Can planting trees every 10 metres help us beat the heat?

Daniel Bennett Daniel Bennett
Integrated Design Practice Leader – SA
Heath Gledhill Heath Gledhill
Integrated Design & Precincts Capability Leader, Australia & New Zealand
13 October 2021
6 min read

The world is getting too hot to handle.

In June 2020, the City of Miami in the United States announced the appointment of its first ever Chief Heat Officer – a big first for the municipal government and in the world. The introduction of the new role was designed to raise awareness about the impact of heat on human health and economies and do something to combat it.

According to a recent report by the United Nation’s Intergovernmental Panel on Climate Change (IPCC), severe heatwaves that used to occur once every 50 years will likely happen once per decade. This was supported by Nature Climate Change journal’s study which predicts that record-shattering heat events will probably happen seven times between now and 2050, and 21 more times between 2051 to 2080.

The world simply can’t (or won’t be able to) handle the heat anymore – unless we do something about it. But while the growth of renewables and other technologies contributing to a sustainable future continues to accelerate, recent research reveals that we’ve been overlooking one of the most effective climate change solutions that’s available to us right now: trees.

A single healthy tree, in fact, can have the cooling power of 10 air conditioners. They absorb carbon dioxide, reduce floods, boost biodiversity, filter air pollution, and improve public health, among many other benefits.

If ecologists say that a bee should never be more than 20 metres away from a plant, what if we made the same rules about trees and humans? Just imagine, if we plant a tree every 10 metres and recommend that no human should be further away from a shade tree for more than that long. What would that look and feel like?

Our trees are dying: care begets care

The IPCC noted that if we wanted to minimise the rise of temperature to 1.5 degrees Celsius by 2050, we need an extra 1 billion hectares of trees. However, it won’t merely require planting new trees, it will also require us to maintain and take care of the older and more mature trees in our habitat.

As the world gets warmer and warmer due to climate change, the longevity of trees in forests is being reduced. Trees are dying very young, unable to reach their full potential. For forests and trees to protect us, humans must protect them first and secondly sustain them.

Researchers from the University of Melbourne and University of Queensland found that while rising temperatures pose a risk to our forests and trees, there are several strategies we can adopt to address this. And, aside from these strategies, their study found that new tree species can be introduced to our cities that can adapt to future climates and potentially provide a wide range of advantages.

This is good news for urban areas where city dwellers are experiencing the ‘urban heat island effect’ – a phenomenon that causes cities to retain more heat because of heat-absorbing surfaces like concrete, car parks and buildings.

Imagine if we are able to adapt this to our street trees – growing healthy and leafy trees 10 metres apart for years to come. How much cooler would our cities be? 

Can trees make us better people?

It may be hard to imagine how a plant or a tree – which stands still in its place for its entire lifetime – helps bring balance in our ecosystem and health to humans, but they do. Research has revealed how salutogenic design and exposure to nature help people heal and recover quickly from illness, and ultimately become healthier.

Recently, a study in Germany found that “living within 100 metres of a tree can be enough to reduce the need for antidepressant drugs”. Participants who spent time in leafy environments, felt less anxiety and stress, and showed lower levels of the biochemical stress indicator serum cortisol. Trees can make us happy.

And research shows that trees can make our cities safer to live in. In a fascinating report from Baltimore, it was revealed that a 10 per cent increase in trees resulted in a 12 per cent reduction in crime. And in another US State, there was a 14 per cent decrease in property crimes and a 15 per cent reduction in violent crimes.

Just imagine cities and communities that are safer, healthier, and happier. That would be priceless.

Not all trees are created equal

When it comes to fighting climate change, we might be in the same storm, but we’re not all in the same boat. Unfortunately, even when it comes to trees, equity is also an issue.

People living in low-income neighbourhoods often get fewer trees compared to upscale villages. A National Public Radio analysis of 97 of the most populous cities in the US found this to be true. The percentage of trees in low-income areas was starkly different to well-off neighbourhoods.

The City of Onkaparinga, south of Adelaide, Australia has taken up the challenge of prioritising areas of social and economic disadvantage for new street planting – with a strategy called the Suburb Improvement Program (SIP) as part of Greening Onkaparinga.

The strategy outlines a detailed assessment of tree canopy cover, urban heat island mapping, and social vulnerability, which supports more disadvantaged people within their community and prioritises tree planting renewal and replacement.

The city has planted approximately 10 000 new trees over the past decade and is programmed to continue the delivery of 1000 new street trees and streetscape improvements every year, encouraging more residents to walk through their suburbs more often.

Setting our priorities

Despite the many advantages, there are many critics who say trees interfere with our underground and overhead infrastructures, but where does the balance lie? That is the question, which design professionals are now challenged with and must come together to develop an integrated and beneficial solution.

Trees are often seen and treated as an amenity or accessory to what we design and build, but if we look at it more deeply – to its roots (pun intended) – we’ll realise they’re more than that. Trees are critical infrastructure that impact humans’ lives and survival. Accordingly, they should be given the same level of importance. We call it ‘urban green infrastructure’.

We have the capability, opportunity, and technologies at hand, and our challenge is how we reset our priorities and make urban green infrastructure as important as reliable WiFi or power supply. We must adapt.

There’s a Chinese proverb that says “The best time to plant a tree was 20 years ago. The second-best time is now.” The heat is literally and figuratively breathing down our necks. The pressure is on. Can we handle it?

Click here to subscribe to Just Imagine.

Daniel Bennett
Written by
Daniel Bennett

Daniel is at home in the lower Adelaide Hills with his young family, restoring the Greybox Woodland on his property, and savouring the Hill’s amazing cooler climate vinos.

Heath Gledhill
Written by
Heath Gledhill

Focusing on pioneering a new way of thinking within an engineering focused firm, bring people, community and the environment to the forefront of the conversation.

Unfortunately, you are using a web browser that Aurecon does not support.

Please change your browser to one of the options below to improve your experience.

Supported browsers: