Urban growth: the plan for a forest metropolis

Artificial: it’s a word that comes loaded with meaning. When we call things artificial – colours, flavours, flowers – we’re often saying, just quietly, that it’s not as good as the real thing. To be artificial is a substitute, a compromise. It’s a lot of weight to bear for a term that originally described something simply as human-made, rather than naturally occurring.

In the category of artificial landscapes, a modern city is about as brazen a creation as is possible to find. The office buildings amassing to form mirror-sided canyons; the precisely parallel layouts of street, gutter, footpath and riverside; often softened only by plantings of identical trees, with a single species marching along streets in cookie-cutter repetition. It will surprise very few people that in Melbourne’s CBD, the distinctive London Plane trees account for 75% of the existing timber (interestingly, our plane trees are themselves most likely a human-made species – a hybrid of Eurasian and American parents).

Image: Visit Victoria

Image: Visit Victoria

In 2012, the Melbourne City Council began developing a plan that would change the face of the city, with a raft of environmental, cultural and economic benefits. The Urban Forest Strategy sets six targets for the city; primarily aimed at tree canopy density, diversity and health, it also focuses on water, soil, and changes to urban planning that involve the community and ensure ongoing function.

As a social need, the inclusion of green spaces in urban planning has been long established. The Urban Forest Strategy draws attention to a statement made by Melbourne’s emerging Town Council in 1839: ‘It is of vital importance to the health of the inhabitants that there should be parks within a distance of the town.’ In Europe during the same century, a similar shift was seeing the development of gardens for public use instead of the more cloistered spaces owned and policed by the very rich. Social observers were seeing that the Industrial Revolution, leading people away from rural environments to the dense labour markets of cities, had also brought about many mental and physical health issues. Neuroscience research in recent years has supported this, finding that spending time in a natural environment reduces activity in parts of the brain associated with mental illness.

The benefits of urban trees. Source: City of Melbourne Urban Forest Strategy

The benefits of urban trees. Source: City of Melbourne Urban Forest Strategy

In modern Melbourne, incorporating trees into the central streetscape as well as our parks has brought with it additional advantages. Urban trees provide natural shade, detectably lowering temperatures on footpaths; they sequester carbon, offsetting urban emissions; they have been found to reduce nitrogen dioxide, a component of urban pollution linked to respiratory disease. This all translates into economic gains – tree-lined streets see a higher amount of pedestrians, generating more passersby for local shops.

When it comes to revegetation programs, one of the most admirable components is restoration. The Australian landscape has been drastically changed since the arrival of Europeans, with the greatest shifts occurring in the oldest colonies and capital cities – recent research has been at pains to discover what the land looked like before settlement began. Nevertheless, this research has helped create rehabilitation programs in the Benalla region, throughout Gippsland and the Yarra Ranges, and other places around Australia, often giving wonderful results. In these locations, returning the countryside to its pre-industrialised condition has seen the return of threatened birds and mammals, with remnant pockets beginning to thrive.

For cities, the reality is unfortunately different. Infrastructure and landscape changes make it almost impossible to return the land to its pre-colonised condition, while dense populations with diverse requirements mean we can’t leave things untouched like we can in our National Parks. In order to maintain quality of life for all residents, intervention and reshaping is a necessary process. But for Melbourne’s urban forest, this doesn’t have to be a problem.

Urban trees provide habitat for apex predators like the powerful owl. Image: CSIRO

Urban trees provide habitat for apex predators like the powerful owl. Image: CSIRO

Before Europeans arrived, the landscape at the mouths of the Yarra and Maribyrnong was a gentle, open grassland with denser woods only around the rivers – even then, the rising salt from the bay meant that few tree species could thrive close to the coast. Restoring this landscape around the infrastructure of Melbourne would allow a return of endemic ecosystems, but it would not be sufficient to achieve the necessary goals of cooling and shading Melbourne’s streets. The current vegetation, although limited by a lack of diversity and native flora, is quite likely to be the most densely forested this landscape has ever been.

In addressing diversity, the Urban Forest Strategy has set an ambitious target with the 5-10-20 plan. At the strategy’s completion, Melbourne’s vegetation will feature single species to only a maximum of 5%, a single genus to 10%, and a single family to 20%. It’s wonderful to imagine – at least 20 different tree species will be present in our streetscapes, competing for our attention with changing shape and colour. The plan also makes sense from a biological angle; the climate is varying in greater degrees of temperature and water availability, while pathogens like myrtle rust and cinnamon fungus are appearing in outbreaks throughout Australia. Myrtle rust has been detected around Melbourne in plant nurseries, and has so far been found to affect 350 native species from the Myrtaceae family – in the event of a future outbreak, the risk of losing only 20% of our cover is a much less severe possibility than losing the majority.

Embracing the chance to truly design our landscape and shape Melbourne for the future has the potential to create a beautiful and strong home for ourselves. Long-term planning and informed decisions can protect us from changing conditions, whilst leaving behind limitations of conventional ideas opens amazing possibilities in architecture and vegetation.

A city is always artificial. But it can also be a place of artistry.


Paul Jones

Paul works in science education and has been a teaching member of Monash University's Department of Biology since 2010. He is interested in community engagement and sustainable urban development.