On average, someone is hospitalised for a heart attack every 9 minutes, according to the National Heart Foundation of Australia. And the toll on taxpayers runs into billions each year.
Reduced cardiovascular disease
Few studies have explored whether health benefits from urban greening translate into reduced healthcare expenditure. Study co-lead Professor Xiaoqi Feng from the University of New South Wales and her team sought to answer this question.
Using a longitudinal cohort study (the Sax Institute’s 45 and Up Study), they tracked cardiovascular events and mortality over 10 years by linking health data from more than 100,000 Australian adults living in apartments or houses in Sydney, Newcastle, or Wollongong. Factoring in tree canopy cover and open grass within 1.6km buffers, the study found urban green space, particularly trees, can reduce the risk of cardiovascular disease.
Raising the tree canopy cover from 10 to 30 per cent could therefore save between $193 and $569 per person annually.
Professor Feng asks: if having more tree canopy nearby helps to keep people out of hospitals, how much more money is saved from all the medications and therapies that are avoided when people don’t get heart disease?
So, how does urban greening help reduce cardiovascular disease?
Professor Feng notes that previous studies suggest three possible ways:
First, urban greening promotes increased physical activity, social connectedness, and better-quality sleep. Second, people living closer to nature are more resilient to chronic stress and finally, a generous tree canopy affords better protection from heatwaves and air pollution.
Yet, Professor Feng says, many planners and developers—and even healthcare professionals—give low priority to considering urban green space as a health resource.
“More research on the type and quality of green space is needed, but we hope this evidence will encourage planners and health professionals to champion existing and new greening strategies, particularly given the increased rate of urbanisation worldwide,” she says.
Lower dementia risk
Living near an urban tree canopy is also associated with a lower dementia risk.
An estimated 433,000 Australians live with dementia, a number projected to more than double by 2058. In a world-first, Professor Feng worked with Professor Thomas Astell-Burt and Dr Michael Navakatikyan to examine dementia diagnoses among participants in the Sax Institute’s 45 and Up Study. Using hospital admission data and mortality records from more than 100,000 NSW-based adults, they reviewed cases of dementia over 11 years.
Consistent with expectations, the study found that living in an area with more than 20% tree canopy lowered the risk of developing dementia by 14% over 11 years. Increased physical activity, lower psychological distress, higher social support, and decreased incidence of diabetes all partially mediated this risk.
Professor Astell-Burt, Director of Flourishing Cities at the University of Sydney, said we reap what we sow.
“These findings clearly indicate, if we look after the natural environment, it will sustain us in a myriad of ways,” he says. “If we chop it down, we are chopping ourselves down. We must protect it to protect ourselves – we are nature.”
Mitigating heatwaves
Heatwaves kill more Australians than any other natural disaster, including bushfires, cyclones and floods. As global temperatures climb, urban greening offers a crucial defence against the health risks posed by urban heat islands.
A recent collaboration between the Population Health Research Network (PHRN), the Australian Urban Research Infrastructure Network (AURIN), the Australian Research Data Commons (ARDC) and researchers from QUT, UWA and RMIT culminated in a suite of new Australian Urban Health Indicators. These tools will help researchers better understand how the built environment influences human health. Urban planners and policymakers can use these data assets to strengthen health and social infrastructure planning in both urban and regional areas.
Investing in urban forests, our living infrastructure, will help ensure cooler, healthier, and more resilient communities for generations to come.
More information
Astell-Burt T, Navakatikyan M, Feng X (2023). Why might urban tree canopy reduce dementia risk? A causal mediation analysis of 109,688 adults with 11 years of hospital and mortality records, Health & Place, Volume 82. Read article
Feng X, Navakatikyan MA, Toms R, & Astell-Burt T (2023). Leafier communities, healthier hearts: an Australian cohort study of 104,725 adults tracking cardiovascular events and mortality across 10 years of linked health data. Heart, Lung and Circulation, 32(1), 105-113. Read article
Feng X, Navakatikyan M, Eckermann S, Astell-Burt T (2024), Show me the money! Associations between tree canopy and hospital costs in cities for cardiovascular disease events in a longitudinal cohort study of 110,134 participants, Environment International, Volume 185. Read article
