‘Melbourne’s 2009 Heat wave saw more fatalities in one western local council area than those attributed to the bushfires on Black Saturday.’

Anecdotes which resound with a diverse audience can be powerful and become part of our oral story telling tradition. I’ve heard this anecdote about the 2009 heatwaves from multiple sources. The first time, it was presented by an urban designer arguing for more trees to reduce urban heat island effect. The last four times has been from civil engineers, design managers, traffic engineers and even project managers. On one project it was a turning point for a team to move away from the default position of ‘trees won’t fit in this project’ to, ‘we’ll make them fit’ and even in some cases ‘let’s start with the trees’. But this is not the norm. We still have a long way to go.

A target of 30 percent canopy tree coverage is commonly listed across organisations as a minimum target. So how are we performing? Metropolitan Melbourne has an overall tree coverage of 15.3 percent[i]. This varies from a high of 25.9 percent in average for the Eastern Municipalities to a low of 5.5 percent for those in the west. At the extremes, Yarra Ranges achieves approximately 36 percent and Melton only 4 percent. Granted, environmental factors such as topography, geology, microclimate and soil types all contribute to this difference. However, most of impact comes from the building of infrastructure and green field developments without a coordinated effort or contractual obligation to improve canopy tree coverage.

This is not for lack of trying. Numerous urban greening policies and plans have been released to target this issue. These range from State Government Department policies to local council strategic plans, to action plans from asset owners and private developers. Successful initiatives such as Greening the West have elevated the cause and delivered award winning results. But we still see an underperformance on numerous large-scale projects. The messages and anecdotes that accompany them need to continue to be shared.

Governance of green infrastructure is complex. When you follow the thread from policy to strategy, implementation and then through to delivery, construction and value management, there are too many gaps in the decision-making processes where original intent is watered down. Often left to the last part of a design process, adding in trees becomes an afterthought on large projects. Conversely, if we were to take on the challenge properly, they should be the starting point.

Australia is in the midst of an infrastructure investment boom. We’ve seen funding for projects which have been discussed for the past 25 in some case 50 years come to life. Infrastructure projects are notoriously contested spaces dealing with the needs of infrastructure, standards for utilities and a mixture of public and private land ownership. This makes the the approach to delivering minimum canopy tree coverage targets complex and has varying levels of success. That said, these projects offer a scale of opportunity to contribute to canopy tree coverage targets that is unmatched. A coordinated effort to bring all stakeholders on the journey and signed up to specific targets can reap massive rewards for the environment.

Exemplar projects such as Melbourne Metro Tunnel are committed to doubling tree canopy cover by 2040 as stated in the Living Infrastructure Plan[1]. This project and the people administering it are paving the way to building industry knowledge, testing methodologies and delivering ambitious outcomes. This has only been possible through the involvement of specialists with technical knowledge at all points within the project lifecycle leading the way.

Extensive tree planting is planned as part of the Melbourne Metro project (image: MT Metro Tunnel Living Infrastructure Plan)

Urban Ecologists, Landscape Architects, Horticulturalists, Environmental Engineers and Planners and Urban Designers have the skills and knowledge to drive great outcomes. Integrating their knowledge into defining rigorous policy and gathering support from the top down has been coupled with setting realistic targets in the projects contracts and developing resilient design solutions from the bottom up.

There are several lessons which could be learned from projects like Melbourne Metro Tunnel Project and initiatives such as Greening the West[ii]. Further industry wide discussion is required to share these lessons and gather inputs from all disciplines to improve.

Ideas which have been floated and require further industry discussion include.

• Simplifying governance by creating a Green Infrastructure Authority at a state level that has the remit to coordinate, provide oversight and review canopy tree targets across all steps in policy and project lifecycles.
• Understanding the scale of opportunity by undertaking an audit of public land, engaging with state and local government departments, utility authorities, and major project delivery teams to paint the picture of what is possible to achieve and what impact that will have collectively.
• Setting clear targets. Every project which has an impact on Green Infrastructure, either on private land or public land must be held accountable to deliver on clear targets.
• Planning and measuring. Create universal tools for measuring, predicting and administering the delivery of minimum canopy tree targets which can be referred to by strategic planners and project managers.
• Tracking progress from policy through to delivery.
• Understanding the various barriers at each level and work towards removing them.
• Collating the lessons learned on multiple projects and share them in frank conversation with the broader construction industry, not just those that are experts.
• Celebrating each scale of the wins.

There is a lot to like about the shift in conversations around canopy tree coverage and its importance in mitigating urban heat island effect, creating liveable places and bringing communities together. The diversity of voices calling for change and working towards great outcomes is encouraging. It’s not only the green thumbs at the table – we’re seeing engineers and value management teams aligning on this issue.

The built environment industry needs to grasp this momentum and continue to improve at all points of a project lifecycle.

Above all, the industry needs to grit our teeth and take trees out of the ‘too hard basket’.

[1] https://bigbuild.vic.gov.au/__data/assets/pdf_file/0016/111832/MT-Metro-Tunnel-Living-Infrastructure-Plan.pdf

[i] https://www.planning.vic.gov.au/policy-and-strategy/planning-for-melbourne/plan-melbourne/cooling-greening-melbourne/mapping-and-analysis-of-vegetation,-heat-and-land-use

[ii] https://greeningthewest.org.au/

Sarah Bridges 
Principal Design Integrator, Aurecon

Sarah is a passionate urban designer and design manager with over 18 years of experience leading interdisciplinary teams on complex city shaping projects. Through her experience of advising and leading projects across numerous sectors in Melbourne, Europe and China, she understands the impact built environment projects play on living systems within cities and precincts. She strives for design excellence in improving not only the outcomes of projects but the process of how decisions are made.