As Christmas draws to a close, many Australians are beginning to think about their tree, but the question is not what to cut or how to prune it.
In a new study, the authors looked at tree canopy in a number of Australian cities over the past century and found that the changes in tree cover have been gradual.
While trees are growing in the tropics, there is little change in tree density, they report in their study, which was published in the journal Science Advances.
“The tree is getting smaller,” said lead author David Macdonald, a tree scientist at the University of New South Wales.
And that’s probably not as bad as people think.” “
But it’s still pretty small compared to the canopy.
And that’s probably not as bad as people think.”
They say the changes are likely due to the rise of urbanisation in the past decade and the increasing number of people living in urban centres.
“There’s a lot of evidence from the climate change research community that the forest canopy changes as cities expand,” said Macdonald.
“So we’re really hoping that the increase in the urban population will help offset that, and we’re looking at that now.”
Macdonald and his colleagues looked at five cities across Australia over the 20th century, including Melbourne, Adelaide and Canberra.
They looked at the number of trees in each location, and the changes from year to year in tree canopy.
They then looked at trees that were growing at the same time, and calculated the annual change in the total canopy.
“We used tree density to track tree growth, and that allowed us to see the tree growth rate of each location,” said study co-author Dr Michael Taylor, a plant physiologist at the Australian Museum.
Changes in tree size in the 20s and early 30s The authors found that trees in Sydney and Melbourne grew in size from the early 1930s through the mid-20th century. “
Because there was a lot more tree growth in the early 20th and early 21st centuries, the canopy has changed quite significantly over the century.”
Changes in tree size in the 20s and early 30s The authors found that trees in Sydney and Melbourne grew in size from the early 1930s through the mid-20th century.
“Tree density had really picked up in the mid to late 1930s, but there was no change in growth rates until the mid 1990s,” said Taylor.
There was also no increase in growth in tree mass, the study said. “
What was interesting is that the tree density of Sydney is not significantly different from the density of Melbourne or Adelaide, which indicates that there may have been a gradual increase in trees over time.”
There was also no increase in growth in tree mass, the study said.
“This indicates that, at least in the Melbourne area, there was relatively little change from the mid 1980s through to the mid 2000s,” the authors wrote.
The authors said that tree density changes may have occurred because of the urbanisation that occurred over the same period, with cities growing taller and wider.
“Over time, tree density has increased substantially,” said Professor Brian Loughlin, a research fellow at the School of Earth, Ocean and Atmospheric Sciences at Monash University.
“And that’s the case across most of Australia, even though there is some regional variation.”
He added that it is likely that the trend is not the result of urban growth, as there has been a “small increase in urbanisation”.
“Urbanisation may be the cause of some of the observed changes in trees, but it’s probably more likely that it’s the result, in part, of urbanised people being in cities,” said Loughton.
“Urban people have moved into cities and they’ve used the space available to grow and foraging.”
Loughland said the study also looked at changes in the climate, with the researchers comparing trees from different locations in different years.
“Our main takeaway is that there is no evidence of climate change forcing changes in canopy,” he said.
This may be because of climate variability, such as the El Niño event.
But Taylor said it may also be because there has not been enough time for the tree to recover.
“People have to be thinking about the impacts of climate on their tree,” he added.
“You have to have some level of knowledge of how the climate works.”
He said it was important to remember that trees can survive in the changing climate for decades.
“If you’re in Sydney, you’re going to be able to see a lot different species of trees growing in Sydney,” he noted.