In what might be a sign that more people are coming to understand the value of old growth trees, environmentalists and others were shocked this week at images of a more than three-metre-wide tree in Tasmania’s Florentine Valley being trucked off to a chipper.
These trees have been legally logged and removed for many years, but the image of the old tree on a log truck moved many more people on social media to ask why it was chopped down.
Part of the tree – likely a mountain ash (Eucalyptus regnans) was photographed on the back of a truck in the south of Tasmania.
Statements circulated by the state government owned Sustainable Timber Tasmania indicated the tree was felled for safety reasons.
However, attention to the loss of native trees for timber is being increasingly emphasised in Australia with moves by the Victorian and Western Australian governments to bring the practice to a close, in line with South Australia and the ACT.
A recent scorecard published by WWF Australia criticised the nation’s world-leading rate of land clearing.
While safety is a consideration for forest managers, there may be other interventions to prevent particularly large and valuable trees from being felled.
“In forests, it will depend on the tree and how often people are in its vicinity,” says Dr Greg Moore, an arborist who was a long-standing principal of Melbourne University’s horticulture-focussed Burnley College.
“Trees are often removed because of perceived risk rather than any real risk. Trees are also removed before other options of mitigating risk are considered.
“Large old trees are often removed unnecessarily because they are undervalued, when their value in every sense is very high.”
So what’s the value of a large and old tree?
Trees provide numerous ecological benefits to ecosystems, but particularly to humans.
These services go beyond their role as natural lungs that convert carbon dioxide into oxygen. Trees are important nutrient cyclers for soils, support water systems, and provide habitat for animals.
Old trees are particularly important. Holey, hollow-bearing trees are preferred by many animals, but these cavities can take upwards of a century to emerge, so their loss and replacement can take decades to provide suitable habitat again.
Tree-felling can have literal knock-on effects by damaging lower levels of vegetation once a trunk hits the ground.
Beyond this, old trees provide exponentially more carbon sequestration benefits than smaller ones.
As well as being large carbon stores – an important function for humans amid calls for dramatic cuts to carbon emissions – a study by the US Geological Survey in 2014 found large, old growth trees continue to fix carbon at greater rates than smaller ones.
“A tree of 3-metre diameter provides vastly more services in general than trees of smaller diameter,” says Moore.
“In Australia, we often note that for each large old tree, there are at least 30-50 other species – insects, birds, reptiles, fungi. This might seem a lot but it is probably an underestimate. An English study of one old oak tree recorded 2000 different species associated with it.
“In terms of carbon there have been studies revealing that one old oak would need 48,000 seedling oaks to sequester the same amount of carbon. This just 2 of the many services that trees provide.”
Originally published by Cosmos as Big Tassie tree a crucial natural service off to the chipper
Matthew Ward Agius
Matthew Agius is a science writer for Cosmos Magazine.
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