By Jordan Baker
One in seven Sydney suburbs is in dire need of more tree canopy cover, and the lack of heat-mitigating shade is worst in the city’s poorest areas and in the new estates where nature has been razed for development.
The places with the least canopy cover – which include Fairfield, Merrylands and newer parts of the Hills – are up to 10 degrees hotter than heavily vegetated areas, figures from the NSW Department of Planning show.
The data comes as a heat catastrophe smothers the northern hemisphere; Europe and Japan face record temperatures, the United States swelters, and smoke from wildfires in Canada infects the air breathed by 70 million people.
Academics say Sydney is failing to factor rising temperatures and climate change into its development policies, and warn that a lack of trees and green space will not only fail to protect against heat, but lead to poorer social and health outcomes.
The department’s report details the level of tree canopy coverage across more than 750 suburbs. One in seven has between zero and 10 per cent of its area covered by tree canopy, which the department considers “very low”.
Almost 30 per cent – including Burwood, Ultimo and Five Dock – have just 10 to 20 per cent cover, which is well short of the desired 40 per cent or more.
Experts say there is not enough room left for heat-mitigating trees in Sydney’s new suburbs, like Marsden Park.Credit: Nearmap
The suburbs considered by the department to be most vulnerable to the adverse effects of urban heat are clustered in the inner south-west, and include Campsie, Belmore (both slated for intensive development) and Cabramatta.
The department also estimated how temperatures in different areas were inflated by the urban heat island effect, which is based on how the temperature of those suburbs deviates from heavily wooded areas or national parks.
It identified 175 suburbs that were eight or nine degrees hotter than vegetated suburbs. One, the outer-south west suburb of Carnes Hill, blew out by 10 degrees. Only a handful, such as Berambing and Linden in the Blue Mountains, were cooler.
Sebastian Pfautsch, an associate professor in urban planning at Western Sydney University, said new estates on the fringes – where most developers cut down the existing trees before they began to build – were failing to plan for enough natural shade.
Modelling suggested that even when trees along new verges grew, there would only be about 26 per cent cover, which was not enough to mitigate the effects of intense heat.
“When you think about it, Marsden Park, The Ponds, Kellyville, Box Hill – everything you see coming up in the north-western growth centre, that’s in the hottest part of the western Sydney basin,” he said. “That’s where they’re putting hundreds of thousands of people, knowing that in the future they will have no shade. It’s a disaster in the making.”
Urbanised areas with little tree cover tend to have had an industrial history, with big turning circles, car parks and warehouses. But Pfautsch said development in those suburbs was also failing to ensure open space was expanded or protected.
“The process of densification most likely is at the cost of open space,” he said. “It’s way too expensive for local government to buy back land to put green space into densifying suburbs.”
Minister for the Environment and Water Tanya Plibersek and Minister for Employment and Workplace Relations and Minister for the Arts Tony Burke announce federal funding for the Cooks River.Credit: Rhett Wyman
Green space was also vital for community health, said Thomas Astell-Burt, a professor of public health at the University of Wollongong. Those who lived in leafy suburbs such as Mosman had far less diabetes, for example, than those in Blacktown.
“If you were to take a suburb with less than 10 per cent canopy, and increase it to a level of 30 per cent, what you end up with is a reduced risk of developing psychological distress by 31 per cent, [and] a 33 per cent reduction in the odds of a decline in general health,” he said.
“We need to have more equity of access to tree canopy cover. That’s partly because of the mental and physical health benefits.”
A NSW Department of Planning spokesperson said a greening program – involving $35 million in grants to councils to plant 107,000 trees over four years – aimed to increase green cover across Greater Sydney and lift urban canopy coverage to 40 per cent by 2036.
Even when buying back land for green space is too expensive, governments can improve the quality of existing parks. Last week, federal Environment Minister Tanya Plibersek announced $10 million for the rejuvenation of the degraded Cooks River, which flows through the once-heavily industrialised suburbs of Sydney’s south-west.
About $7 million of that will go to the establishment of a wetland along the concrete-lined river at Parry Park in Lakemba, a suburb with just 10 to 20 per cent tree canopy, the highest possible heat vulnerability rating, and a so-called urban heat island temperature boost of eight degrees.
Andrew Thomas from the Cooks River Alliance said Lakemba had very little natural space. “This will have a direct health benefit for people who live in that area,” he said. The money will also go to a new kayak launch spot in the Bayside area, and a rubbish collection trap.
Get to the heart of what’s happening with climate change and the environment. Our fortnightly Environment newsletter brings you the news, the issues and the solutions. Sign up here.