of superphosphate brought artificially high levels of nutrients to the soil, interfering with the trees’ natural nutrient and sugar distribution systems. Native grasses were replaced with pasture grasses, resulting in lost biodiversity. That’s before we even start talking about climate change and drought.
I stand back from the aerial photo and let a few things sink in. Viewed through the prism of history, the Monaro dieback suddenly starts to make some sense. Once you realise the dead ribbon gums weren’t always straggly, lone soldiers but part of a huge, interwoven bushland, their eventual demise seems plausible, even inevitable. It also makes the wider prognosis far more ominous. If disrupting just one element of an ecosystem can start a snowball effect, what happens when virtually every part of it is up-ended? Maybe we’re beginning to find out.
The underground is often overlooked. Peter Marshall is a forest mycologist — a fungi specialist — who rehabilitates degraded land. A graduate of ANU’s forestry school, he has a special interest in the symbiotic relationship between tree roots and a type of subterranean fungi called mycorrhizae. Marshall says foresters have underestimated the importance of this relationship. “Without it,” he says, “our forests would be dead.”
A mycorrhizal relationship is a beautiful thing. The fungi wrap masses of tiny filaments called mycelia around a tree’s roots; ideally, every rootlet will be completely encased in the fungus, so that the roots themselves won’t even touch the soil. The mycelia spread out like a web through the soil, connecting with other trees’ roots and forging a sophisticated underground network. The benefits for the tree are enormous. The mycelia can get into places roots can’t, increasing the area of absorption for the tree hundreds or thousands of times. The fungus will seek out nutrients and water to give to the tree, or to exchange with other trees, protecting the roots from pathogens, filtering out heavy metals and allowing for information to be shared between trees. Working together, the fungi and the tree can tap into the richest sources of underground nutrients and water. In exchange for these essential services the tree feeds its mycorrhizae sugar, which keeps it alive. If the fungi die, the tree is effectively left groping around blindly.
“The system has evolved over 100 million years and is utterly crucial to the success of Australia’s landscape,” says Marshall. He suspects a huge reduction in mycorrhizal fungi has had a drastic effect on the health of trees everywhere. “It’s not just Monaro. Once you know where to look you’ll see it everywhere. Drive from Canberra to Yass — there are no healthy trees.”
Professor James Trappe from Oregon State University agrees the literature on subterranean ecosystems is too often ignored. “We know that if there’s damage to the soil and the mycorrhizas it sets the trees up for damage from insects. If trees are under stress — whether it be drought or insect attack or whatever — their ways of overcoming that stress depend on having a good root system.”
Fungi and their associations with eucalypts are poorly studied in Australia, says Todd Elliott, a mycologist at the University of New England. “We don’t have a baseline, so we don’t know what it was like 50 or 100 years ago. But we do have a lot of compelling evidence internationally about what happens to ecosystems when you disrupt this relationship, and if that wasn’t a big part of what’s going on here in Australia it would be very much an outlier.”
Mycorrhizae are spread through the distribution of spores from their fruiting bodies — mushrooms or truffles (a handful of species of which are prized by gourmands). Marshall says all healthy eucalypts have mycorrhizal partners on their roots. Australia has the greatest truffle diversity of any continent, with more than 2000 species. But the way in which they reproduce in Australia has been catastrophically impaired.
A truffle is not only a delicacy to humans. The intense aroma and taste is irresistible to small foraging native mammals such as potoroos and bettongs (also known as “rat kangaroos”), which dig them up, eat them and spread the spores through scats. An eastern bettong’s diet is 90 per cent truffle, and they have a particular fondness for truffles associated with eucalypts. Their digging tills the soil, oxygenating it and distributing nutrients, improving water infiltration and seed dispersal, and speeding up the breakdown of organic matter. Rat kangaroos are known as “ecosystem engineers.” Unfortunately for our ecosystems, the engineers have left the worksite.
About 30 native mammal species have become extinct since European colonisation. Bettongs were deemed vermin by early agriculturalists (it was said you couldn’t grow potatoes in the ACT because bettongs would immediately dig them up). Bounties were paid on nearly three million between 1880 and 1920; then, during the 10-15 years it took for foxes to colonise the bulk of NSW, they were totally annihilated. Eastern bettongs survive in the wild only in Tasmania, where there are few, if any, foxes. They’re now known as Tasmanian bettongs.
At Mulligans Flat Woodland Sanctuary in Canberra’s north, researchers are attempting to wind back the clock. A 1.8m-high electric fence encloses a 485ha native utopia. Safe from foxes and cats, Tasmanian bettongs and eastern quolls have been reintroduced to dig among the gums, and both trees and animals are thriving. ANU professor Adrian Manning hopes the bettongs may help initiate and accelerate a transition back to how things are supposed to be; literally digging us out of a hole. “The loss of the bettong is not explicitly mentioned as a threatening process… yet any native tree over 120 years old in remnant box-gum grassy woodland almost certainly germinated in soils turned over by this, and other, native ecosystem engineers,” Manning says.
At Mulligans Flat it was discovered that a single bettong moves around 2.8 tonnes of soil a year, and Manning says predator exclusion coupled with small mammal reintroduction could be our most significant and cost-efficient step towards ecosystem restoration. However, an attempt in 2017 to release 67 bettongs from Mulligans Flat back into the wild failed. All were dead within eight months. The message is clear: you can have foxes or you can have bettongs, but you can’t have both. To what extent the loss of ecosystem engineers can be blamed for the Monaro dieback is open for debate, but it could have weakened the trees just enough that they succumbed to the drought and the insects. And with margins this tight, that’s all it would take.
Out in David Whiting’s paddock, next door to the McGuffickes’, new life grows from the graveyard. Among the dead viminalis a 1ha fenced-off plot is dotted with newly planted trees. It’s part of a trial to repopulate these barren hills with a new generation of gums brought in from different regions in south-eastern Australia.
There are currently eight “provenance plots” in the dieback area. “Ten years ago we would have planted the same trees we lost,” says Nicki Taws of Greening Australia. “But now we’re thinking we need to plant seedlings today that are going to survive to tomorrow. It could be that there’s a viminalis from western Victoria that’s better adjusted to a warmer climate, or even from Tasmania.” The hope is that as the trees grow they will cross-pollinate, resulting in a “hybrid” suited to the area. The CSIRO, which is helping to design these revegetation plans, calls it “climate-adjusted provenance”. Along with replacement ribbon gums, Greening Australia has planted snow gum, candlebark, blackwood wattle and silver wattle.
“It’s definitely trial and error,” says Taws. “I don’t want to play God and say, ‘This tree is done for’. But if we don’t set this up now then in 20 years we still won’t know. That’s the trouble with trees, it’s a 10, 20, 100-year experiment.” Taws feels for the farmers, who have had to watch the calamity unfold on the land they love so much. “For them, this is personal. The drought is one thing, but to know that the trees are dying too makes for a lot of despair.”
Upper Snowy Landcare is working alongside Greening Australia on the replanting, spending $250,000 to establish 17 biodiversity plots across the dieback area, including one on the McGufficke farm, with 11 more sites planned. USL secretary Margaret Mackinnon says it could be that viminalis are just not viable here anymore, so we need to find out what is. She, too, points to the drought as the underlying problem. “With climate change the first species to go will be the ones living on their environmental margins. Viminalis areeverywhere but the only ones dying are in this area. And if you look at rainfall in that area you’ll find that the dieback completely overlaps with a big rainfall hole. It’s the driest part of the Monaro so the viminalis are right on their margins.” Mackinnon says she feels like she’s living in an “environmental garbage tip” and agrees with Marshall that we should also be looking at the role of soil fungi. “The Monaro’s soil is comatose. You go out into these paddocks and there’s no organic matter, no life whatsoever. This land needs a serious reboot.”
Grazier Jim Litchfield thinks his trees might already be getting a reboot, just from destocking. Since removing stock from certain dieback-affected paddocks he says he’s noticed the ribbon gums bouncing back. “We’re conscious to fence off any wooded areas now. I think it’s a land management issue: stock and overgrazing.”
Litchfield was ahead of the game. He fenced off a vacant plot 30 years ago and planted snow gums. Today the trees are tall and full of life, although it’s likely to have been a different story if he had planted ribbon gums. “You’ve got to try something,” he says, casting an arm over the haunting expanse of dead gums, with their dead, scrawny branches the colour of sun-bleached driftwood. “Otherwise you end up with this.”
Ivy McGufficke doesn’t blame anyone. It’s what happens next that matters. “Growing up I remember thinking, this was just how trees were supposed to be. I thought it was normal for trees to slowly fade to grey, then go stiff and bald. Nature doesn’t have a choice anymore to naturally restore itself. We as humans have caused this and we have a responsibility to fix it. We’ve become so reliant on nature to provide for us, but we haven’t given enough back to nature, so nature can’t rely on us.”
She returns the old photo of herself to the album, which includes one of her sister Florence on an old truck at the base of a hill covered in healthy gums. School holidays are nice but there’s always work to be done on the farm, always something to worry about. She looks out the window to those beautiful, granite-specked hills and wonders what the photos of the future will show. The memories of tomorrow are made today. This is her generation’s challenge. “We have to get better,” she says. “Our actions need to benefit something bigger than ourselves. Sometimes I think we’re so caught up in trying to save the planet, we’re blind to what’s happening in our own back yard.”