Why greening is important for public health

The ways in which urban greening can improve our health are numerous – including encouraging people to get out and walk or ride a bike. They are simply more likely to do so when the streets are shaded by trees, according to Link Place director and former Major Cities Unit director Sara Stace.

Stace says that when people use active travel, 80 per cent of the economic benefits for society are the reduction in health costs. These include reduced risk of cardiovascular problems, mental health issues and the likelihood of getting diabetes.

“All of that risk is less if people are exercising and getting outdoors and being active,” she says.

She says it is also well known that having good quality public space, including streetscapes with trees and planting, and parks that are accessible and feel safe is necessary to encourage people to be out on the streets.

As part of the new Adelaide Design Manual, creating more greening is one of the seven elements for improving the quality of the streets, says Daniel Bennet, Adelaide City Council’s program manager for city design and transport.

Bennett says there is currently only 30 per cent canopy cover on the city’s streets.

“There are bits missing in terms of greener, safer, cooler streets,” he says. This leads to anomalies like people driving to the park rather than walking there.

It’s not easy for the council to get trees in the ground on all its streets, because at least 90 per cent of them are impervious. So the manual includes other ways to add greenery, including green walls and roofs.

The goal is to activate street frontages, he says.

Council has a $1 million fund set up by former councillor and now Senator Robert Simms to kick-start the green roofs and walls trend and to start the conversation with private buildings.

The council itself is installing a green wall as a retrofit on its offices to show people what can be done.

Greening is about mental health and wellbeing, Bennett says.

“Sick people who have a view of landscape feel better, and heal faster. You just feel better looking at green.”

Bennet says policy should be showing the benefits of greening, and also explaining the “dis-benefits of not doing it”.

He says people are seeing the value of greening more and more. There are community groups calling for greening in the north west of the city, for example, where it is 10 degrees hotter on average in summer than the leafy suburbs.

Businesses are also seeing value in it. Council has a small grant scheme this financial year to co-fund up to $5000 in improvements to shopfronts. Bennett says a lot of applicants wanted to install green walls.

The health and wellbeing aspects of greening are central to the 202020 Vision’s plan for increasing green space by 20 per cent across the nation by 2020. And there is abundant research that backs this as a focus.

CSIRO researcher Dr Brenda Lin says that vegetation cover mitigates extremes in climate fluctuations, and also protects ecosystem processes and increases the resilience of communities to heat events.

She says the research report, Pathways to Climate Adapted and Healthy Low Income Housing, which shows the relationship between land surface temperature and vegetation across four cities, also highlights that “those members of our community that are the most vulnerable to heat-related health impacts, often live in some of the hottest parts of our cities – exacerbating risk”.

CSIRO researcher Dr Dong Chen has looked at the impact of greening in cities in terms of reducing heatwave mortality.

Research for Horticulture Innovation Australia published in 2013 looked at the urban scale, and what the impact of greening is on the local climate. The research team looked at 20 years of records for deaths and hospital admissions in Sydney, Brisbane and Melbourne.

Dr Chen says they then looked at the current climate, and potential future climate scenarios using climate change modelling for 2050 and 2090.

“We also modelled the CBD of Melbourne using different vegetation settings,” he says.

They looked at what would happen to temperatures if the current level of greening was replaced by leafy suburban streetscapes, and found it reduced maximum temperatures by 0.7 degrees Celsius, and reduced heatwave mortality by between five and eight per cent.

Replacing the current CBD vegetation landscape with grass and sparse forest-type vegetation cover reduced maximums by between 1.5°C and 2°C and mortality by nearly 30 per cent, and this reduction held true even if the climate got hotter.

“All three cities can increase their green coverage and reduce summer maximum temperatures,” Dr Chen says.