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Could money one day grow on rooftop trees?

Lately, I’ve been spending a lot of time staring at blank brick walls.

Whenever I’m in Melbourne, I find myself doing this, and the question that always springs to mind is the same: “Why is nothing growing on these walls?”

In a city that’s generally quite efficient at filling empty spaces, the uncounted hectares of unutilised vertical space stay largely barren, year after year. This is despite an abundance of ways to cultivate vegetation vertically, and a broad evidence base on the many benefits of urban greening.

Recently, I did a bit of looking into the reasons for this lack of change, and the most straightforward answer I could find is that it isn’t directly profitable for anyone to green up these empty spaces. In fact, some green walls and facades can be quite expensive to establish and maintain. The same is true for green roofs, which can quickly perish if the wrong species and soils are used.

Despite the costs, the benefits of urban greening are substantial. Researchers have found that urban green roofs, walls and facades can reduce the urban heat island effect, reduce peak stormwater flows and improve air quality. Some studies suggest that urban greenery also reduces stress, increases property values, and even reduces patient recovery time in hospitals.

With such a suite of benefits, it’s worth asking how cities can encourage urban greening, since market forces alone aren’t doing the job at the moment. It may be that councils can get change happening by providing incentives – or even mandating greening. Around the world, governments are exploring options to green up urban spaces.

Melbourne is no exception. The IMAP (Inner Melbourne Action Plan) is an alliance of inner-city councils that recently completed a review of policy options for encouraging green roofs, walls and facades. The review identified quite a few options. One initiative that the review suggests is a reduced rates charge for buildings with green roofs, walls or facades. Other options to make greening more profitable might include fast-tracking of permit applications, waived planning fees or exemptions from some planning requirements. If set at the right level, these incentives have the potential to spark a wave of green developments on both new and existing buildings.

However, when I asked Dr Dominque Hes, a Senior Lecturer in Architecture at the University of Melbourne, whether an incentive like a rates discount would do the trick, she cautioned against silver bullets:

A discount on rates or drainage fees could certainly get the ball rolling, but money isn’t the only challenge we face. Green infrastructure generally needs reliable irrigation and regular maintenance. It’s a novel concept to many building owners, and it can go wrong. When you’re talking about quite substantial capital outlays for unfamiliar building upgrades, the risk of failure can be offputting.

Dr Dominque Hes, Senior Lecturer in Architecture, University of Melbourne

Fortunately, this sentiment is reflected by IMAP’s policy review. While financial incentives will help, councils have a role to play by setting good examples on public buildings, as the Victorian EPA has done with the green wall outside its offices on Victoria street. The review suggests that councils will also need to reduce unnecessary regulatory hurdles such as permit application requirements for small green infrastructure developments.

For some building owners, recognition might be as powerful an incentive as money. Rating schemes for building energy efficiency, like Green Star or NABERS, generally don’t give green roofs or walls much in the way of credit. This is despite the potential for greening to reduce cooling requirements in buildings. If having a green roof meant an easier path to a Green Star rating or a less demanding NABERS retrofit, some of the CBD’s blank walls might quickly go green.

Some cities have taken a different path. Cities including Toronto, Stuttgart and Copenhagen are opting for regulation on top of encouragement, in a bid to green up the city’s rooftops. For example, permit applications for most new buildings over 2000m2 in Toronto must have green roofs covering at least 20% of the total roof area.

Of course, any successful set of new policies to encourage greening must be accompanied by solid guidance on how to do this greening. Fortunately this guidance already exists; the IMAP’s Growing Green Guide gives a fairly thorough run-down on how to design, build and maintain green walls, roofs and facades.

With such an array of policy options, and an excellent information resource already in place, the ball is now in the court of policymakers. Watch closely in coming months as councils plan their next moves.

This article first appeared at Tract Consultants. For further information and additional articles, visit the Tract news portal.

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