Almost half of the plants and trees in Perth are facing extreme stress conditions and are in a far worse state than they were this time last year, according to research from UWA.
UWA associate professor Sally Thompson runs a research project that found that 45 per cent of Perth’s plants and trees were turning brown, had wilting leaves or were even dropping entire limbs.
The project involves an app that members of the public can use to flag stressed trees around Perth that the researchers then investigate. The current state of the identified trees is compared with satellite imaging to get a better idea of the health of Perth’s trees.
Most of the submissions have focused on five types of trees: with Jarrah, Tuart, Marri, Peppermint trees and Queensland box trees being the most affected.
She has received thousands of responses from the public, many sharing their concerns and personal stories about the trees.
She said: “We just got a lot of personal contact from individual people who would call me and tell me the stories about what they were saying in their neighbourhood, or they would post on our social media with stories about what was happening.”
“I had a really strong sense that people wanted to connect around this issue.”
Dr. Sally Thompson
Perth has the lowest amount of canopy cover out of all the Australian capital cities averaging only 16 per cent and shrinking, according to mapping done in 2020 by the WA Department of Planning, Lands and Heritage.
Dwindling trees also leave Perth susceptible to heat waves, as a lack of shade exposes the city to increasingly hot temperatures. According to a 2020 RMIT Centre for Urban Research study, the removal of tree canopies can make cities four to ten degrees hotter than their surrounding areas. This phenomenon is known as the urban heat island effect.
Curtin University professor of sustainability Peter Newman said that although some of the older suburbs in Perth are very green with big established trees, the urban heat island effect was at its worst in Perth’s newest suburbs.
Professor Newman explained that the issue lies in many developers using black roofing and destroying pre-existing trees for new developments. These houses absorb heat through their roofing and the suburbs don’t have a single tree in any yard or on the street to provide shade.
He reckons that developers should be required to plant street trees instead of leaving it up to councils, so that home buyers get already established trees on their streets.
“It’s a genuine problem for the city, because it was always thought that these new outer suburbs would be the garden city of the future. But they’ve got less and less trees each time. So the developers have never been able to actually produce anything more like a garden, let alone a forest. And that’s what’s really needed.”
Professor Peter Newman
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