When I grow up I want to live on a beautiful, lush, tree-lined street. Lots of us do.
We appreciate feeling close to nature, we love the symmetry and simple beauty of trees, and we crave the shade in the summer. What’s more, trees should earn the envy of any engineer – all at once, a tree is a solar energy converter, a rain interceptor and filter, an air filter, a home for multiple species, a shade structure, a wind shelter, a carbon sink, and a producer of food, oxygen and building materials.
I’d challenge you to find a local council or community vision for a city that didn’t include greener streets and neighbourhoods. More and more, we are realising the importance of trees in our cities, and urban forestry initiatives are rapidly inspiring and supporting the delivery of more trees. The recently published How to grow an urban forest puts forward a framework to support Australian councils in increasing their tree canopy cover.
But have you ever asked yourself where the trees would rather live, particularly as they mature? I’d bet it’s not in our streets, not in our city squares or even in our urban parks. For something that is so central to our vision of quality urban life and to the concept of liveability, it continues to surprise me that trees are so poorly integrated into the urban environment. We know we want more urban trees – but I bet the lush leafy vision you have in your head right now is not of a half-butchered, water-starved, dwindling carcass of a tree hopelessly straining out of a compact concrete casket in the street.
Before we push forward to make our dreams for increasing tree numbers in our cities, we have some serious work to do on the design front to make sure the integration of trees in the city fosters the kind of healthy trees we want and need. Here are a few core factors that require a fundamental rethink:
1. Design to provide trees with access to enough water
The serious impact that large urban trees in Melbourne suffered during the millennium drought is well documented. Some may not recover. Climate change will bring increasing intensity and length to dry periods, particularly in south-eastern Australia, and trees are a central part of the strategy to help humans cope with the climate – but will the trees survive?
We need designs which help trees access and store much more soil moisture to give them a fighting chance. At the moment, a standard street design is almost a sadistic mockery of the poor tree – wedged into a concrete balcony overlooking a stream of rainwater rushing along the curb beside it but unable to reach out and satisfy its thirst.
Passive watering techniques and integration with water sensitive urban design measures can help to provide water to trees while also taking advantage of the ability of soils and vegetation to filter and store water, benefiting our drainage systems and our waterways.
2. Design to provide trees with enough soil
Linked to the provision of water, but also to the provision of nutrients and structural stability, a tree needs sufficient soil volume. Fuelled by the need to neatly align planting within our standard street cross-sections, urban trees are often squeezed into tiny tree pits. Unsurprisingly, they aren’t becoming the large canopy wonders we want to see. The average lifespan of urban trees in America was found to be a meagre 13 years. We either need to rethink the space given to trees or we need to make the investment into load-bearing soil cavities that provide space underground while supporting trafficked surfaces aboveground.
3. Design to give trees fair rights
Often trees are seen to ‘clash’ with the conventional utilities within an urban environment, and when this clash occurs, the other utilities pull rank and the tree loses out – every time. Tree canopies are mercilessly cut back when they migrate anywhere near an overhead powerline – even when the tree was there first, the powerline is given precedence. Better planning of the air space is needed to ensure these two can both exist.
Similarly, underground utilities audaciously criss-cross under our streets and footpaths, meaning that finding even a single free spot for a new tree pit can be a challenge. Then should a tree root dare reach out in search of water, any skirmish with a pipe or heave of pavement is seen as a criminal offence (occasionally punishable by death). Better planning of the underground space would make urban greening a lot easier – imagine if utilities were orderly grouped in a shared trench? I’m sure the pipes and wires wouldn’t mind, we just need to convince their owners to work together.
Both above and below the ground, for some reason the humble tree is seen as a secondary utility, not the essential and much loved infrastructure we want for our cities. We need to elevate its status in both organisational mindsets and in urban design manuals.
Warwick Savvas, a landscape architect at ASPECT Studios, is working to better integrate trees in the urban environment and sees hope for changing practices in cities in the future:
“I think that the cities of the future will be better equipped to support living systems,” Savvas said.
“Extending Le Corbusier’s famous quote, ‘a city is a machine for living in,’ then trees and other living systems – what I call green infrastructure – are integral to the machine and need to be given the same consideration as the grey infrastructure of roads, pipes, and wires. With focus on good planning and design and recognition of the public benefits that come from greenery, I believe better integration will occur.”
So we power on toward our vision for green, leafy neighbourhoods. Though take heed Australia – a survey by the University of Tasmania tells us that Australia has the highest proportion of climate change sceptics in the world. Does this scepticism exist in the design community too? Will we realise that we not only desperately need more trees to keep our cities functional, but also that our current design paradigm for urban trees isn’t working? Let’s not create tree cemeteries in our streets bearing only memorials to the trees we wanted that died too young. Let’s plant more trees, but also design cities to care and support healthy, resilient trees – our most ingenious utility.