The benchmark – increasingly being adopted in urban planning in Europe – suggests every home, school and business should be within view of at least three trees, be in a neighbourhood with at least 30 per cent canopy cover and be within 300 metres of a park.

While buildings in inner Sydney and Melbourne were often within view of three trees, having adequate canopy cover was rare.

“It’s the first time we’ve got a real benchmark on how much nature we need in cities … and I was just so shocked to realise how far we fall short,” Croeser said.

Only Seattle and Singapore passed the 30 per cent canopy benchmark, with 45 per cent and 75 per cent of buildings in these cities enjoying adequate shade, respectively.

“We put trees in a hole in the footpath,” Croeser said. “That footpath is made of crushed rock underneath the paving, and there’s almost no water getting to that tree, and the soil underneath is very limited.

“So you’ve got trees that, effectively, are starving or thirsty all the time, and their roots are struggling to find a place to grow.”

Karyn Brown has lived in Sydney’s Waterloo public housing estate, surrounded by mature eucalypts and melaleucas, for 25 years.

For Brown, the beauty of her home has been enhanced by the coolness and shade offered by the trees and the wildlife they bring.

“Oh, I love it. I particularly like the birds, they sit on my balcony sometimes on the fourth floor … eastern rosellas, magpies, white cockatoos and corellas.”

But the estate is earmarked for redevelopment, which will almost certainly mean the loss of many mature trees. “Most of the trees will be taken away, and most of the new buildings will go right up to the footpath,” she said.

Nicole Vickridge is an urban horticulture masters student at the University of Melbourne, and a researcher with NGO Sweltering Cities, which campaigns against built forms creating extreme urban heat.

Vickridge said tree-lined urban environments didn’t just lower urban temperatures, but were also beneficial for city dwellers’ emotional and physical health.

“You want to spend longer when you’re walking along a beautiful shady street,” she said.

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“It creates spaces where you want to linger and interact with other people, with a shopfront; a place where you might want to pause and have a seat; and none of those activities are much fun on a sweltering sidewalk with exhaust fumes that’s hot and dry and often dusty.”

The 3-30-300 concept was conceived by Dutch urban forestry expert Professor Cecil Konijnendijk in 2022, and is gaining momentum internationally in urban planning circles.

Konijnendijk said the benchmark was the “bare minimum” of what is required to cool cities and encourage active transport such as walking and cycling.

For Croeser, a complete rethink of the way cities are designed – and retrofitted – is required.

“Studies say we actually need at least 40 per cent canopy cover to substantially lower daytime air temperatures, so the ’30′ metric is the bare minimum – most buildings we studied don’t even reach that goal,” he said.

“If there’s an exciting call to action, it’s that our streets might need to look quite different in the future.”

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