Recent research from Western Sydney University reveals how the presence or absence of trees can impact temperatures at the ground level in urban environments.
The study led by Dr Sebastian Pfautsch, a senior research fellow at the university, analysed temperatures at various locations in Parramatta, Cumberland and Campbelltown last summer. Two streets in Parramatta – located a kilometre apart – showed a perceptible difference in temperature during the heatwave.
Daking Street registered as the hottest street in the City of Parramatta's municipality with residents experiencing 13 days of 40°C or higher temperatures. Galloway Street, on the other hand, had a relatively milder microclimate with the area having just five days of temperatures above 40 degrees.
The study attributed the temperature difference between the two neighbouring areas to their tree canopy. With 10 percent tree coverage and greater exposed bitumen, Daking Street experienced sweltering heat for a longer period. Galloway Street’s tree canopy covers about 30 percent of the area, helping reduce the heat from the sun hitting the ground.
The study, which covered several suburbs in Sydney, revealed that some areas actually experienced higher heat levels than what the Bureau of Meteorology recorded.
Pfautsch’s research underlines the importance of tree canopies in urban ecosystems and how they can impact the microclimate of each area; greater tree coverage, for instance, can create 10-degree temperature differences, increasing comfort levels even during extreme summer heatwaves. Without a tree canopy, the heat from the sun directly hits the ground and gets trapped; it is subsequently released into the atmosphere, increasing the temperature.
Pfautsch has called for legislation that would require every house to plant two trees outside to mitigate the heat. The research also blames construction for the increasing urban temperatures.
City of Parramatta Council Lord Mayor Bob Dwyer has reiterated their commitment to NSW Government’s plans to plant five million trees across Sydney by 2030, a move that’s expected to take the city’s tree canopy from the current 16.8 percent to 40 percent.