Green Infrastructure for Greener City Streets

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Wednesday, April 15th, 2015
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“We are the first generation that can end poverty and the last generation that can take steps to avoid the worst impact of climate change,” UN Secretary General Ban Ki-Moon has said. “Future generations will judge us harshly if we fail to uphold our moral and historical responsibilities.”

“It’s not only government. Government cannot do it alone. The UN cannot do it alone. There should be full partnership… then we should have civil society coming together. Even one normal citizen – they have a role to play. All these policies should be people centered – without people they are meaningless.”

Are our cities ready for a greener future? What should greener cities look like?  Is climate change still important and relevant?

For example, over 40 per cent of Adelaide’s carbon emissions are from transport – both public and private. This is one of the more difficult problems to address, as people need to get around and into the city for many reasons – to live, work and play. Equitable urban mobility is critical in our society.

Many of our city’s open spaces are often valued within a limited range – heritage, availability, and the fact someone it planned it that way. These are very important values, and ones we should mostly respect, but there are others that should be valued as equally, if not more.

Our existing green spaces, whether it is Sydney’s green belt from Pittwater around to the Royal National Park, Adelaide’s Park Lands, Melbourne’s parks, Brisbane’s river foreshores, or Canberra’s planned connected park system, currently perform a critical role in air-conditioning our cities by default.

Their role can increase dramatically through small changes (such as planting more trees and encouraging ecosystems to regenerate,) with a stronger focus on adapting the city’s streets. We need to adjust the optics on what our streets and highways achieve and the impact these critical assets have on the greening of our cities.

A typical city street is mostly paved with hard surfaces. Typically, this can be as high as 95 per cent of impervious surfaces such as footpaths, bitumen, kerbs and gutters. In our open spaces, it is mostly reversed. However, many of our valued opens spaces are sports fields, which often have limited environmental value. For example, irrigated turf offers little in the way of habitat and species diversity, nor does it have ecological value.

We must reinforce and recalibrate the environmental qualitative and performance measures as important in understanding our role in reducing the impacts of anthropocentric climate change.

An area of research and action that is gaining importance and relevance is the provision of ‘green infrastructure’ in our cities. It is one of the more constructive and outcome-driven strategies to combat climate change and carbon reduction.

Put simply, green infrastructure is a design-led approach aimed at climate adaptation on a city wide scale, offering integrated stormwater management, increased biodiversity, reduced urban heat island effects, cleaner water and soils, opportunities for renewable energy production, and increased habitat production. It also allows for human benefits such as better quality open spaces, increased health benefits, improved recreation and connected shade and amenity in our city’s spaces.

What does this look like? It can be as simple as cutting existing kerbs to new garden beds to take the first charge of stormwater, retarding the flow, reducing the pressure on the existing pipes, filtering particulates out, watering the garden, and dealing with certain pollutants almost at their source.

It can mean median strips performing greater roles as flood controllers, adding biodiversity, species diversity, reclaiming impervious spaces, creating habitats for insects including bees, adding visual value to our streets, creating interest and ownership from adjacent businesses and residents.

Who doesn’t like a nice garden? Our city streets are occupied by all of us, and we should care more for them. We have a role in creating great streets for ourselves and for our fellow citizens. Simply caring about our streets is a great start.

The current paradigm, however, reinforces the supply of hard utilities such as gas, power, water, sewerage, optic fibre, the NBN, drainage, telecommunications and other ‘services’ over the current greening of our streets. This is simply due to demand, cost and availability of space, and municipal management approaches. It is historic, and hard, to change simply due to the enormous costs of relocating services.

Consider the poor old street tree.

Prior to anything going into the ground, especially in city streets, it is usually the end of a long process, often involving a plethora of actions, strategies and compromises that make it difficult to even plant the actual tree. Current risk management approaches are more acute in tight city street contexts, and smaller, tighter, inner city streets are without trees largely as a result of this. There simply isn’t any ‘viable’ room for living things in the ground.

Our streets of the future will consider green infrastructure like any other piece of essential infrastructure. They will be greener, provide shade, pleasure, interest and somewhere to sit in the shade. They will collect seeds, leaves and mulch, provide habitat, cleanse our water and air, provide edible food, help drainage, enhance property values, reduce the need for expensive pipes and infrastructure, and create happier places for people. They will not only be beautiful, they will be measured on their environmental performance and provide an environmental return to the city.

Trees and landscape do add significantly more value than their installation costs or asset value.

If we flipped the approach, and gradually placed more emphasis on the benefits, we will see change.

We can measure greening benefits, through quantitative and qualitative measures, such as:

  • total number of shade hours in summer
  • solar penetration in winter, access to light for heating and passive heating
  • percentage heat reduction to pavements and buildings in summer
  • heating benefits in winter
  • connected shade (length) on our streets
  • reduction of stormwater drainage (i.e. smaller pipes)
  • reduced runoff into our creeks and rivers
  • ‘point source’ gross pollutant control (i.e. capturing rubbish at the source)
  • improved air quality
  • reduced reliance on air conditioning
  • number of operable windows
  • improved economic outcomes (increased trade or retail opportunities)
  • improved walkability/cyclability
  • improved property values
  • improved amenity (the happiness factor); and
  • desirability (the ‘hip’ factor, measured through engagement with people).

These measures are just for the street trees; the same and more can be measured for green roof and green wall initiatives, not to mention other carbon abatement schemes.

Many residents may have west-facing walls, for example. A simple vine planted to climb the wall can reduce the internal temperature by up to 10 degrees on a hot day, and conversely in winter can assist in passively heating the house if the vine is deciduous.

We currently plant trees in streets based on available space. We must trial new methods including how many trees we plant within a given area, challenging where feasible the distances to services, as well as investing more in research for more suitable species. Detecting damage to our city’s infrastructure should also include damage and insurance for large trees, not just the physical services.

These are pragmatic, achievable, workable, negotiable, and measurable outcomes. We can do most of these now. We can measure them now. It need not require significant additional investment; it requires some adjustments on current expenditure to ensure taxpayers money is spent wisely and with real, measurable (including environmental) outcomes beyond just assessing elements such as ‘asset class,’ ‘depreciation’ and ‘insurance value.’

If we are to retain our valued parks, reserves and gardens and preserve them without adjusting their environmental performance (i.e. to protect them as they are), we need to adjust, refocus and change our management practices, approaches, risk management, maintenance and public perception approach to greening our city’s streets and squares to do more of the ‘heavy lifting’ in combating the effects of climate change.

This is not a question of environmental values over economic and social values. It is one of addressing an imbalance and asking ourselves how we can best adapt now to reflect the inevitable changes affecting Australia.

It is real, it is here, and we can do something about it. It needs to start now. We can all do our bit without too much fanfare, and when we do, we can all reap the benefits. And we can preserve our existing open spaces the way they are and enjoy them for what we like, whilst the City can perform the role of a climate-adapted and carbon neutral city. The choice is before us.

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