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The solution to reducing extreme heat by up to 6 degrees is right in our own backyard
Aug
Australia has just experienced the second warmest summer on recordWith 2019 was the hottest year. Summer temperatures have soared across the country, causing huge economic and human losses. The good news is that we can do something about it in our own backyards. We’ve found that trees and vegetation can lower local land temperatures by as much as 5-6°C on days of extreme heat.
Our newly published research in Adelaide’s summer heatwave suggests that a straightforward solution to the extreme heat is literally within reach. It involves trees, grasses and vegetation in our own backyards.
Read more: Out in the heat: why poorer suburbs are at greater risk in warming cities
What did the research show?
During the three-day heatwave that hit Adelaide in 2017, AdaptationWest took to the air to measure land surface temperatures from a plane. Our analysis of data collected that day suggests that urban trees and grasses can lower daytime land temperatures by as much as 5-6°C during extreme heat.
Ossola et al., 2020. https://doi.org/10.25949/5df2ef1637124
The biggest drops in temperature were in the hottest suburbs and those furthest from the coast. These significant drops were achieved largely by trees in backyards.
The benefit that urban trees provide therefore has two key aspects:
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maximum cooling occurs when needed most – on days of unbearable heat.
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maximum cooling occurs where it is needed most – close to us, people, in the communities in which we live.
Our analysis also shows that the modest home garden is more than adequate when it comes to reducing extreme urban heat and its harmful effects. Although yards and gardens only occupy about 20% of the urban areathese private spaces provide more than 40% of the area covered with trees and 30% of the area covered with grass in Western Adelaide. This is comparable to what you would find in many other Australian cities and towns.
AdaptWest and Airborne Research Australia
In fact, the range of tree crowns in private parks is much larger than in typical city parks or public green areasThis means these private green spaces are an crucial, yet often overlooked, way to combat extreme heat.
Read more: Our land is opulent in green belts – we can definitely do more than just mow one third of the city’s greenery
Planning for climate-ready cities
Climate models and forecasts predict that extreme heatwaves and heatwaves will become more regular and intense. Penrith reached 48.9°C on January 4 this year, making Western Sydney the hottest place on Earth that dayConsidering that heat waves are already occurring, considered to be the most tragic climate disaster in Australiapredicted temperatures pose a earnest threat to human life.
Meteorological Office, Legal disclaimers
Urban planning increasingly has to take extreme temperatures into account. For example, the City of Sydney recently announced an ambitious policy to boost by 2050, the area of green areas in cities will increase to 40% for resilience to climate change. Currently, this level of green cover is only found in a handful of suburbs in cities like Melbourne, Sydney and Adelaide.
Read more: How to protect ageing Australians from the heat? Greening our cities is a good start
To achieve such ambitious and life-sustaining goals, our results point to the need to preserve, protect and enhance urban greenery in our own backyards. As our cities become denser, trees and people’s backyards can play an invaluable role in climate change adaptation.
Most council, state and federal policies to date have neglected backyards and trees when thinking about climate change adaptation. As we imagine how Australian cities should grow, develop and thrive, more attention needs to be paid to the spaces where our backyards and trees can assist reduce the devastating impacts of climate change on people and communities on our doorsteps.
Climate change is causing a social, cultural and political revolution. It requires bold, decisive and immediate action. This is a once-in-a-lifetime opportunity for intelligent and proactive planning, policymaking and community action. This work must begin now.
However, urban forests do not grow quickly. We need to encourage the employ of low-water grasses and shrubs as a quick transition strategy for urban cooling.
This is a momentary solution until a huge army of climate-ready tree soldiers emerges, which we can start planting today, and which will take over the task of combating climate change and extreme heat in our future cities.
Read more: Our cities need more trees, but some commonly planted won’t survive climate change
For more information and news, please visit Smart Green Cities Macquarie University AND AdaptWest in Adelaide.
