If the term “urban heat island” wasn’t bad enough, experts have now coined the phrase “urban heat continent”, highlighting the spread of heat affected urban areas in Australian cities, primarily Melbourne and Sydney.
A recent survey by 202020 Vision gathered information from local government areas (LGAs) to assess their total number of hot days, the ability of the local population to remain healthy in the heat, and the amount of green space present.
Not surprisingly, acreage of green space is directly related to an area’s ability to deal with heat. Critically, green spaces dramatically cool immediate surroundings (see thermal diagrams of Parramatta tree-lined and unlined streets below), but as an added bonus, also have a direct impact on people’s well-being and overall happiness. In the last four years, canopy coverage has declined 2.1% nationally, the equivalent of 162,000 MCGs.
According to the survey, nine local government areas were found to be Australia’s most vulnerable to heat stress:
- Hume, Darebin and the city of Ballarat in Victoria
- Gawler, Port Adelaide Enfield, West Torrens, Playford and Charles Sturt in South Australia and
- Belmont in Perth.
Large chunks of Sydney only just escaped being in the most heat-vulnerable category. Rockdale, Holroyd, Canterbury, Botany Bay and Blacktown all scored poorly for heat stress.
Launceston was the most heat-vulnerable council in Tasmania. Logan, Ipswich and Toowoomba took out the dubious honours in Queensland.
Generally speaking, poorer suburbs are the most affected by heat waves, while wealthier suburbs stay cooler because of more greenery and parks. In outer suburbs, houses are often built on smaller lots, meaning smaller gardens and more concrete and aggregate, which absorb heat and then releases it back into the atmosphere.
So what can councils do to combat heat waves in urban areas? There are many great initiatives underway.
Moreland Council in Melbourne’s inner north has put in place a specific Urban Heat Island Effect Action Plan that will see Council increase canopy cover, conserve water to keep spaces green throughout summer, encourage the use of cool roofs, shading, and insulation, and monitor technology of ‘cool roads’ so they can use better surfaces when possible.
WALGA (West Australian Local Government Association) has produced an Urban Street Trees discussion paper in order to formalise a policy on street trees in southwest WA and especially the Perth area. The comprehensive paper looks at everything from the definition of ‘street trees’, to urban heat island effects, liveable neighborhoods, mental health benefits, and many related topics in between.
On a national level, the Department of Industry, Innovation and Science published ‘Cool Cities: Guidelines for Optimised Tree Placement’ which helps councils not only understand the science behind advantageous tree plantings, but also provides guidance on large scale landscaping and tree arrangement.
Aside from helping to reduce temperatures, trees do far more for us. As mentioned before, they cheer us up! Academics at the universities of Melbourne and Tasmania examined 2.2 million messages on Twitter and found that tweets made from parks contained more positive content – and less negativity – than tweets coming from built-up areas. This opinion piece in the Sydney Morning Herald by economics editor Ross Gittins, elaborates on why we must give trees a chance in this increasingly urbanised world.