As the planet warms and the population expands, so too does the need for trees.
Having enough trees in massive concrete-clad cities and sprawling outer-suburban developments is one key to keeping cool.
That’s why Sydney, Australia’s largest city, is set on an ambitious plan to expand its tree canopy cover in urban areas.
Sydney’s Lord Mayor Clover Moore says “urban forests” are vital for the city to remain liveable.
More than 16,000 trees have been planted in the area since 2004 and she thinks they are just as important as roads and broadband internet.
“We’re in the middle of a climate crisis and we’re already experiencing its impacts,” she said when announcing the plan last week.
“More shade in more corners of the city will help us to combat the urban heat island effect and better place Sydney to mitigate some of the worst impacts of extreme heatwaves.
“Effective and extensive canopy cover can reduce temperatures on the ground by up to 10 degrees.”
Central Sydney currently sits at 20 per cent green cover. The ambitious goal is to increase that to 40 per cent, with 27 per cent tree canopy by 2050.
What are the benefits of having trees in urban areas?
Dr Andrew MacKenzie, a member of the Australian Institute of Landscape Architects’ NSW Advocacy Committee, told The New Daily there are many benefits to increasing canopy cover in urban areas.
“I think the really important thing is that if you’re thinking about the value of tree plantings as a way of improving the quality of life, in cities, it’s very cost effective,” he said.
Street canopies reduce heat not just on the hottest days, but also lessen what is known as Urban Heat Island Effect (UHIE), Dr MacKenzie said.
UHIE happens when an area has a lot of roads, pavements, buildings and limited green infrastructure, which results in the heat being absorbed during the daytime and released at night.
“So you’re then not getting the cooling effect that night and over the summer that accumulates,” he said.
“Over time, and particularly during extreme heat events, like heat waves, the effect of of unshaded pavements, exacerbates heat, and heatwaves more than like they would otherwise.”
Black bitumen and dark roofs make UHIE worse. Canopy coverage, which can improve it, is also declining across Australia, according to a 2017 report.
Better for your mental health
The risk of health-related issues associated with extreme heat can be mitigated by having adequate street canopies, Dr MacKenzie said.
Mental health could also improve by increasing the amount of trees and greenery in urban areas.
“We’re kind of the kind of biologically hard-wired to enjoy looking at greenery and nature in the light,” Dr McKenzie said.
Every city needs a different approach
It’s important every city adopts a plan that is specific to conditions, Dr MacKenzie added.
For example, Canberra is cold in winter and hot in summer, so having deciduous trees would be best as they offer protection from the heat in summer while letting in the sun through bare branches duirng the cooler months.
“Almost every, city, major capital city, and even regional centres have tree planning targets, or they have what’s called green infrastructure plans,” he explained.
It’s best to think of green infrastructure plans as a way to provide the benefits of nature in a city and in the country, he added.
“We have very diverse cultures and backgrounds, and people’s perception of nature also vary greatly,” Dr MacKenzie said.
“So while you might look at a natural scent, and think of it as being attractive, other people might find it messy or terribly frightening, so poorly designed tree planting can be actually quite isolating.”
He said it’s important the community is consulted.
Broadly speaking, a community will want more trees, but things like street parking need to be considered.
