What happens when we cut down trees for car parks? Eastern Melbourne is finding out

Chadstone resident Paul Hepper once loved living near the mature London plane trees along his nature strip, providing canopy protection to the street and nearby houses.

But after the local council ripped the trees out to widen the road for extra parking spaces, cover from the heat can be hard to come by. It’s a pattern being seen across the eastern suburbs. 

Hepper told the Eastern Melburnian a lot of redevelopment across Melbourne’s eastern suburbs “takes up the whole block”, leaving “no room for canopy trees”.

“These McMansions are heat pits and an example of going in the wrong direction,” he said.

🌳 What to do about tree loss in our cities? As the development of the eastern suburbs of Melbourne continues to lead to mature tree removal and mid to high-rise buildings, how should communities incorporate more greenery into our grey developments?

☀️Health risks rising: According to the first ever National Climate Risk Assessment report released last week, we currently experience four days of extreme heat - where the average Australian temperature is in the top one percent of records - a year. The report found this would increase to 18 days per year under a 3°C warming scenario.

Global warming is currently confirmed at 1.2ºC above the pre-industrial average temperature from the late 1800s. However, warming across Australia has already reached 1.5ºC.

A 2024 United Nations report estimated global warming will reach 3°C by 2100 if governments do not take more severe measures to reduce pollution.

Once the global warming level exceeds 3°C, heat-related mortality is projected to increase by 259 percent in Melbourne, 444 percent in Sydney and 423 percent in Darwin.

🏠 Innovative infrastructure: According to Professor Stephen Livesley from the University of Melbourne School of Agriculture, Food and Ecosystem Sciences, part of the solution will be thinking of more creative ways to integrate resilient vegetation into design plans.

“If you just put plants in the ground that you've compacted and degraded through the construction process, those trees will not be very healthy and not grow very well,” he told the Eastern Melburnian.

Livesley said creative technologies could include soil vaults, where an underground plastic system can be built into concrete and asphalt infrastructure to house an uncompacted volume of soil and nutrients for urban trees.

“It just costs a little more, but what you will end up with - in 10, 20, 30 years’ time - is a very healthy and vibrant vegetation planting in a very dense area,” he said.

💰Cost vs value: University of Melbourne lecturer in urban greening, Marie Dade, told the Eastern Melburnian there is often a “mismatch” of priorities, with governments and developers building urban green spaces as cheaply as possible at the expense of “not really thinking about what trees are going to be best for supporting urban cooling”.

🥵 Absorbing heat with trees: Urban construction materials have a high thermal mass, meaning they can absorb a lot of heat. The air in urban areas can be eight to 10 degrees hotter than rural areas.

When the sun's rays hit the earth’s surface, they do not simply dissipate, but are absorbed into the surface.

If the sun's rays hit the tree canopy before hitting our urban infrastructure, however, that energy goes towards photosynthesis, and less heat is absorbed into the atmosphere. 

A small amount of additional cooling is also produced through the process of transpiration. This is when plants release water back into the atmosphere as vapour.

🖼️ The big picture: National advocacy organisation Sweltering Cities executive director, Emma Bacon, said while the recent release of climate-focused documents is a “really important” step, she and her team still hope it would lead to “more solid” regulations.

In terms of specific regulations, a number of the Federal Government’s plans, including the National Adaptation Plan and the Built Environment Sector Plan lay out the framework for expanding on current programs and delivering new rules to state and national building codes.

However, Bacon said “it's hard to say that it meets the moment in terms of the funding that we might like to see” towards these proposed plans.

Image Credit: David Hannah/City of Melbourne