Trans Scan: a global scan of emerging trends in mobility and the built environment

Sustainable Cities

December 2001

Summary

Although we have not specified what we mean by sustainability, and therefore what we mean by sustainable cities, we have accumulated enough scientific evidence to suggest that the effect of human agency on local and global ecosystems resulting from the way we live is irrevocably damaging the environment and its capacity to support human societies.

This paper argues that the form and structure of the city contributes to the present generation of environmental stress and that we can significantly reduce that stress without sacrificing living standards by changing the form and structure of our cities.

Introduction

Australia's urban areas are the locations where the greater proportion of the nation's wealth is created and held and where the culture of the nation finds expression. In this most urbanised of nations, the cities and urban areas are also the locations where the great proportion of the population engage in a wide variety of economic, social and political pursuits.

Our cities are our most intensively shaped landscapes. They are the most heavily overlaid and inscribed by the pipes, wires, roads, tracks and cultures that reflect and represent our aspirations for the present and our images of the future. They are the locations of much pollution, are the generators of much of the greenhouse gas emission, the greater part of the waste stream and the demands for water, which have such a devastating effect on many of our catchments.

Over the past century we have witnessed increasing concern over a range of environmental issues. We have expressed that concern in a variety of ways and taken a series of initiatives to minimise what we used to call 'externalities'.

The development of water supply, sewerage and drainage systems, the regulations to control water pollution, the introduction of clean air regulations, the separation of residential development from industrial activities, the introduction of town planning all had a concern over environmental issues at their heart.

We now see that concern over the viability of the biosphere itself is rising and that rather than be seen as 'externalities' environmental issues are of central importance.

We have begun to recognise that the natural ecological systems cannot continue to function as they have done if we continue our present practices in the exploitation of natural resources. Although our understanding of the natural processes which occur, and how they might be affected, is incomplete there is enough evidence to accept that we have exploited or driven various species of flora and fauna to extinction and have compromised the lives of others, in the process reducing the diversity of the biosphere.

Our farming practices have led to desertification, and our clearing of forests has increased flooding, erosion and salination. The consumption of fossil fuels has led to a great increase in CO2 in the atmosphere. Our activities have created major holes in the ozone layer with consequential threat to the stability of the biosphere. We suspect that forest clearance and the increase in CO2 lead to climate change which, together with the holes in the ozone layer create major threats to life sustaining ecosystems.

We are struggling to cope with mountains of waste which themselves become major threats to ecosystems. Clearly, cities and rural regions exist in a symbiotic relationship so I do not intend here to imply some kind of city versus the country tension. That is simply an unproductive avenue of exploration but it is important to recognise that many of the stresses on our rural ecological systems originate in demands placed on them by the demands of urban populations for food, water and other natural resources.

Attempts to establish some kind of city versus country dichotomy in the approach to resolution of environmental issues is currently used by the Commonwealth as a device to focus on the regions. The specific exclusion of cities from the initiative to combat salination is simply one illustration of this myopia. Unfortunately this dichotomy also a device used by many in the city to avoid accepting responsibility for the stresses the city places on the environment.

Nonetheless we have enough scientific evidence about the effect of human agency on local and global ecosystems to accept that the way we live is ecologically unsustainable.

Sustainability

The word 'sustainability' however, means what speaker and listener want it to mean. On some estimates it is now differently defined in 150 pieces of legislation in Australia. Some argue that this is a strength, that there is value in the lack of precision. We might accept that there is great value in our kind of democracy in public processes of debate but this should not preclude striving for consensus on what we might mean by sustainability at any time.

In 1992 Dovers and Handmer defined Sustainability as 'the ability of a natural, human or mixed system to withstand or adapt to, over an indefinite time scale, endogenous or exogenous changes perceived as threatening. Sustainable development is a pathway of deliberate endogenous change (improvement) that maintains or enhances this attribute to some degree, while answering the needs of the present population.'

They went on to make the point that 'sustainability is thus a long term (and probably fanciful) condition, and sustainable development the variable process of moving closer to that condition.'

These definitions lack precision which has often led to governments, including local government, appearing to create uncertainty, confusion and ambiguity among residents and developers. The lack of precision is a not a strength in our legal system which inevitably seeks to establish clarity and to reduce ambiguity. If the planning system, including the process of public debate, does not provide definition or give meaning to the notion of ecologically sustainable development, the courts will.

While ecological sustainability is seen by some as problematic and by others as unattainable the reality is that Australia must adopt the strategy of a transition to sustainability by attempting to systematically reduce environmental stress.

Nowhere is this strategy more important than in the cities given their central role as sources and locations of environmental stress. It is important also because systems which import all their energy, water, food and raw materials and exports their waste are, by definition, unsustainable. Modern cities are examples of such unsustainable systems. The challenge is to make them less unsustainable.

In pursuing the transition to sustainability, general economic settings and mechanisms, including the suite of pricing strategies and taxes, are important.

However, planning tools and aids to decision making are needed which will complement them and allow the introduction of location and space issues into the consideration of policy options and development proposals.

One of our tasks, then, is to progressively invest the word and concept 'sustainability' with a meaning which could be socially enacted with substantive outcomes. Another is to develop a planning system so that sustainability issues can be considered systematically and democratically in the planning and development of the cities and regions.

In developing such a planning system the first thing we must acknowledge is that there is no 'end point'. We must recognise that we are engaged in a process by which we set goals and targets which we strive to meet over a specified period knowing that the goals and targets will be continuously revised. That is, the notions of 'sustainability' and 'sustainable development' will be incrementally, progressively defined and we will periodically arrive at new consensual definitions.

Urban planning

For half a century we have employed land use planning as a way of pursuing social, environmental and economic goals in the development and operation of urban and regional areas, although economic goals have been given the greatest weight.

It has always been difficult to say with certainty that particular intensities or arrangements of uses would lead to specific outcomes. The identification of land uses were, at best, only ever crude approximations of the nature of activities, the connections between them and the 'externalities' associated with them. That is, land use planning relied to a very large extent on the precautionary principle in pursuit of these goals.

Planners were for a time able to convey confidence that their prescriptions and recommendations about the uses to which specific pieces of land should be put, based on this precautionary principle, would produce the felicitous social, environmental and economic outcomes collectively sought.

A great deal of regulation was justified and built on this expression of trust - this belief in the efficacy of the decisions made by planners - and there is no doubt that it frequently produced congenial results. But there were also many instances where the lack of specificity or where the relationship between the activities proposed for a particular piece of land and the social, economic or environmental outcomes of those activities were vague or contested and which led to courts becoming involved in providing the precision or determining the relationship. A great deal of case law evolved to buttress this, which might have been a comfortable outcome for many lawyers but it thrust courts and judges into playing the role of planners - a role for which they were not necessarily well suited, nor did they welcome it.

By the 1980s the notion of scientific planning was unpopular. Urban planning which had never been central in government decision making was even more marginalised. The public appeared to lose faith in politicians and instruments of government. The role of government was challenged and large areas of administration and service provision were deregulated or privatised. For a variety of reasons, not all of them due to the fallibility of planners, the land use planning practices followed could not cope with changing demands to accommodate growth or with the simultaneously increasing concern over environmental issues.

From the mid 1970s State and Federal governments were seized by a preoccupation with 'short-termism' a kind of virus which degraded the sensibility of politicians as they succumbed to the pressures and blandishments of entrepreneurs and their financiers. They were led to the belief that if they did not make the quick decision and respond instantly to the imperatives of the 'market', and especially to the international entrepreneurs and financiers, cities would 'miss out' and be left behind.

The current expression of concern over sustainability can, to some extent, be seen as a reaction to the limitations of narrowly conceived considerations of environmental impacts arising from pressure from entrepreneurs and their financiers for quick responses to their proposals. That is, the concern stems from anxiety that long term environmental consequences of developments are overlooked in favour of alleged short-term benefits.

The current expression of concern is also recognition of the global impact of many of the environmental stresses cities experience and generate. This recognition is tending to force governments to seek ways of ameliorating both the source and effects of the stresses.

How should we respond to this situation? How should the threads of the frayed town and regional planning system be pulled together to weave a stronger web which takes fuller account of environmental issues in the pursuit of social, environmental and economic goals?

Path dependency

To provide discipline or focus in this kind of dynamic planning we typically set a period which is 'realistic' - not too short to have no effect yet not so long as to be fanciful or regarded as so far in the future it will not affect behaviour or expectations. For the purpose of much of our planning we have tended to set horizons of twenty years.

While this period is arbitrary it is long enough to enable us to make significant changes to the infrastructure of our cities such as water supply, sewerage and drainage systems, road and rail networks, together with the rail rolling stock, and ferry and vehicle fleets, etc. It is long enough to make significant changes to other elements of the built environment, assuming current levels of building and construction activity. It is also long enough to make progress in achieving sustainability goals in the production and consumption of a range of services and in commercial and manufacturing processes.

The major disadvantage of such a horizon is that it is beyond the political cycle. This is particularly important in the approach to ecological sustainability. It has taken two centuries for some of the environmental issues to become critical and it is fanciful to imagine that we can quickly solve the problems. Salination, for example, has been with us for some time but it is only recently that its full magnitude has been accepted and the need for an imaginative large scale, continuing effort over a long period to reduce or eliminate it has been recognised. Even here, however, for a variety of reasons, the significance of salination and waterlogging in urban areas remains unrecognised.

Over the next twenty years the inherited form and structure of the cities will largely affect the provision of urban services in our cities, their provision will also, of course, be affected by the characteristics of the present investment in them.

This is not to say that planning for transition to sustainability is governed by the path dependency created by a city's past pattern of investment in fixed capital in buildings and structures - the physical fabric of the city - or in the fixed rail rolling stock, vehicle, or ferry fleets. It is simply that recognising the significance of the past helps identification of the difficulties which must be anticipated and planned for in proposing how urban services may change or may be changed. It also helps in the assessment of the environmental benefits that may be expected to flow from such changes.

Although the process of urban change is generally slow the process of change in some areas may be rapid (especially in areas where tall buildings are built). That is, the form of development in critical areas of the city may change very rapidly and certainly much faster than the capacity of the infrastructure that supports them can. This inevitably leads to stresses in the systems and tends to distort the patterns of investment in urban infrastructure.

Current land use planning approaches cannot provide an appropriate assessment of the nature or magnitude of the changes or whether they are more or less sustainable.

Transition to sustainability

A new approach is needed which integrates the concerns of the scientist/ecologist and the measures they can provide of the environmental effects of exploitation of resources with those of the urban planner who can facilitate the introduction of social, economic and aesthetic considerations into the expression of technocultural choices.

The components of an ecologically sustainable future for our cities can only be achieved by deliberate transitions from current practices to different ways of acting. One way of facilitating the transition would be to develop a different approach to the planning for and accommodation of the activities carried out in the city.

This implies a departure from the present approaches to land use planning, one which would allow planners to assess alternative development strategies for the physical fabric of the city, for investment options in urban services and in the structure and operation of manufacturing, warehousing and retailing. It also implies both increasing the awareness of people at all levels to the importance of ecological sustainability objectives and their inclusion in decision making designed to the achieve those objectives - this requires a philosophy of participation in decision making.

The word 'transition' suggests that we need to facilitate the expression of a range of interpretations of the existing situation in a city before we can begin to evaluate possible alternative directions for their growth and management. The word implies a state of flux, of development over time. It means a preparedness to accept that there are different problems which may emerge in making the transition from the present to the alternative futures to make them more sustainable and that it will be necessary to identify and adapt to the problems in different ways at different times.

Although we could draw up a long list of the objectives we might pursue in a transition to more sustainable cities the three most important aspects of sustainability in the city are:

1. energy consumption and its relationship to greenhouse gas production;
2. water consumption and its relationship to sewerage, drainage and water pollution and the effect of sequestering river flows to provide the urban water supply on the ecology of their catchments; and
3. solid waste production, its minimisation and its recycling.

Making cities less unsustainable in terms of consumption of energy from non-renewable sources and of water consumption would also have the effect of achieving other sustainability objectives such as reduction in air and water pollution and protection of biodiversity.

The significance of energy and water consumption is that they both affect, or have the potential to affect, the form and structure of the city whereas the connection between urban form and structure and other sustainability objectives is weaker.

The production of solid waste, its minimisation and its recycling is a major issue in Australian cities. While much of its production is a function of the consumerist nature of society the opportunities for minimisation of waste and its recycling are affected by issues of urban form. Opportunities for recycling may also be affected by city structure.

By 'form' I mean the nature or density of development. All major cities in Australia are essentially low density, especially in their residential areas, although recently city centres have been developed to high density.

By 'structure' I mean the spatial relationship of services and activities, that is, whether they are structured in linear relationships, are highly centralised or whether the city is structured as an interconnected set of nodes around which development is arranged. All the large cities in Australia - Adelaide, Brisbane, Melbourne, Perth and Sydney - are highly centralised and have been since their foundation. This is partly a function of the period of their settlement and growth.

The centralisation of the city raises a profound and, to some extent, unavoidable paradox. There are social and economic benefits to be derived from a degree of centralisation of activities and social investment in cities. However, pressure for centralisation produces demand for more people to be at the centre of economic and political power and influence. This demand in turn becomes a demand for tall buildings to provide accommodation for the commercial and governmental activities we pursue. It may also become a demand for tall buildings for residential accommodation. It is also clear that at some point in city growth alienation, anomie, segregation and diseconomies of scale and centralisation arise.

The structure of the city is the main source of its inefficiency. The greater the degree of centralisation of the city and therefore of its urban services, the greater the inefficiency.

Continued focus on the development of the CBD leads to continuously increasing demand for several urban services, including especially, transport. Increased centralisation forces travel through the centre even of those who do not have the centre as their destination. This in turn leads to the kind of congestion problems now experienced on road and rail networks in Australian cities.

We of course need and desire a degree of centralisation but the challenge is to find the degree that gives us the best trade-off in terms of the sustainability of the city. The benefits of centralisation might best be achieved in large cities by developing the city as a 'set' of nodes connected by high quality, frequent public transport services.

Energy consumption

Energy consumption falls into two categories:

1. embodied energy, that is, the energy used to manufacture the materials used in the dwelling as well as that used in the fabrication of components and in its construction as well as the energy used in the building 'waste'. The energy embodied in dwellings, buildings, structures and infrastructure services might properly be regarded as invested energy or energy capital in the form of the built space; and
2. operational energy, which is the energy expended in the pursuit of activities carried out in urban areas, including the energy residents use to live in their dwellings.

At present we are developing energy rating schemes for dwellings to encourage designers, builders and owners to become aware of the energy expended in their operation. This initiative is highly contested (Williamson 2000). At its best it might be a useful first step but the desired economies in energy consumption achieved this way can only be achieved by particular behaviour which may be inconsistent with the way households actually live in or use a dwelling.

Of greater concern is the fact that the energy rating system does not refer to the energy embodied in the dwelling. Nor does the energy rating system take into account the context of the dwellings or relationship of buildings and structures to one another. That is, the energy rating system does not relate to the urban space created by the agglomeration of buildings and structures.

Embodied Energy

Tucker, Salomonsson and Macsporran in (1994) estimated that the embodied energy of the Australian national building stock at 22,500 petajoules was equivalent to about nine years of total energy consumption. About 40 percent of this embodied energy was estimated to be in the residential building stock. This estimate of embodied energy takes no account of the embodied energy destroyed by building demolitions nor does it estimate the embodied energy in the infrastructure.

Tucker and Treloar (1994) further estimate that 'CO2 emitted over the years in stock production... was estimated to be approximately 2200 MT (million tonnes)'. If the building stock is growing by 1 percent per year and the average life of buildings is 100 years that would mean 450PJ of energy was being used per year. (The average life of buildings in the stock is, and is likely to continue to be, significantly less than 100 years which means that this is a significant underestimate energy consumption in embodied energy.)

Suffice it for our purposes to note that Tucker and Treloar (1994) acknowledge that the 'construction sectors are one of the main contributors to energy consumption and CO2 emissions nationally.'

Because taller buildings use more energy expensive materials we might expect that their embodied energy per unit area is higher that that for low rise buildings.

I am unaware of definitive studies of the embodied energy per unit area in tall residential buildings compared with tall office buildings, although conventional wisdom has it that, for all practical purposes, they are the same for buildings of equal height and that both are much higher than for conventional forms of dwellings.

We do not have a citywide breakdown of the embodied energy in either residential or the non-residential buildings so we cannot comment with any accuracy on the proportions of the embodied energy invested in different forms of development. That is, we do not know what proportion of the embodied energy of either residential or non residential buildings is in the form of tall buildings. It would be safe to assume, however, that the proportion is increasing because we now have many more tall buildings than we did, say, 20 years ago and the proportion of the residential stock now in the form of tall buildings has increased.

Current research into the embodied energy of detached, semi detached and attached two storey house types (Fay, Lamb and Holland 2001) indicates that, for the same sized dwellings, there is virtually no saving in embodied energy between the three types of housing generally found in Australian cities. The research suggests however, that the traditional detached houses have a greater capacity to use materials with lower embodied energy. The authors conclude that the 'compressed suburbia' produced by the preoccupation with consolidation policies might lead to increased urban density but it does so at the expense of the pursuit of sustainability objectives.

Weatherboard houses embody one-sixth the energy of brick veneer houses and timber framed houses store carbon whereas steel framed houses permanently release carbon to the atmosphere. Yet in some of our cities we energetically construct yet more houses with steel frames. The full effect of the substitution of timber for more energy expensive materials depends to some extent on the source of the timber, that is, whether it comes from old growth forests or plantations and whether it has to be transported over long distances (Holland and Holland 1995).

There may be few opportunities, given present technology, for the production of tall buildings with lower levels of embodied energy. Whether we can reduce the embodied energy in tall buildings depends to some extent on whether we can devise new approaches to their heating and ventilation and to some extent on the substitution of low embodied energy materials for the high embodied energy materials currently used. The magnitude of such savings in embodied energy is an empirical question for which we have not begun the research.

The transition to higher density housing, including that in tall buildings has increased rapidly over the last decade. Almost half of all new dwellings are in the form of tall buildings in some of the larger cities. Although we cannot provide accurate figures we know that the energy embodied in the favoured newer higher density residential developments greatly increases the amount of carbon permanently released to the atmosphere. That is, the forms of residential development currently favoured by governments and their planning advisors are significant sources of environmental stress.

These twin issues of the operational energy and embodied energy of dwellings are, of course, only two aspect of the operational and embodied energy of buildings and structures in the city. The issues become of great significance when we contemplate the embodied and operational energy of tall buildings.

Currently we permit the development of tall buildings even when we know that the materials from which they are built, that their methods of construction and the waste material from their construction are expensive in energy terms. The embodied energy at all steps in the manufacture of the materials, their fabrication and the construction of the buildings permanently releases CO2. In sum the greenhouse gas equivalence of the energy embodied in tall buildings constitutes a significant proportion of the annual release of CO2.

The embodied energy in infrastructure is also a significant element of energy consumption. We do not have much empirical evidence of the stock of this energy investment although some research is indicating the significance of this aspect of our cities. Pullen (1999) reports on a study carried out in an Adelaide suburb measuring the embodied and operational energy costs of the conventional provision of water supply, sewerage and storm water services. His comparison of the conventional provision of a water supply with on site collection and storage indicates that in areas with regular rainfall individual tank storage has lower energy consumption depending on the size and type of tank. This suggests that it may be appropriate for some areas of the city to foster the site collection and storage of water rather that rely on the traditional approach to the provision of a water supply. This response could be appropriate in both new development areas and in areas in which the existing infrastructure needs to be renewed.

We have so far only limited evidence but similar approaches to the local management of sewage especially by using new biological treatment processes may also lead to lower energy consumption. One of the beneficial aspects of such an approach is that the stormwater runoff problems would also thereby be reduced.

Operational energy

Most tall buildings rely on mechanical air conditioning and on the provision of lifts to make them habitable. That is their 'fixed' operational energy is also a significant source of greenhouse gas release. The energy used in the activities carried out in them is also from elaborately transformed sources, which are significant contributors to greenhouse gas production.

In some areas a high proportion of even low-rise buildings are mechanically air-conditioned. This may be due in large measure to the fact that modern developments allow few opportunities to plant trees and shrubs to naturally moderate local extreme climate variations. It is also due to inadequate attention being given to the design of buildings to minimise operational energy consumption.

In addition to the contribution of the 'fixed' operational energy of tall buildings to greenhouse gas production their heating and air conditioning may detrimentally affect the ecology of their local area. This might be reduced if the buildings were more energy efficient and more energy independent.

We similarly need more detailed information about the operational energy requirements of the city. In addition to the 'fixed' operational energy we need to develop our information about the transport energy demand of the city.

One area of inquiry into transport energy demand, which is advanced, is that relating to congestion. We express our concern over the contribution urban road congestion makes to greenhouse gas production - currently estimated to be 13 million tonnes - and we explore the use of economic mechanisms such as congestion pricing and parking charges etc to reduce demand. Some proponents of such measures claim reductions of greenhouse gases of as much as 40% could follow from the introduction of location specific road user charges (BTE 2000).

These savings would only be achieved if behaviour was modified by pricing mechanisms, which in turn led to changes in development patterns. It would make more sense to employ such general mechanisms if they complemented policies to distribute development across the metropolitan area to reduce the centralisation which generated the congestion in the first place. This would have the accompanying beneficial effect of producing cities which were also more equitable in their access to employment and the range of cultural and recreational opportunities the city has to offer. Such a policy might lead to fewer tall buildings distributed across nodes in the metropolitan area.

Life-cycle energy consumption

Current research into the life-cycle energy consumption of housing is revealing fascinating new results which gives hope that cities may be made less unsustainable. In a study of the life-cycle energy analysis of a 'green home' built in Victoria Fay, Treloar and Iyer-Raniga (2000) conclude that as operational energy becomes lower through a combination of efficiency improvements and life style changes the embodied energy becomes relatively more significant. They suggest that attention given to design flaws in new buildings and the substitution of low embodied energy materials for the high-embodied energy materials could reduce building embodied energy. They also suggest that renovation of existing buildings may also be a productive approach to the reduction of embodied and operational energy savings in the city.

Pullen (2000) found that the annual operational costs of 25 typical dwellings in Adelaide were 4 times that of the embodied energy of the houses, assuming a 50-year dwelling life. The estimate of embodied energy tends to be conservative which suggests that it is more significant that the ratio implies. This research does not separately identify the proportion of the operational energy which is consumed in heating and cooling. Heating and cooling is thought to account for about one quarter of the operational energy of the dwelling which means the embodied energy is approximately equal to the energy required to make the dwelling habitable.

Water consumption

The form of development affects the opportunities for reduction in water consumption and recycling and for moderating storm water runoff.

We do not have the space or time here to explore the situation in all Australian cities but use Sydney as an illustrative example where around 69% of current metered water use is for residential purposes.

Over the last decade a suite of demand management strategies has resulted in reductions of approximately 9% in the per capita daily consumption of water for residential purposes, including gardening which accounts for almost one quarter of consumption and equal to the amount used for showers.

Traditional forms of residential density permit a high level of water harvesting and storage. Coupled with modern recycling technology this form of development could lead to a significant reduction in the demand for water from the major storage and reticulation systems. That is, the consumption of metered water could be reduced if water was harvested from roofs etc, and stored for household use and the water used in laundries, baths and showers was recycled. The demand would be reduced even more if the trend to changed gardening practices to make greater use of native plants and the use of mulching was increased and if the recycling of water was to a standard which permitted the recycled water to be used in showers etc.

High density residential development, on the other hand, creates fewer opportunities for water harvesting although recycling could be, and has been, incorporated into some developments making them more independent of city sewerage systems. Per capita consumption of water in high rise residential developments is lower because there usually is a smaller area of garden associated with the developments.

The traditional lower density residential development produces less stormwater runoff than high density development which means it creates less stress on the local environment.

Commercial undertakings in Sydney consume about 9% of metered water use. The amount used for these activities has remained relatively stable over the last two decades largely due to pricing strategies which encourage undertakings to cut consumption.

Industrial water use in Sydney accounts for approximately 12% of consumption. The lower consumption is largely due to greater efficiency and recycling encouraged by water pricing strategies.

The level of per capita consumption of water varies between the cities as does the opportunities for water harvesting and recycling. In seems clear, however, that Australian cities could be made significantly more sustainable in terms of their water consumption if they were to introduce water pricing strategies which encouraged residential harvesting and recycling of water. This would have the added benefit of reducing the flows to sewage treatment plants and, ultimately, to sewer outfalls which typically are to the ocean. This option is more viable in forms of development in which there is the space to harvest and store the water and to accommodate the small scale recycling plants needed to process the water. One of its benefits is that it does not require changes to the traditional form of Australian cities although it may require a commitment to reduce the degree of their centralisation.

A strategy of greater reliance on local water harvesting and recycling assumes greater significance as Australian cities face the twin problems of shortage of capital for infrastructure investment in new developments and of replacing the present obsolete or worn out water supply and sewerage systems. The paper by Pullen (1999) referred to above which examined the embodied energy costs of different ways of providing water supplies supports this contention.

A strategy of greater self reliance and therefore independence of housing may also be forced on cities as the demand for water reaches the limits of the water available from near city catchments. That is, harvesting and storing rainwater may make cities more sustainable because they will make lower demands on near city catchments, reduce stormwater run-off and, if coupled with local recycling, reduce off-site sewage flows.

Waste production

The production of waste is more a function of attitude and life-style in a high-level consumerist society than it is of structural elements or the physical fabric of the city. It is important to note however that the reduction of waste in the building process in the re-use of 'waste' materials and in the recycling of material from demolition of buildings etc has been significant.

The campaigns to get residents to reduce or separate out the flow of waste materials have been successful so that much waste which once was sent to landfill sites is now used to produce compost or is recovered for use.

The reduction in waste in the form of sewage flows might also be achieved by changes in the behaviour of residents and changes in commercial and industrial processes. For example it may be necessary to place a high tax on the use of high phosphate detergents and cleaners etc in favour of detergents and cleaners which do not create additional loads on sewage treatment processes. In residential areas where the sewage is relatively benign such an action would make it easier to operate local sewage treatment plants to produce effluents which could be re-used locally.

A new planning paradigm

The present planning and development process fails to give weight to consideration of the ecological sustainability of the city.

Governments and environmental groups have tended to focus on pursuit of global targets for reduction in consumption of renewable energy and therefore greenhouse gas production and on general targets for reduction in water consumption. They have tended to focus on simple market mechanisms including the transferability of pollution rights and to pursue carbon trading schemes and the like. There is no doubt that general targets and market mechanisms are important but to achieve the targets we must employ mechanisms which allow greater discrimination in the use of location specific measures. That is, we have to be able to direct the development where we want it to occur and of a form we want to minimise the degree of unsustainability.

We need a new approach which recognises at once that we must look at the way a city develops and is operated to identify potential ways to reduce energy and water consumption and waste production.

Comment

What does this exploration of the transition to sustainability tell us?

The first lesson to be drawn is that if we are to be serious about sustainability and expect others to take us seriously about our pursuit of this objective - especially when it bears on international obligations to pursue targets such as those to reduce greenhouse gas production - we need to develop the measures of energy and water consumption and waste production in our cities.

We need such measures to be able to show how well we are achieving the targets we have set or have agreed to. We need the measures to be able to convincingly make the case for the policies we must follow in pursuing substitution of high embodied energy materials for lower embodied energy materials. We need such measures to develop the performance based regulatory framework we aspire to.

We already have regularly updated spatially organised data related to a large number of the factors which bear on energy and water consumption. At present these data sets are separately collected and maintained according to different definitions of economic and social activity and expressed on different spatial bases. It wants for us to take the simple decision to coordinate the collection and presentation of the data in such a way that we can produce measures of the performance of our cities at different times. That is, it seems to be a simple problem of coordination between the agencies and corporations, most of them in public ownership or at the very least subject to a high degree of public regulation, to produce a data set which relates the consumption of energy and water to the areas in which the energy and water is consumed and the people who consume the energy and water.

The second lesson to be drawn is that while we cannot be sanguine about it we already have encouraging evidence from empirical research in Australian cities that we can achieve many of the sustainability objectives in reducing energy and water consumption without sacrificing standard of living and amenity of the cities.

The third lesson is that the indications are that with a better spatially based data set relating to energy and water consumption we no longer need to pursue urban development policies which are not soundly research based.

The fourth lesson is that to achieve progress in the pursuit of sustainability we must be prepared to critically explore some of the fundamental assumptions, often implicit, which underlie the approach we take to the form and structure of the city and of the way we meet demand for services such as energy and water supply. This might well force us to re-examine the institutional framework of decision-making - an aspect of the pursuit of sustainability which has not been explored in this paper but which deserves to be.

While most of the research referred to here explores issues related to urban form and may be seen by some as a contribution to debates about compact cities its underlying concern is about issues of structure. The point is that once we are able to assemble data about the energy and water consumption and waste production of the existing city structure we are able to consider alternative arrangements of activities. Once we recognise that we can dispose our activities in whatever arrangement best suits our pursuit of sustainability objectives we begin to accept that we need not be dependent on the provision of highly centralised services. This frees us to consider how we can structure our cities in the most congenial manner and to be able to measure the kinds of tradeoffs we must inevitably make in each city to achieve that goal.

Meanwhile, we can reasonably expect our planning authorities and agencies to provide leadership in adopting a strategy of transition to sustainability.

References

Bureau of Transport Economics (2000) Urban Congestion-the implications for Greenhouse Gas Emissions. Information Fact Sheet 16, 4.

Dovers, S R and Handmer, J W (1992) Uncertainty, sustainability and change. Global Environmental Change, 2, 262-276.

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