Researchers from the Institute for Sustainable Futures have produced the first national data on urban tree cover, helping us understand why certain urban areas are much hotter than others, and more importantly, what we can do about it.
Institute for Sustainable Futures
Building Resilience for Climate Change Fund (NSW Environmental Trust)
NSW Adaptation Research Hub (NSW Office of Environment and Heritage)
Penrith City Council
It’s a searing summer day in Sydney’s CBD, but in Penrith and other outer western suburbs not reached by the cooling sea breeze, the temperature is climbing a scorching 10 degrees higher.
In 2014, the Institute for Sustainable Futures's Research Director Dr Brent Jacobs and Research Consultant Candice Delaney, produced the first national data on urban tree cover that is now contributing to our understanding of why these areas are so much hotter and what we can do about it.
In a project commissioned by the Nursery and Garden Industry Association and 202020 Vision (an organisation dedicated to getting 20 per cent more tree cover by 2020), Jacobs and his research team created heat maps of the 139 most urban Local Government Areas (LGAs) in Australia.
Starting with Google Earth images, the researchers superimposed i-Tree software — designed by the US Department of Agriculture Forest Service — over all 139 areas to assess the tree, shrub and grass coverage of all those suburbs.
“While our capital cities are not really in comparable environments, within each city we found some very diverse tree cover,” Jacobs says. For example, Hobart had more than 59 per cent tree cover while Sydney CBD only had 15 per cent, but within Greater Sydney, suburbs such as Hornsby and Pittwater had 59 per cent tree cover while most western suburbs had less than 20 per cent.
“We saw a lot of intense heat particularly on big roads like Parramatta Road, Victoria Road and the Great Western Highway,” says Jacobs.
As a result of this Where Are All the Trees report, Penrith and Leichhardt Councils commissioned Jacob’s team to conduct specific research on their LGAs, using i-Tree and CSIRO heat maps to zone in on the worst-affected urban heat islands. The team also visited the sites to take actual heat readings in the summer of 2014–2015.
“It was very simple and powerful but especially in Western Sydney, we were able to make the close association that high-density housing developments had cleared land and lacked tree cover, and dark roads were corridors where heat just couldn’t escape,” Jacobs says.
His research also made the strong connection that disadvantaged, disabled and elderly people were worst affected by these heat islands.
“They have to live in these high density areas and have to rely on public transport on main roads,” he says. “They don’t have the financial resources to make changes to their lives and the NGOs and councils we interviewed hadn’t previously taken heat into their consideration as a trigger for assistance.”
But the councils now have his reports and are taking his recommendations on board. “Leichhardt Council approved a whole raft of resolutions to address urban heat, which is pleasing,” says Jacobs.
“Penrith is using our research in its ‘Cooling the City Strategy’ with initiatives such as planting 4000 new trees in Leonay and Emu Plains, adding water features to school design and using light-coloured building materials.”
While the council reports are still in the publication process, this has already led to another project — Climate Adapted People Shelters — where Jacobs is working with Penrith, Parramatta, Canterbury and Ashfield Councils to design more environmentally-friendly bus shelters.
Photo supplied by Brent Jacobs