Trees

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.

A place for trees: the RJ Hamer Forest Arboretum

The model for a typical arboretum is a showcase of singular trees; example after example of what each species can accomplish, if grown with enough space and the right conditions. The Royal Botanic Gardens in Melbourne, for instance, have a section reserved for the many varieties of oak tree found across the world – a gentle lawn dotted with lush mature specimens, conveniently demonstrating quirks of leaf and bark and acorn.

On the north-eastern side of Mt Dandenong, a different sort of arboretum has been slowly establishing. During the 1960s, attention was given to a section of the Woori Yallock State Forest that had slowly deteriorated with the fire outbreaks of the early 20th Century. The loss of mature forest and overall habitat integrity meant that in the ‘40s and ‘50s the land was reallocated, to be used for pine plantations. Unfortunately, a pattern followed and these timbers were also destroyed by fire in the heavy blazes of the 1962 summer. It was at this point that the state government took notice, and Victoria’s program of transformation into The Garden State gained a new asset.

The lower entrance to the arboretum. Photo: Paul Jones

The lower entrance to the arboretum. Photo: Paul Jones

The RJ Hamer Forest Arboretum – named for the Victorian Premier who presided over its creation – uses densely repeated plantings to create mesocosms of woodlands from Europe, America and Asia. The main aim of the park was the planting of less flammable trees, as part of the fire plan to protect the nearby townships on the mountain. It currently holds approximately 200 species of plants and trees, a large number of them exotic and deciduous trees. A report in 2004 credited the forest park with a design unique amongst Victoria’s gardens.

The main entry to the park is not inviting; in fact, its lack of promise is almost an initiation test. A single unsealed track, sidling down off the Olinda-Monbulk Road amid overflowing verges, is marked by no more than a brief sign: “To arboretum.” Creeping between property fences and roadside trees, dust and the fear of potholes exaggerate the quite short distance to the park (in all honesty, the road itself is actually rather mild too).

Mature woodland extends all the way to the Chalet Road carpark, keeping hidden the first reward given to those who pass initiation – an astonishing view of the landscape, falling away in folds and curves across the Yarra Valley and sweeping up to the first foothills of the Great Dividing Range. The forested valley in the foreground is framed by an avenue of trees that echoes the formal plantings of grand estates. In the blue distance, mountains hide their peaks among cloud on all but the brightest days. 

European ash ( Fraxinus excelsior ). Photo: Paul Jones

European ash (Fraxinus excelsior). Photo: Paul Jones

The place is an actual wonderland, in a very Lewis Carroll kind of way. The collection falls across the sheltered valley in a haphazard quilt of treescapes, native and exotic patches mixed together with the foremost concern being merely how best to allow each species to grow unimpeded. Only a satellite view fully conveys the abruptly artificial arrangement.

From wandering among the ferny darkness and vertiginous columns of a Eucalyptus regnans forest – and with the mature individuals here, you can easily believe this species is the tallest flowering plant in the world – a single turn of the path takes you to mellow woodlands of birch, a displaced outpost of the lowland forests of Europe and America. Further on, a sunlit stand of European ash turns golden in the summer heat. Up in the higher reaches of the valley, stands of 40 year-old Sequoiadendron giganteum give a teasing hint of the heights they’ll reach in their second and third centuries – the species, the tallest of all plants and specimens of which rank as the largest single organisms on the planet, is labelled with hilarious accuracy as “Big Tree.” Less obvious to the unaware, a stand of Pseudotsuga menziesii is simply given its common name of Douglas Fir – no indication that this planting of American conifers has created a miniature forest of the classic American Christmas tree. Down near the picnic ground toward the valley floor, a patch of Liquidambar formosana bides its time until autumn brings out a dazzling bonfire of colours. Estimates from the Parks Victoria management team place each habitat at around a half-hectare in area, giving a visitor the chance to bury themselves completely in an environment before darting on to the next.

Groundcover of daisies,  Plantago  ,   P. vulgaris  and bracken. Photo: Paul Jones

Groundcover of daisies, PlantagoP. vulgaris and bracken. Photo: Paul Jones

The profusion of plants from the Northern Hemisphere might seem a potential concern for the nearby native forests, as the surrounding hills bear numerous cases of garden escapes and weedy colonisers. Even in the park itself, a sharp-eyed walker might spot amongst the undergrowth carpets of wild strawberries, long-leafed plantain, and the jolly purple spikes of Prunella vulgaris. Elsewhere is the less welcome purple of scotch thistle flowers, inescapable anywhere with an agricultural past.

But a scan of the management plan for the arboretum shows just the opposite problem – thriving natives are invading the exotic patches, disrupting intentions to the extent that they need to be removed. The park poses no real threat to Mt Dandenong’s iconic mountain ash forests, and brightens the area with its incongruous collection.

While our slogans have moved with the times, Victoria is still very much a garden state. These parks and forests are a central part of our identity, and our safeguard against forgetting our place in the environment. For Melbourne, the RJ Hamer Arboretum with its woodlands is a particular treasure.


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.