Published in The Australian Oct 5 2019
As a year 11 student in 1989 Matthew Brookhouse was on an Outward Bound course that nearly went terribly wrong. Camping at Long Plain near Yarrangobilly in Kosciuszko National Park he caught hypothermia and lost consciousness. He was miraculously revived by friends and when he woke the first thing he saw was weeping snow gums, their marbled trunks spiralling skywards out of the snow like wisps of smoke from a camp fire. It was the most beautiful thing he’d ever seen.
Now a senior lecturer in ecology at Australian National University, Brookhouse dreads what he’ll find when those same trees shake off their winter coats and prepare to face another long dry summer. He knows many will be reduced to bare bones – dried up, brittle branches cracking in the sun, never to grow a leaf again – because many already are.
Our snow gums are dying. A native longicorn beetle is ringbarking the trees all across Kosciuszko National Park. The destruction wrought is stark, and it’s not just here in our most famous alpine national park. Throughout the Australian Alps across NSW, the ACT and Victoria snow gums of all species are facing an outbreak of dieback, and no one can say for sure why.
“It’s really upsetting,” says Brookhouse. “We know that it’s widespread, it’s consistent, and it’s the same insect damage. We just don’t know what’s driving it. So it’s hard to know where it’s going to end.”
First noticed in April this year, scientists are worried we could be facing a repeat of the devastating dieback that has killed nearly every ribbon gum (also called manna gum) in an area roughly bordered by Cooma, Jindabyne and Dalgety and left a 2000 square kilometres wasteland of dead trees. The Monaro dieback, as it’s now known, crept up insidiously before anyone really noticed it was happening. Brookhouse is determined not to let that happened with the snow gums.
“We need to act now. We don’t want to be left scratching our heads in 20 years time.”
A different insect, a native leaf-eating weevil, attacked the ribbon gums. But the problem goes much deeper than insects, who are merely finishing off the weakened trees. Brookhouse suspects the snow gums are drought-stressed, with their dry trunks making easy pickings for the woodborers. This summer Brookhouse will lead a research team to survey the extent of the snow gum declines across the Australian Alps, the true extent of which is still unknown.
“We need some serious data-gathering,” says Brookhouse. “We’ll be opening up an online mechanism for the public to report tree damage. We need people to help us with observations.” The team will investigate moisture stress in the trees, establish long-term monitoring plots and perform an insect survey. Brookhouse says we know the genus doing the damage – phoracantha – but we don’t know the exact species.
What scientists do know about phoracantha is that they go for drought-stressed trees, targeting dry trunks. A moist trunk acts like a moat, drowning insect invaders. Brookhouse suspects shorter winters could be playing a part in drying out the trees. An early spring means the trees suck up available water earlier in the season, putting on a quick growth spurt. But trees are not always great at rationing scarce resources. Come mid-summer they could have exhausted their water supply, allowing the wood-borers to burrow in.
“It’s devastating, says Brookhouse. “These trees are symbolic of a remote and wild place. They’re an emblem for wilderness, and we’re watching them die. It feels like I’m losing a part of myself.”
