AILA's landscape architecture occasional papers, articles and essays

ECOSYSTEM SERVICES FOR REGIONAL SUSTAINABILITY

Guy Barnett (about the author)

(an earlier version of this paper was published in 2001)

CSIRO Sustainable Ecosystems, Canberra

Ecosystem services are the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfil human life. Many of these services are now under threat from human activities.

This paper aims to highlight the value that our society derives from Australia's natural ecosystems and suggests several ways that design professionals can utilise these ‘free’ services to foster regional sustainability.

1.0 INTRODUCTION

Australia is one of the most urbanised countries in the world, with more than 85% of our population residing in major towns or cities (Newman et al 1996). Many of these urban residents consider themselves largely divorced from the natural and rural environment, due to increasing globalisation and high technological optimism.

However, this is far from the truth, as evidenced by the Sydney water crisis in 1998 that resulted in virtually all residents having to boil their drinking water, due to contamination. In this example, the source of the contamination was largely attributed to the poor ecological integrity and condition of Sydney's water supply catchments. The cost of this crisis to the state-owned utility Sydney Water has been estimated at $33 million (Stein 2000). Consequently, far greater focus is now given to catchment management activities that enhance natural water purification services.

This is just one example of the ‘free’ benefits that Australia's urban populations derive from natural ecosystems in their surrounding regions. Other important life-supporting functions include the purification of air, climate regulation, renewal of soil fertility, pest control, pollination and seed dispersal, waste detoxification, and decomposition. Many of these are not only responsible for sustaining the productive potential of our agricultural land and rural regions, but also contribute significantly to human health and wellbeing, and our overall ‘quality of life’ in urban areas.

The Sydney Water example clearly illustrates the connectivity and interdependencies between natural, rural and urban areas. Yet the importance of this broader context, in terms of regional sustainability, often goes unrecognised. For this reason, Mathis Wackernagel and William Rees of the University of British Columbia, developed the concept of the ‘ecological footprint’ - defined as the area of land that is needed to produce the natural resources a population consumes and to assimilate the wastes that they produce (Wackernagel and Rees 1996).

The aim of this approach is to highlight the societal dependence on ecosystem support. Results of these analyses in Australia reveal that the ecological footprint of the average Australian is around 6 hectares per capita, well above the global average of 1.8 hectares per capita (Simpson et al 2000). It is, therefore, quite clear that the impact of Australia's urban environments extends well beyond our city limits.

It is useful to discuss sustainability and ecosystem services at a regional level.

This is because regions are often defined by either land use or biogeographical similarity which, in many cases, renders them equivalent in scale to catchments - the level at which many of our natural resources are managed. However, in addition to the scientific convenience, there is also a growing trend among many design professionals to work at these larger scales as well (e.g. neighbourhood and community level planning and design).

The main purpose of this paper is to discuss both the nature and value of three broad groups of ecosystem services that are of particular relevance to many design professionals natural recovery services, environmental regulation services, and quality of life services. Ways in which design professionals may be able to utilise this knowledge to shape our rural and urban environments in a more sustainable way are suggested. Many of these suggestions are not new but, collectively, provide a highly integrated and novel design approach, through ‘smarter’ application of existing technology and knowledge.

2.0 NATURAL RECOVERY SERVICES

The quest for regional sustainability is under threat from a plethora of environmental problems, including the enhanced greenhouse effect, increasing pollution levels, reduction of water quality, dryland salinisation, and the contamination of food crops. Yet, despite the many negative environmental consequences of 200 years of European agricultural and industrial activity in Australia, there are now enormous opportunities for our design professionals to contribute to the reversal of this trend through the use of ecosystem design principles that capitalise on the natural recovery services provided by ecosystems.

2.1 Water purification

Freshwater is an extremely valuable commodity, particularly in Australia. Nearly all our freshwater resource is derived from rivers and aquifers, as most of our dams and lakes are created through river impoundments. A good barometer for the health of these freshwater resources is catchment health (see Walker and Reuter 1996).

This is because terrestrial and aquatic ecosystems are explicitly linked through the hydrological cycle and, in particular, through rainfall runoff and infiltration processes. Aquifers are buffered from degradation to some extent by their overlying soils and geology, but those that are close to the surface, with rapid modes of recharge, are often highly responsive to catchment health. Examples include the Gnangara Mound of Perth, Western Australia, and the limestone karst aquifers of the Mount Gambier region, South Australia.
Innovative design professionals have been utilising the water purification services of ecosystems for some time under the banner of ‘water sensitive planning’ and ‘stormwater management’.

The aim of these design approaches is to construct our built environment in a way that is analogous to the sustainable water management strategies of our natural ecosystems. The key underlying design principle is to capture, store, and utilise rainfall where it falls. This design approach can be more effective and less costly than the traditional design practice of creating smooth concrete-lined drains for rapid water transport off-site.

Instead, the ecological design focus is on minimising the amount of impervious surface cover as much as possible, as well as utilising vegetation buffers, soil infiltration, soil adsorption, and wetland processes to improve on-site water quality and management.

Dense ground covers, such as grass, are one of the most effective vegetation buffers. The use of trees and shrubs should be restricted to those that maintain or enhance ground cover vegetation. The primary aim of these buffers is to slow the runoff down so that water-borne pollutants, such as sediments and nutrients, can be filtered-out by both the structural influence of the vegetation and the process of soil infiltration. When combined with various swale and drain landform designs, vegetation buffer treatments provide enhanced stability and resistance to processes of soil and bank erosion. Soils themselves provide significant water purification services through the process of adsorption (immobilisation) of many nutrients and pesticides, which is vital for water quality in many of our aquifers.

Many large-scale projects are now incorporating combinations of grassed swales and constructed wetlands to improve water quality through a range of physical, chemical and biological processes. These projects are often typified by the provision of public open space, incorporating water purification services, aesthetics, and recreation opportunities. The Penrith Lakes Scheme in Western Sydney is a prime example, as is Charles Sturt University Thurgoona Campus, Albury (see BDP Environmental Design Guide: CAS 19).

A recent study has shown that the provision of adequate clean water to New York City by forests in the Catskill Mountains, was equivalent to a capital investment of US$6-8 billion and an annual $1-2 billion operating cost for a plant to carry out the same service. The City decided to maintain its water quality through the enhancement of ecosystem services, by purchasing small parcels of land, applying covenants on use of fertilisers in the catchment, and making a one-off investment of approximately $1 billion for upgrading local sewerage plants.

2.2 Atmospheric cleansing

Air quality is an important issue in most large cities, both throughout Australia and internationally. There is obviously a strong role for institutional reform and technological advancement to control point sources of pollution and remedy this situation, but there is also an essential role for plants. This is because plants, in particular trees due to their large leaf area and the volume they can occupy in the built environment, are able to reduce the levels of airborne pollutants, such as nitrogen dioxide, carbon monoxide, carbon dioxide, volatile organic carbons, sulphur dioxide and ozone, as well as filter and remove fine particulate matter from the atmosphere (Lyle 1999). Plants can also provide an important indirect contribution to air quality through the provision of shade and shelter services, which can reduce the energy required for heating and cooling buildings, however this is discussed separately.

The design professional can make an important contribution to air quality improvement through the selection of low energy design solutions that reduce our demand for fossil fuels. However, those that capitalise on the capacity of plants to cleanse the atmosphere can make another equally significant contribution.

Both indoor and outdoor air quality can be improved in this fashion, although the focus here is on the latter, particularly in areas such as densely developed city centres and industrial areas.
Plants provide one of the most critical of all ecosystem services - creating the oxygen we breathe by taking up carbon dioxide through the process of photosynthesis.

However, this oxygen production is also important for the dilution of atmospheric pollutants. For instance, the oxygen produced by roadside vegetation can assist in lowering carbon monoxide levels along heavy traffic routes (Hough 1995). Several overseas studies also indicate the value of this service - up to 85% of air pollution in a park can be filtered out by the cleansing ability of vegetation, and up to 70% in a tree lined street (Bolund and Hunhammar 1999).

By way of illustrating the value of the atmospheric cleansing services of plants, a recent study has estimated that the trees of the Chicago region removed approximately 5500 tonnes of air pollutants over a single year (McPherson et al 1997). The value of this service was estimated to be worth more than US$9 million.

Figure 1. The atmospheric cleansing services of vegetation along heavy traffic routes.
Reprinted from Design for Human Ecosystems, Lyle, JT, Page 206, Copyright 1999, with permission from Island Press.

While the results of some of these studies are impressive, it is important that they are tempered with some basic design principles and framed within an Australian context. Firstly, as with the design of windbreaks in rural areas, porosity of the vegetation is very important. Those plantings that are too dense may simply create an impermeable barrier and an increase in air turbulence, whereas less dense plantings will allow some through-flow of air, thereby facilitating the process of atmospheric cleansing.

However, it is important to recognise that some of the pollutants that collect on plant leaves can cause significant damage to the plant (Lyle 1999). This can be a problem for sensitive plants or plants that are located in areas with infrequent rainfall to wash the leaf surface, leading to the clogging of pores (stomata) by particles which effectively chokes the plant. In this regard, deciduous trees such as beech, ash, plane and elm could be incorporated into designs aimed at tackling serious air quality problems, as they will grow new leaves every year.

The autumn leaf fall in urban parks and streets could be collected for organic matter recycling via composting systems, to minimise adverse downstream effects of excessive organic matter on the urban stormwater system. The only problem with using deciduous trees is that there are considerable periods of time when they have no leaves at all, and thus are not providing any atmospheric cleansing services. An alternative approach would be to use certain native species such as eucalypts, which are non-deciduous, but continually replace their leaves on a regular basis - the average life for eucalyptus leaves is two years.

However, it is also important to recognise that eucalypts are a significant source of urban air pollution. For instance, research suggests that non-methane hydrocarbon emissions from biological sources, largely native vegetation, comprise 64% of total emissions in the Brisbane region and about 21% in the Sydney region. Nevertheless, there are a multitude of excellent reasons why this fact alone should not influence the conservation of existing native vegetation or the selection of native plants for new developments.

2.3 Decontamination and waste assimilation

As evidenced by the re-development of Homebush Bay, Sydney, increasing economic, environmental and political pressures are seeing many of Australia's contaminated land resources (i.e. brownfield sites) being scrutinised for their potential to be cleaned-up and redeveloped. The decision on whether to proceed with such activities should always depend on careful analysis of the various costs and benefits.

In this regard, recent developments in the area of biotechnology may help to reduce the clean-up cost of some sites and make redevelopment options more viable. With an estimated 60,000 to 100,000 contaminated sites in Australia and a clean-up cost in the vicinity of $5-8 billion (Davis 1999), the low cost options of these decontamination services is likely to be considerable.

Natural attenuation (self-cleansing) techniques are based on processes of ecosystems that include dilution, bacterial degradation, chemical reactions, and adsorption of contaminants onto soil. The major benefit of these approaches is that they provide in situ biological remediation, hence minimal physical disturbance of the soil, compared with the conventional practice of digging up and removing the contaminated soil.

These natural attenuation techniques are currently being utilised to remove toxic compounds in soils, especially crude oil and other petroleum products, phenols, fertilisers, herbicides and pesticides, agricultural chemicals, chlorinated solvents from industry, and preservatives such as creosote.

CSIRO research into natural attenuation processes is showing promising results, with gasoline constituents including benzene, being removed from groundwater over a period of hours to days (Davis 1999). Various other techniques are being devised that will ‘speed-up’ natural attenuation processes, such as the injection of air into contaminated soil to increase microbial degradation of petroleum hydrocarbons, such as diesel.
While these results are encouraging, it is essential to recognise that there may be many other instances or sites where these natural attenuation processes are ineffective, requiring substantial human intervention to remove the contaminants.

Nevertheless, it is important that design professionals are aware of the land decontamination services provided by ecosystems when considering the use of contaminated sites.

Design professionals should also consider incorporating greater natural capacity into the built environment for absorbing the common pollutants found in urban stormwater runoff.

This has been discussed to some extent with regard to water purification and atmospheric cleansing, however, requires more design focus on the provision of healthy soil/plant ecosystems throughout the landscape to recycle water and air.

There is also the potential to incorporate community gardening schemes into new developments or areas of urban renewal for the primary purposes of recycling organic waste material, such as leaf litter and suitable household organic matter, but also to provide human food and recreational opportunities.

3.0 ENVIRONMENTAL REGULATION SERVICES

Ecosystem services can play a significant role in regulating the environment in which we live. This role is likely to become increasingly important, as the enhanced greenhouse effect and various other environmental changes begin to impact detrimentally on our environment.

Ecosystem services, particularly those that act to stabilise the environment, confer a degree of resilience to these changes. For instance, plants help to control climate through the provision of shade and shelter, as well as contributing to noise reduction, particularly when planted in the form of a dense ‘windbreak’.

The impact of flooding in urban areas can also be significantly moderated by the ability of the plant/soil ecosystem to slow, absorb, and use water, not only in downstream wetlands, but also in upland forest and woodland remnants.

3.1 Climate amelioration

Climate amelioration services can be provided by either built solutions (e.g. pergolas) or living plants. The focus here is on the latter, whereby structurally complex plants such as trees and shrubs are important because of the influence they exert on local climate. During periods of hot weather, these types of plants are capable of significantly lowering air temperatures, through the shade they create when intercepting incoming solar radiation.

This natural shade is generally much cooler than that provided by built solutions, as plants do not store and re-radiate heat, instead, they contribute to further cooling through evaporation and transpiration from their leaves. The cooling service provided by carefully designed tree and shrub plantings has been found to reduce the consumption of energy for air-conditioning by 10 to 50%, depending on the level of building insulation (Lyle 1999).

Farmers are well aware of the productivity gains that can be derived from the shelter benefits of windbreaks during cold weather. However, this awareness appears to be far less advanced in the urban environment, despite evidence of urban benefits. A US study suggests that windbreak plantings to reduce heat loss from buildings can lower annual heating costs by 10 to 30% (Hough 1995). They also have a vital role in reducing wind tunnel effects.

Through the adoption of these climate amelioration services, it would seem that design professionals could have a profound effect on regional sustainability, primarily through reductions in energy consumption and greenhouse gas generation. Other papers within the BDP Environment Design Guide deal with this issue in more detail through various energy efficiency and passive solar design approaches (see GEN 12, GEN 35 and DES 32). As a general rule, design professionals should aim to maximise summer building performance through the provision of dense shade and the

Figure 2. Shade and cooling services provided by vegetation in the built environment.
Adapted from Atmospheric Environment, Vol 30, Golany, GS, Urban Design Morphology and Thermal Performance, p 463, Copyright 1996, with permission from Elsevier Science.

‘evaporative’ cooling of moist landscaping treatments. For maximum cooling, dense shade is required because sparse plantings or individual specimen trees are likely to provide ineffective shade. Winter solar gain should be enhanced by the use of deciduous trees on the northern aspect, as well as dense tree and shrub plantings in other locations to provide protection from cold winter winds.

Many of these ideas are already current design practice, but the benefit at a regional level is in the cost reductions and contribution to regional sustainability from enhancing the knowledge and uptake of these ecosystem services.

3.2 Noise reduction

Noise from traffic and other sources is a significant concern in many regions of Australia. The distance from the source of the noise is obviously a key determinant of the magnitude of the problem, but characteristics of the landscape such as landform type, surface cover and vegetation density are also other key components.

In Australia and other parts of the world, an increasingly popular solution to noise problems in residential areas that are adjacent to heavy traffic routes is to construct artificial noise barriers. There is obviously an important role for these built solutions, which can reduce noise by 10-15 dB(A), but given their high cost and negative impact on the visual landscape, other natural solutions should also be considered (Bolund and Hunhammar 1999).

One such solution is the use of vegetation, although there are many conflicting reports as to the extent by which vegetation can contribute to noise reduction. For instance, some suggest that a planting of dense shrubs 5m wide will reduce noise levels by 2 dB(A) and a 50m wide plantation by between 3-6 dB(A).

Others claim that 100m of dense vegetation may only reduce noise by 1-2 dB(A). Nevertheless, whatever the contribution, there is obviously some role for evergreen vegetation in dampening noise and shielding the visual intrusion of traffic. Design professionals should be aware of this role and the multiple benefits that can be derived from plants in these locations, such as water purification and atmospheric cleansing.

3.3 Flood mitigation

Many urban regions of Australia, not surprisingly, are made up of considerable built infrastructure, consisting largely of concrete and asphalt surfaces. These materials are essentially impervious to water flow, and thus result in substantial alterations to the regional hydrology more rainfall runoff and increased peak flood discharges (Bolund and Hunhammar 1999). The overall consequence is a higher probability of flooding in urban regions than rural regions, under similar rainfall events.

The main reason for this difference is the value that rural regions derive from the role of vegetation and soils in providing flood mitigation services. The way they do this is essentially the same as that described for water purification services - ground cover vegetation slows the flow of water and provides greater opportunity for infiltration into the soil. There is also a considerable amount of water that is taken up by plants and released to the air through evaporation and transpiration.

The flood mitigation services of vegetation and soil will be most valued in those regions that regularly experience high intensity rainfall events. In these regions, for new land development and for upgrading old infrastructure, conventional storm water drainage systems could be supplemented with the provision of a variety of soil and vegetation buffers. These could include various grassed swale and drain landform designs, temporary detention ponds, and constructed wetlands. Overall, the primary aim should be to reduce the amount of impervious surface cover within urbanised catchments and maximise the surface area of vegetation (preferably with native species).

A study in the Chesapeake Bay Region of the USA found that the stormwater retention capacity of their urban forest cover in 1997 was worth US$4.68 billion. This figure was calculated by multiplying the cost of constructing equivalent built infrastructure by the total volume of avoided storage.

4.0 QUALITY OF LIFE SERVICES

There are many stresses associated with modern day life in Australia, not only in the major towns and cities where there is a hectic pace of life, but also in the country where many agricultural commodity prices are depressed and there are serious social issues associated with high unemployment and youth suicide rates. Many of these stresses often manifest themselves in the population's health or state of well-being.

This connection has prompted several researchers to examine the beneficial effects of the natural environment on our quality of life (Alberti 1999). The results of some of these studies suggest that various services provided by natural ecosystems provide a positive influence on human health, emotional satisfaction and our general sense of well-being.

4.1 Human health

There is considerable scientific evidence that human activity is causing major environmental change such as diminishing biodiversity, major soil degradation, and global warming. But what is more worrying is the impact that these changes are having on major global ecosystem services, such as those responsible for stabilising the environment.

Many consider that there is a strong correlation between the disruption of these services and human health (Alberti 1999). They argue that as the ability of the global environment to sustain human activity declines, we are likely to see an increase in human health problems, such as foetal abnormalities, more infectious disease, and prevalence of skin cancer (Rapport 1998).

Design professionals can contribute to the maintenance of human health by fostering those ecosystem services that act to stabilise the environment - climate regulation, natural pest control, water purification, atmospheric cleansing, and ‘no waste’ recycling services. Thus, the broad task of the design professional is to conduct activities in a manner that will maximise ecological integrity, such as incorporating design approaches that integrate ecosystem functioning and biodiversity conservation. In other words, incorporating an ‘ecological design’ ethos into professional practice whereby potential environmental problems are removed from infrastructure developments at the start of the design process (van der Ryn and Cowan 1996).

4.2 Emotional satisfaction and well-being

The majority of Australians spend most of their time in human constructed environments such as major towns and cities. There is evidence from the USA that many people living in these urban environments feel their lives are lacking the quality they desire (Lyle 1999). Researchers have credited part of this sense of unfulfillment to separation from the natural environment.

Other studies documented by Alberti (1999) reveal that contact with natural features of the urban environment can both reduce stress and promote well-being in hospitals, prisons, the work place, and residential settings. For instance, it has been shown that physical contact with plants through gardening, particularly in low income areas, can lead to much greater community pride, increased social interactions, and less vandalism (Lyle 1999). Researchers attribute this to the sense of both peacefulness and tranquillity that gardening produces.

Emotional satisfaction and well-being are also enhanced by other life fulfilling services, such as the provision of aesthetic beauty, cultural, intellectual, and spiritual inspiration, sense of place, existence value, scientific discovery, and serenity. These particular services are bound up with culture, meaning and values, and the overall relationship between people and the environment.

They should all be serious design considerations because they are defining features of our Australian sense of identity, our culture and our values.

When shaping the built environment, it is important that design professionals recognise the emotional satisfaction and general sense of well-being that the natural environment can provide to urban residents. Conscious effort should be made to ensure that built-up areas are highly integrated and connected with the natural environment, and that there are plenty of opportunities for the urban residents to both play and rest. Where these connections are not already apparent, ecological design and planning processes should be used to undertake environmentally responsive urban renewal.

This could involve the establishment of native vegetation elements in the landscape, possibly to attract native wildlife or to foster human interactions with nature, through to small strategic exotic tree plantings for amenity, or even the notion of an 'edible landscape' whereby fruit and nut trees are a design element.
Design professionals should also take particular regard of existing vegetation both natural and cultural.

Appropriately designed developments will benefit from the conservation, habitat amenity, shade and historical attributes, which may already exist on development sites. Some, but not all of these aspects, will need to be considered under a variety of Commonwealth and State legislation. However, innovative designers will incorporate all these important aspects in their overall design from the outset, and hence should not only satisfy conservation and legislative requirements, but will also provide for unique and highly sought after habitats for people.

5.0 DISCUSSION AND IMPLICATIONS

The focus of this paper so far has been on developing an ecological awareness, or ‘ecological literacy’, with regard to the processes responsible for delivering important ecosystem services to our built environment. There are numerous other ecosystem services that have not been mentioned, but which sustain the productive potential of Australia’s land and the supply of human foods and resources.

This is not because they are less important, but because their relevance to design professions is not so immediate.

An outline for understanding the way in which the natural environment can interact with the built environment has been presented. The next step is for design professionals to explore ways in which they can use this knowledge to expand, modify, or even reshape elements of the natural environment to accommodate human purposes in a more sustainable way than traditional built environment solutions.

A key component of this design shift requires greater recognition of our ‘ecological footprint’ or, in other words, the natural resources that are being appropriated from distant regions to support current urban activities. But more importantly, acknowledging that the way in which we manage and organise our built environment is the key determinant of the level of environmental pressure we are placing on rural and regional Australia.

For this reason, there is an urgent need to move beyond simply conservation of nature in urban environments, towards more holistic approaches that focus on reducing our ‘ecological footprint’ and increasing well-being. These approaches, such as the trend towards urban consolidation and green development (see Wilson et al 1998) could significantly improve Australia’s urban environmental performance and thereby enhance rural and regional sustainability, provided they are well-informed through ecological design.

It is important to recognise, however, that undertaking development in an environmentally responsive fashion does not need to be an altruistic pursuit, but rather, can result in significant short and long term commercial benefits. In other words, the application of ecological thinking to planning and design can be good for business (Wilson et al 1998).

One of the first modern-era development projects to successfully create an environmentally sensitive, human-scale residential community is Michael Corbett's 240-unit Village Homes subdivision in Davis California, completed in 1981. Through the adoption of ‘whole system thinking’ approaches, Corbett was able to incorporate innovative ecological design elements that not only provided the solution to one problem, but also often solved several others at the same time.

For instance, the use of narrower streets at Village Homes, helped to reduce the amount of storm water runoff, enabling simple infiltration swales and on-site detention basins to handle storm water. However, in addition, these narrower streets also left more room for trees, and the multiple benefits that they provide, as well as providing traffic-calming benefits and contributing to a stronger sense of community. The end-result was the avoidance of unnecessary storm water infrastructure spending, leaving more money available to invest in houses, neighbourhood support systems and landscapes.

Hence, it is the multiple benefits that accrue from this type of thinking that should be the real attraction to design professionals.

6.0 CONCLUSION

Ecosystem services are the basic processes provided by our ecosystems that support life itself. They are often not well understood and their economic values are largely unrecognised, but they provide the critical underpinning of rural and regional sustainability and, hence, our current urban way of life.

If Australia and its inhabitants are to have a viable future, we urgently need to re-examine the consequences of our present patterns of human activity, with a view towards seeking those activities that are more compatible with the integrity of ecosystem services.

Design professionals have an important role in this regard, as they are responsible for shaping our built environment.

The challenge is to inject this ecological way of thinking into mainstream design practice.

REFERENCES

Alberti, M, 1999, ‘Urban patterns and environmental performance: what do we know?’, Journal of Planning Education and Research, vol 19, pp 151-163.

Bolund, P & Hunhammar, S, 1999, Ecosystem services in urban areas, Ecological Economics, vol 29, pp 293
301.

Davis, G, 1999, ‘Natural attenuation: nature's remedy for contamination?’, Bogong, vol 20, no 3, pp 17-19. Golany, GS, 1996, ‘Urban design morphology and thermal performance’, Atmospheric Environment, vol 30,
no 3, pp 455-465. Hough, M, 1995, Cities and natural processes, Routledge, London.

Lyle, JT, 1999, Design for human ecosystems, Island Press, Washington, USA. McPherson, EG, Nowak, D, Heisler, G, Grimmond, S, Souch, C, Grant, R, & Rowntree, R, 1997, ‘Quantifying urban forest structure, function and value: the Chicago Urban Forest Climate Project’, Urban Ecosystems, vol 1, pp 49-61.

Newman, P, Birrell, B, Holmes, D, Mathers, C, Newton, P, Oakley, G, O’Connor, A, Walker, B, Spessa, A, & Tait, D, 1996, ‘Chapter 3: Human Settlements’, in Australia: State of the Environment 1996, ed, State of the Environment Advisory Council, CSIRO Publishing, Melbourne.

Rapport, DJ, 1998, ‘Ecosystem health: an integrative science’, in Ecosystem health, ed, Rapport, DJ, Costanza, R, Epstein, PR, Gaudet, C, & Levins, R, Blackwell Science, Malden.

Simpson, RW, Petroeschevsky, A, & Lowe, I, 2000, 'An ecological footprint analysis for Australia', Australian Journal of Environmental Management, vol 7, pp 11-16.

Stein, PL, 2000, ‘The great Sydney water crisis of 1998’, Water, Air and Soil Pollution, vol 123, pp 419
436.

van der Ryn, S & Cowan, S, 1996, Ecological Design, Island Press, Washington. Wackernagel, M & Rees, W, 1996, Our ecological footprint, reducing human impact on the earth, New Society Publishers, British Columbia. Walker, J & Reuter, DJ, 1996, Indicators of catchment health: a technical perspective, CSIRO Publishing, Melbourne.

Wilson, A, Uncapher, JL, McManigal, L, Lovins, LH, Cureton, M, & Browning, WD, 1998, Green Development: Integrating Ecology and Real Estate. John Wiley & Sons, Inc, Toronto.