“Bigger, healthier trees”: Why protecting our greenery is the key to driving down heat

While the State Government’s announcement of new planning protections around trees was a positive step, there was still a “huge shortfall” in the state’s investment - about $2 billion - needed to achieve the state’s 30 percent canopy coverage targets, according to an urban planning researcher.

🛑 Better protections: On September 15, the State Government introduced an amendment to all state planning schemes, with the new clause requiring a planning permit to remove, destroy or lop a “canopy tree” in specific circumstances.

A canopy tree is a tree that is higher than five metres above ground level, has a trunk circumference of more than 0.5 metres and a canopy diameter of at least four metres.

🌴 More green, less grey: RMIT’s Thami Croeser told the Eastern Melburnian that urban construction materials had a high thermal mass, meaning they can absorb a lot of heat, and that air in urban areas can be eight to 10 degrees hotter than rural areas.

“Tree canopy is an antidote to that,” said Croeser, a Vice Chancellor’s Postdoctoral Research Fellow at RMIT’s Centre for Urban Research.

🌡️ Heating up: According to the first ever National Climate Risk Assessment report, we currently experience four days of extreme heat - where the average Australian temperature is in the top one percent of records - a year. The report showed this would increase to 18 days per year under a 3°C warming scenario.

Global warming is currently confirmed at 1.2ºC above the pre-industrial average temperature from the late 1800s. However, warming across Australia has already reached 1.5ºC.

🌇 Local development: Croeser said while more housing was needed, greenery needed to be  incorporated into new developments, particularly those around planned new Suburban Rail Loop East precincts in areas like Glen Waverley and Box Hill.

“If we take out everything within a 300-metre walk of these stations and densification precincts, and it just becomes wall-to-wall big buildings, that means every bit of private tree canopy and backyard [are] lost,” he said.

“We need (the tree canopy) to go up, not down, which means bigger, healthier trees and more of them, not cutting them down whenever we build a house.”