There is ever growing evidence of the impacts of climate change on natural ecosystems. We know that, without meaningful action now, the future of alpine vegetation in Australia doesn’t look good. This is true around the world. For instance, research shows that, in many instances, forests in the western part of the USA are not growing back after wildfire, and warmer temperatures are being blamed.
Here in Australia, longer and hotter summers are increasing the risk of longer fire seasons. Some parts of the Alps have been burnt three times in the space of a decade or so, with resulting impacts on what species grow back.
In the case of the upper Ovens valley, scientists have warned that without human intervention (aerial seeding) the alpine ash forests will start to disappear in the area if fire frequency continues as it is.
Now additional information has come to light about the possible collapse of mountain ash ecosystems in the Central Highlands of Victoria. Mountain Journal has previously reported on this but an article in The Age newspaper reporting on research by two of Australia’s most respected ecologists, David Lindenmayer and Chloe Sato, has pushed this information to a broad audience at a critical time in the campaign to see the Great Forest National Park established.
They point out that much of the Central Highlands have now been logged or burnt, meaning that the public land forests are mostly composed of young trees, which are much more flammable than old trees. This means the whole forest is at much higher risk of a huge blaze, which is consistent with the recent findings of Philip Zylstra.
They suggest that, as the mountain ash community collapses, the forests will be transformed and become dominated by acacia woodlands rather than the towering hardwoods that we currently know.
Liam Mannix, writing in the Age newspaper reports:
Victoria’s vast mountain ash forest in the central highlands is on the brink of collapse due to logging, fire and government inaction, a new paper argues.
And a future collapse could threaten Melbourne’s water supply, the paper claims.
But experts and the government have slammed the paper’s claims as sensationalist, saying the forest is fine and Melbourne’s water supply is not under threat.
This forecast comes from a study published on Tuesday in top international journal PNAS and written by two scientists based at the Australian National University.
Professor David Lindenmayer and Dr Chloe Sato say the forest has lost the ability to sustain itself.
Professor David Lindenmayer and Dr Chloe Sato, two of Australia’s most respected ecologists, have been tracking the plants and animals of the forest since 1983, publishing more than 200 papers along the way.
“It’s been very distressing to watch,” Professor Lindenmayer says. “Many, many of these sites that should have animals no longer do. To see many of the big trees that were there gone – that’s quite difficult to witness.”
In the paper, they argue the ash forest has lost the ability to sustain itself. They estimate its probability of collapse at about 90 per cent in the next 50 years.
About 80 per cent of the entire forest is now designated for logging, they claim – although this figure is hotly disputed. On top of that, huge swathes of the park have been consumed in bushfires.
The paper says the number of large, old trees in the forest almost halved between 1997 and 2011. The number of Leadbeater’s possums and greater gliders has more than halved. There are many fewer birds, including kookaburras, rosellas and honeyeaters, the paper says.
Almost 99 per cent of the forest is now young trees. Trees tend to reproduce mostly when they are very old, says Professor Lindenmayer. Without old trees, there are no new trees.
Young trees are also much more flammable than old trees. This means the whole forest is at much higher risk of a huge blaze. And if one struck, the trees would not grow back, the paper finds.
The trees would likely be replaced with wattle and acacia shrubland, which would be very bad for Melbourne’s water supply, the paper finds.
Some of the city’s reservoirs – the Upper Yarra Reservoir, the Maroondah Dam – are right in the middle of the forest. Rain falls on the trees and filters into the dams.
But young trees soak up much more water than older ones to fuel their growth. Replacing the ash with shrubland would “take enormous quantities of water out of the system,” says Professor Lindenmayer.
Melbourne Water, the authority on the city’s water supply, did not respond to repeated requests for comment.
But Professor Rod Keenan, from Melbourne University’s school of forest sciences, slammed the paper.
“It is not very rigorous – and I am surprised it was accepted for publication in this journal,” he said.
The paper relies largely on one marker to predict collapse: the number of old trees in the forest. Government datasets show the forest can recover, and that animal numbers have not fallen as dramatically as claimed. This paper ignores them, says Professor Keenan.
About 70 per cent of the park is protected from logging, he claims.
“The senior author has been a vocal advocate for a cessation of timber harvesting and creation of a new national park in this region for some time,” he said.
A spokesman for the Minister for Energy, Environment and Climate Change, Lily D’Ambrosio, said logging was allowed in less than 1 per cent of the state’s water catchments.
Large areas of the mountain ash forest were available for harvesting, the spokesman said, but all old-growth sections were protected.