Green Infrastructure

Incorporating Plants and Enhancing Biodiversity in Buildings and Urban Environments

John W. Dover

• Publisher: Routledge
• Year: 2015
• ISBN:
  9781136330735
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

With more than half of the world's population now living in urban areas, it is vitally important that towns and cities are healthy places to live. The principal aim of this book is to synthesize the disparate literature on the use of vegetation in the built environment and its multifunctional benefits to humans. The author reviews issues such as: contact with wildlife and its immediate and long-term effects on psychological and physical wellbeing; the role of vegetation in removing health-damaging pollutants from the air; green roofs and green walls, which provide insulation, reduce energy use and decrease the carbon footprint of buildings; and structural vegetation such as street trees, providing shading and air circulation whilst also helping to stop flash-floods through surface drainage. Examples are used throughout to illustrate the practical use of vegetation to improve the urban environment and deliver ecosystem services.

Whilst the underlying theme is the value of biodiversity, the emphasis is less on existing high-value green spaces (such as nature reserves, parks and gardens), than on the sealed surfaces of urban areas (building surfaces, roads, car parks, plazas, etc.). The book shows how these, and the spaces they encapsulate, can be modified to meet current and future environmental challenges including climate change. The value of existing green space is also covered to provide a comprehensive textbook of international relevance.

1

WHAT IS GREEN INFRASTRUCTURE?

This chapter will:

• review some existing green infrastructure definitions

• present a modified definition of green infrastructure

• identify the reasoning behind the need to reduce the amount of sealed surface in urban areas.

1.1 Why green infrastructure?

I have been interested in green infrastructure, on and off, for a long time, since the early 1990s, even though it wasn’t called green infrastructure then. In the dim and distant past, I worked for an environmental consultancy company, and one project I handled was to produce the evidence base to support the green corridors policy which Kirklees Metropolitan Borough Council (based in Huddersfield) were proposing for their Unitary Development Plan. It was clear to me then that green spaces and biodiversity in towns provided a number of benefits to the community (and I mean this in the broadest sense of people, public services and enterprises) and I recommended that they recognised that in their policy (Dover, 1992). Moving back into academia, I subsequently did some rather more esoteric work on wildlife corridors (Dover & Fry, 2001) and urban ecology (Dover, 2000), amongst other things, and in 2006 worked for the regeneration agency Renew North-Staffordshire on ‘embedding green infrastructure in housing market renewal’ (Dover, 2006a, 2006b) which ‘renewed’ my interest in using biodiversity to deliver important ‘ecosystem’ services to humans.

Ecosystem services are generally considered to be of four types:

• Supporting services, e.g. nutrient and water cycling, soil formation, primary production

• Regulating services, e.g. climate control and pollution removal

• Provisioning services, e.g. food, medicines, building materials

• Cultural services, e.g. societal appreciation of nature and environment (EASAC, 2009).

I passionately believe that green infrastructure is the only way to cost-effectively meet some of the most important environmental challenges we face in urban areas; challenges that we will have to meet continuously over the coming decades, and perhaps even over centuries to come. There are many good reasons for creating green infrastructure, but one which is of singular importance is coping with the impacts of climate change, and the associated intensification of other environmental problems such as air pollution.

1.2 Definitions of green infrastructure

Perhaps I should make it clear from the start: when I use the word ‘green’ I mean using plants, vegetation or even microbes (even those that are not green). So ‘greening’ buildings means, literally, growing plants on, around, up, or even in them. I will not be using the term for other more technological approaches to reducing the environmental impact of operating buildings such as using ground-source heat pumps (Cho & Choi, 2014) or in the sense of a ‘green’ political movement.

Green infrastructure is often seen as being about the value of ‘open’ green spaces, and mainly emphasises pre-existing ones. Definitions which exclude the built environment are unhelpful in that they do not give a policy steer to the greening (literally, with vegetation) of sealed surfaces (e.g. Benedict & McMahon, 2006; Goode, 2006; TCF, 2011; and NWGITT, 2007). In the UK the Town and Country Planning Association (TCPA) defined green infrastructure in this way:

Green Infrastructure is the sub-regional network of protected sites, nature reserves, greenspaces, and greenway linkages. The linkages include river corridors and flood plains, migration routes and features of the landscape, which are of importance as wildlife corridors.

Green Infrastructure should provide for multifunctional uses i.e., wildlife, recreational and cultural experience, as well as delivering ecological services, such as flood protection and microclimate control. It should also operate at all spatial scales from urban centres through to open countryside.

(TCPA, 2004)

Yet ironically both the TCPA (2004) and Goode (2006) whilst using a definition that excludes building-related structures actually include them as examples within their publications (e.g. green roofs and sustainable urban drainage systems). Whilst many definitions persist in excluding built-environment components, some newer ones acknowledge the built-environment features explicitly, but only in respect of a limited set of attributes. For example, this one concentrates on sustainable urban drainage:

Green infrastructure is management approaches and technologies that utilize, enhance and/or mimic the natural hydrologic cycle processes of infiltration, evapotranspiration and reuse. Green infrastructure approaches currently in use include green roofs, trees and tree boxes, rain gardens, vegetated swales, pocket wetlands, infiltration planters, porous and permeable pavements, vegetated median strips, reforestation/revegetation, and protection and enhancement of riparian buffers and floodplains.

(EPA, 2008)

Others use a vague term that allows inclusion, but does not effectively promote built-environment features as such. For example:

Green Infrastructure is a strategically planned and delivered network comprising the broadest range of high quality green spaces and other environmental features.

(NE, 2009a)

The term ‘other environmental features’ was used in the UK government’s White Paper on the natural environment (Defra, 2011b), although it is unclear exactly what these features are as they are not defined. Nevertheless, the document cites an example that includes green roofs and walls and refers to the Flood and Water Management Act 2010 that has provision for encouraging sustainable urban drainage.

So my preference would be for a definition such as (NE, 2009a) but which is more explicit. For example:

Green Infrastructure is a strategically planned and delivered network comprising the broadest range of high quality green spaces and other environmental features including surfaces such as pavements, car parks, driveways, roads and buildings that have been modified to incorporate biodiversity and promote ecosystem services. (italics = my text)

The definition used by Tzoulas et al. (2007) is pretty good and seems to cover most eventualities and in very few words:

all natural, semi-natural and artificial networks of multifunctional ecological systems within, around and between urban areas, at all spatial scales.

However, I have two remaining quibbles: 1) the last two definitions suggest a rather top-down approach and one which discounts individual features that have not been a priori included in some strategic planning and delivery vehicle – this seems perverse as surely green infrastructure is a sum of assets whether they fit into a strategic framework/network or not; 2) these definitions stop at the entrance to a building – I do not see why this should be so as ecosystem services can be delivered by biodiversity inside buildings as well as outside. So the definition which I will be using is:

Green infrastructure is the sum of an area’s environmental assets, including stand-alone elements and strategically planned and delivered networks of high-quality green spaces and other environmental features including surfaces such as pavements, car parks, driveways, roads and buildings (exterior and interior) that incorporate biodiversity and promote ecosystem services.

Now, having settled on a definition I am happy with, I am going to blithely ignore a huge chunk of it. Whilst I want to give an overview of the values of green infrastructure in the first part of the book, I want then to concentrate on the ‘other environmental features including surfaces such as pavements, car parks, driveways, roads and buildings (exterior and interior) that incorporate biodiversity and promote ecosystem services’. Why? Principally because the ‘strategic network’ approach is well documented and a core component of spatial planning. The subtitle of the excellent book Green Infrastructure by Benedict and McMahon (2006) is Linking Landscapes and Communities, and implies – incorrectly to my mind – that GI is the preserve of the spatial. I do not want to give the impression that spatial planning or the creation and promotion of networks of green spaces, linkages, etc. is not important: it clearly is. What I want to do is show how a green infrastructure approach that embraces the modification of our existing non-green areas, piecemeal or strategic, can improve our environment. I want to show how we can ‘green the grey’.

1.3 Why should we want to ‘green’ buildings and reduce the amount of sealed surface in urban areas?

Whitford et al. (2001) identified four ways in which the ecology of cities is distinct from the surrounding countryside: 1) cities are warmer, 2) cities retain less water, 3) cities emit carbon dioxide, 4) cities have lower biodiversity; all these features are considered undesirable for one reason or another. These are generalisations, of course, and may not hold true in every case. Nevertheless, the point is that whilst cities are human habitats, humans are not very good at creating uniformly good ones for their inhabitants. The four features Whitford et al. (2001) identify are linked with poor environmental performance, but there are a whole clutch of others which impact directly and indirectly on human health which, for simplicity, can be bundled under the headings of ‘pollution’ and ‘green access’. Human health, physical and mental, has been shown to be better where people have access to good quality green space (Croucher et al., 2007; GSS, 2008) and especially that which is rich in biodiversity (Fuller et al., 2007). Sadly, the poorest people in our urban communities are also those with least access to green space, and tend to have the poorest health. Poor health is correlated with income (Deaton, 2002; Smith, 1999), and if you do not have much income, you tend to live in densely populated areas and eat less well than if you are rich (Alaimo, 2001). The housing stock you live in will be poor too: old, leaky and probably also more expensive to heat (Burholt & Windle, 2006). The health problems associated with poverty are exacerbated by lack of access to green spaces (Mitchell & Popham, 2008) and this disparity in access to environmental goods comes under the general concept of environmental justice (Haughton, 1999). Deprivation is, sadly, nothing new (Newman et al., 1990) and nor is the pollution that comes with urbanisation (Jacobson, 2002) and resultant health impacts (e.g. PM_2.5 related asthma (Kheirbek et al., 2013)) which we know that plants can help to reduce (see Chapter 2 et seq.).

If you live in a town or city, especially a large one, you will recognise that it generates its own climate – it is warmer than the surrounding countryside (Changon, 1992). I like snow and always found it frustrating when I lived in cities: we had miserable rainy winters, but as soon as I drove out of town, the countryside was covered in beautiful snow – you might not agree with my preferences, but the reality is that urban climates are different. Back in 1982 a seminal book was published called Urban Ecology (Bornkamm et al., 1982); it contained papers from the second European Ecological Symposium which was held in Berlin in 1980. I recall reading it some years later and being struck by the way that much work on vegetation was looking at how plants took up pollutants such as heavy metals (Greszta, 1982) and could be selected for tolerance to air pollution such as sulphur dioxide (SO₂) (Bell et al., 1982). In the same volume Horbert et al. (1982) published a paper summarising their research which identified the relationship between the proportion of sealed surfaces in an urban area (buildings, roads, pavements, etc.) and the resulting local climate which was: warmer (on average 0.5–1.5°C higher, 2–6°C higher on clear days), wetter (5–10% more precipitation), with higher levels of runoff, more polluted (gaseous pollution 5–25 times greater) and had lower humidity (winter 2% lower, summer 8–10% lower) and air circulation (windspeed 10–20% lower) than surrounding areas with a higher density of vegetation. In the same paper, Horbert et al. (1982) identified the ameliorating effect of urban vegetation on temperature (the central part of the 212 ha Tiergarten park was cited as being as much as 7°C lower in comparison with adjacent built-up areas) and that it could have localised impacts on the surrounding areas (depending on the permeability of the built-up areas so as to permit air movement). These urban climate issues are exactly the same challenges that face us now, but with increased ferocity due to the challenges of climate change, and some of the solutions are exactly as Horbert et al. (1982) identified: using vegetation.

So, we humans have not only changed our local environments for the worse, through overcrowding and pollution, but we have also changed the global environment (IPCC, 2007, 2014; Solomon et al., 2007). Very few serious scientists doubt that global climate change is real and that it is caused by human (anthropogenic) activity, principally through the burning of fossil fuels (IPCC, 2007). We know from modelling that one of the consequences of global climate change is that weather is going to become more unpredictable with extreme events such as heatwaves and severe storms becoming more frequent. Extreme events such as heatwaves kill people (Golden, 2004; Rey et al., 2007), extreme events like storms cause flooding (Starke et al., 2010). Towns and cities that have a lot of ‘sealed surface’ (buildings, roads, car parks) are less well equipped to deal with such, literally, lethal problems than those with a lot of green space (O’Neill et al., 2009).

In April 2013 the UK government published its National Adaptation Programme aimed at reducing the impact of climate change (Defra, 2013b) which ‘supports the use of green infrastructure’. So why is this book concerned largely with the ‘built’ part of the environment as opposed to large open spaces? It is partly to do with definitions and opportunities. Many green infrastructure definitions (see above) appear to exclude biodiversity on and in buildings and the benefits that it brings. This means that when policy is implemented and budgets set and spent based on such definitions, built-up areas are excluded. The reason for greening buildings and reducing the proportion of sealed surface is simple: if we don’t, we are going to have increasingly uncomfortable urban areas with low aesthetic value, high levels of pollution, poor climate, excessive heat, and flash flooding. In combination, this will have an impact on physical and mental health.

It is also my perception that most organisations have departments that work in silos and rarely work together or even appreciate the value of each other’s work. Green infrastructure, to many officers and political representatives in urban areas, means parks and nature reserves and the perception is therefore that it is really about aesthetics, recreation and wildlife. Of course managing such areas costs money, and viewed against the need for other essential services park management or nature reserve wardening appears a luxury and non-essential and, as a result, is often the first service to have its budget cut when times are hard. This view is, of course, to completely misunderstand what green spaces do, and to undervalue the wide-ranging benefits they provide to the whole community. Unfortunately, many current definitions (see above) have created new silo thinking: if green infrastructure is perceived as being only about green open spaces, then this is an important misconception. So this book aims to demonstrate: 1) the multifunctional values of green infrastructure generally – and how this cuts right across most of our concerns as citizens, and 2) to show how some aspects of the built environment can be modified to deliver many of these benefits in addition to green spaces. Why? The answer is very simple: few politicians are bold enough to suggest knocking down valuable buildings to create a new open space in the heart, or even periphery, of a town or city, but modifying built structures either by modifyi...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Acknowledgements
• 1 What is green infrastructure?
• 2 Benefits of green infrastructure
• 3 Indoors
• 4 Permeable pavements
• 5 Green walls
• 6 Green roofs
• 7 Street trees
• 8 Policy, regulation and incentives
• References
• Index