The following section comprises a review of the main concepts underlying the study, including the concepts of Green Infrastructure, ecosystem services and biodiversity, and the links between ecosystem services and human health and well-being.
2.2 Definition of key concepts
The following section provides definitions of some of the key terms included in this report. More detailed definitions may also be included in the relevant sections.
Health. The most widely referenced definition of health is that of the World Health Organization which defines health as ‘a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity’ (World Health Organization, 1946).
Well-being comprises not just the benefits gained from psychological and physical health, but is also related to specific aspects of well-being such as favourable thoughts and feelings, satisfaction with life, ability to be self-sufficient and proactive, possessing a sense of happiness, and a positive evaluation of life in a general sense (Diener et al., 1999).
Nature. (Maller et al., 2006) defines nature as referring to ‘any single element of the natural environment (such as plants, animals, soil, water or air), and includes domestic and companion animals as well as cultivated pot plants’. Researchers also subdivide nature into different categories, for example the Health Council of the Netherlands (Health Council of the Netherlands, 2004) nominates the following:
- Urban nature: nature in an urban setting (e.g. gardens, parks)
- Agricultural nature: primarily agricultural landscape with small, dedicated patches of nature
- Natural forests: nature in ‘woodlands’ where management emphasizes more authentic vegetation
- Wild nature: nature in an environment that develops spontaneously and can be maintained with minimal management (e.g. natural rivers, woodlands etc.)
The concept of ‘nature’ is in one sense a human construct, reflecting societal and individual value systems. Discussing the ‘ethics of sustainability’ (Thompson, 2000) reviews the different human attitudes to nature and environmental ethics. He identifies the following typologies or positions within environmental ethics:
- Anthropocentric position
- Ego-centric. Self-interest
- Homo-centric. The greatest good for the greatest number. We are responsible for stewardship of nature for human use and enjoyment
- Non-anthropocentric position
- Bio-centric. Members of the biotic community have moral standing
- Eco-centric. Ecosystems and/or the biosphere have moral standing. We have a duty of care to the whole environment
Aldo Leopold’s (1948) Land Ethic is an early statement of the eco-centric position, as is McHarg’s (1979) philosophy of Design with Nature, and James Lovelock’s 1979 Gaia hypothesis. In his book Man's Responsibility for Nature Australian philosopher John Passmore (1974) argued that there is urgent need to change our attitudes to the environment, and that humans cannot continue the unconstrained exploitation of the biosphere. However, his case for environmental stewardship rested on an anthropocentric viewpoint, of valuing nature in terms of what it contributes to human well-being rather than attributing an intrinsic value to nature, as advocated by the ‘deep ecology’ movement.
The Urban forest
The urban forest has been defined as ‘the sum of all publicly and privately owned trees within an urban area, including street trees, trees on private property, and remnant stands of native vegetation’ (Nowak et al., 2001; Miller, 2007). The urban forest is an integral part of the ‘urban ecosystem’ in which a wide range of physical and human elements interact to influence the quality of urban life. The concept of urban forestry is widely adopted in the United States and Europe (Konijnendijk, 2008), and more locally a number of councils have developed Urban Forest Strategies. Notably the City of Melbourne has recently completed a major strategy for the sustainable management of its urban forest (City of Melbourne, 2011). Brisbane’s urban forest strategic planning, targets, policies and programs are focused on optimising the multiple benefits of the extensive and diverse public and private tree cover whilst balancing the risks, costs and other priorities of a growing city (Brisbane City, 2013a).
National Urban Forest Alliance
The National Urban Forest Alliance (NUFA, 2013) has recently been formed to ‘promote a thriving, sustainable and diverse Australian Urban Forest that creates a contiguous and healthy ecosystem that is valued and cared for by all Australians as an essential environmental, economic, and community asset’. Its goals are to ‘develop, partner trial and implement systems, programmes, communications, guidelines, landscaping and infrastructure to grow the Australian Urban Forest’. Values of the Urban Forest include:
1. Reducing greenhouse emissions by sheltering nearby buildings from sun and wind
2. Reducing the urban heat island effect in a time of climate change to improve liveability and comfort
3. Improving air quality for our atmosphere and water quality for our waterways and bays
4. Sequestering carbon from the atmosphere to help prevent climate change
5. Increasing habitat to support biodiversity
6. Providing food such as fruits, nuts, spices
7. Increasing the life of infrastructure through weather protection
8. Improving the visual amenity of streetscapes and neighbourhoods
9. Increasing real estate value of properties with tree lined streets or in close proximity to green landscaped areas
10.Improving the health of residents by encouraging them to walk and be more active
Current Stakeholders include but are not limited to:
• Arboriculture Australia
• Brisbane City Council
• Nursery & Garden Industry Australia
• Parramatta City Council
• Australian Landscape Industry
• Campbelltown City Council
• Parks & Leisure Australia
• Darwin City Council
• Melbourne City Council
• Launceston City Council
• Sydney City Council
• ENSPEC Pty Ltd
2.3 Green Infrastructure
The following section summarizes the different definitions of Green Infrastructure (GI), the scope of GI practices, and the key GI concepts of multifunctionality and connectivity.
‘Green Infrastructure is a term that is appearing more and more frequently in land conservation and development discussions across the country and around the world. Green infrastructure means different things to different people depending on the context in which it is used. For example, some people refer to trees in urban areas as green infrastructure because of the ‘green’ benefits they provide, while others use Green Infrastructure to refer to engineered structures (such water treatment facilities or green roofs) that are designed to be environmentally friendly’ (Benedict and McMahon, 2002) p.5.
Three main perspectives on Green Infrastructure have been identified in the literature review.
a) Ecosystem services approach. In this approach Green Infrastructure emerges from a global perspective in terms of the ecosystem services (ESS) delivered by nature and natural cycles (Costanza et al., 1997; Millennium Ecosystem Assessment, 2003). These natural cycles operate globally, but can also be retained, restored and maintained within cities to produce local benefits. Historically this perspective is closely linked to the development of the concepts of sustainable development and urban ecology (Spirn, 1984; Hough, 2004).
b) Linked green spaces approach. In this approach Green Infrastructure emphasizes the importance of retaining and linking green spaces, nature corridors and drainage networks in cities to enhance ecosystem functioning (Benedict and McMahon, 2002). In this sense the network of Green Infrastructure is seen as analogous to the network of conventional engineering infrastructure underlying the functioning of a city. Green Infrastructure networks can provide a ‘green’ framework for more sustainable urban development.
c) Green engineering approach. In this approach Green Infrastructure is viewed as a specialized form of engineering infrastructure, replacing conventional engineering structures with ‘green’ elements which can perform ecosystem service functions, such as waste management or building energy efficiency (Margolis and Robinson, 2007). For example the City of Sydney labels energy tri-generation and a decentralized water networks as ‘Green Infrastructure’ responses to climate change (Kinesis, 2012; City of Sydney, 2012a). This green engineering approach can include the use of green roofs and living walls to cool buildings, or the use of vegetation to purify stormwater runoff in Water Sensitive Urban Design installations.
Green Infrastructure can take a number of forms, and can provide a wide range of what are known as Ecosystem Services (ESS). Some of the ecosystem services that can be provided by Green Infrastructure include the following:
- Human health and well-being
- Social and psychological
- Visual and aesthetic
- Human health and well-being
- Commercial vitality
- Increased property values
- Value of ecosystem services
- Climatic modification
- Temperature reduction
- Wind speed modification
- Temperature reduction
- Climate change mitigation
- Carbon sequestration and storage
- Avoided emissions (reduced energy use)
- Air quality improvement
- Pollutant removal
- Avoided emissions
- Water cycle modification
- Flow control and flood reduction
- Canopy interception
- Soil infiltration and storage
- Water quality improvement
- Flow control and flood reduction
- Soil improvements
- Soil stabilization
- Increased permeability
- Waste decomposition and nutrient cycling
- Species diversity
- Habitat and corridors
- Food production
- Productive agricultural land
- Urban agriculture
- Climatic modification
Definition of infrastructure
‘the basic physical and organisational structures and facilities (e.g. buildings, roads, power supplies) needed for the operation of a society or enterprise’: the social and economic infrastructure of a country. Source: Oxford Dictionary.
Infrastructure systems are essential to the functioning of the modern high density city. Traditional ‘grey infrastructure’ comprises the engineered network of roads and services, which deliver a range of goods and services to the population of a city. These infrastructure systems require major capital investment to build and maintain, and are generally single use occupiers of large areas of urban land (Wolf, 2003).
|‘Green Infrastructure is the network of natural and semi-natural areas, features and green spaces in rural and urban, and terrestrial, freshwater, coastal and marine areas, which together enhance ecosystem health and resilience, contribute to biodiversity conservation and benefit human populations through the maintenance and enhancement of ecosystem services. Green Infrastructure can be strengthened through strategic and co-ordinated initiatives that focus on maintaining, restoring, improving and connecting existing areas and features, as well as creating new areas and features’. Source: Naumann et al. (2011a).|
Green Infrastructure is an emerging concept, based on the realization that natural systems can deliver a range of engineering and human services to the city, known as ‘ecosystem services’ (Bolund and Hunhammar, 1999; Nowak and Dwyer, 2007; Pataki et al., 2011). The concept is thought to have originated in the United States in the 1990s, emphasizing the ‘life support’ functions provided by the natural environment. Green Infrastructure can provide a range of tangible environmental services, including stormwater management, air quality improvement, carbon sequestration, and mitigation of urban heat island effects. However the Green Infrastructure concept also includes the more anthropocentric functions of the natural environment, including those related to human social, recreational and cultural values. For example Green Infrastructure has been described as ‘an interconnected network of green space that conserves natural ecosystem values and functions, and provides associated benefits to human populations’ (Benedict and McMahon, 2002).
‘The term ‘Green Infrastructure’ describes the network of natural landscape assets which underpin the economic, socio-cultural and environmental functionality of our cities and towns-i.e. the green spaces and water systems which intersperse, connect and provide vital life support for humans and other species within our urban environments’.
‘Individual components of this environmental network are sometimes referred to as ‘Green Infrastructure assets’, and these occur across a range of landscape scales—from residential gardens to local parks and housing estates, streetscapes and highway verges, services and communications corridors, waterways and regional recreation areas etc.’. Source: Australian Institute of Landscape Architects Green Infrastructure Report (2012).
‘GI is a successfully tested tool for providing ecological, economic and social benefits through natural solutions. It helps us to understand the value of the benefits that nature provides to human society and to mobilise investments to sustain and enhance them. It also helps avoid relying on infrastructure that is expensive to build when nature can often provide cheaper, more durable solutions. Many of these create local job opportunities. Green Infrastructure is based on the principle that protecting and enhancing nature and natural processes, and the many benefits human society gets from nature, are consciously integrated into spatial planning and territorial development. Compared to single-purpose, grey infrastructure, GI has many benefits. It is not a constraint on territorial development but promotes natural solutions if they are the best option. It can sometimes offer an alternative, or be complementary, to standard grey solutions’.
‘Many definitions of GI have been developed. It is therefore difficult to cover all aspects in one short paragraph. The following working definition will however be used for the purposes of this Communication’.
‘GI: a strategically planned network of natural and semi-natural areas with other environmental features designed and managed to deliver a wide range of ecosystem services. It incorporates green spaces (or blue if aquatic ecosystems are concerned) and other physical features in terrestrial (including coastal) and marine areas. On land, GI is present in rural and urban settings’. Source: European Commission (2013) p.2.
The following elements can contribute to a city’s Green Infrastructure network (Oxigen, 2011):
- Public Parks and Gardens, including urban parks, open space reserves, cemeteries and formal gardens
- Greenways, including river and creek corridors, cycleways and routes along major transport (road, rail and tram) corridors
- Residential and other streets, comprising street verges and associated open space pockets
- Sports and recreational facilities, including ovals, golf courses, school and other institutional playing fields, and other major parks
- Private/Semi Private Gardens, including shared (communal) spaces around apartment buildings, backyards, balconies, roof gardens and community (productive) gardens
- Green roofs and walls, including roof gardens and living walls
- Squares and Plazas, including both public and private courtyards and forecourts
- Natural green space, including national parks and nature reserves, wetlands and coastal margins
- Utility areas, including quarries, airports, and large institutional and manufacturing sites. This category also includes unused land reserved for future use
- Agricultural and other productive land, including vineyards, market gardens, orchards and farms
Green Infrastructure can perform multiple roles in urban areas, for example recreation, biodiversity, cultural identity, environmental quality and biological solutions to technical problems (Sandstrom, 2002; see also Figure 2). Green Infrastructure can also be seen as comprising all of the natural, semi-natural and artificial networks of multifunctional ecological systems within, around and between urban areas, at all spatial scales (Sandstrom, 2002; Tzoulas et al., 2007). Importantly, Green Infrastructure can deliver multiple benefits from the valuable urban space it occupies, compared with traditional single purpose engineering infrastructure (Wolf, 2003). It is this multifunctionality of Green Infrastructure that differentiates it from its ‘grey’ counterparts, which tend to be designed to perform one function, such as transport or drainage, without contributing to the broader environmental, social and economic context (Naumann et al., 2011a).
Figure 2: Victoria Park Sydney, grassed detention basin/community park. Source: M. Ely.
The European Commission’s report on The Multifunctionality of Green Infrastructure (European Commission, 2012) provides a comprehensive list of the Green Infrastructure features that contribute to four types of Green Infrastructure functions or roles:
- Protecting ecosystem state and biodiversity
- Improving ecosystem functioning and promoting ecosystem services
- Promoting societal well-being and health
- Supporting the development of a green economy and sustainable land and water management
The following section lists the Green Infrastructure ‘features’ that can contribute to each of these roles.
Protecting ecosystem state and biodiversity
Green Infrastructure features that contribute to the role of protecting ecosystem state and biodiversity include the following, as adapted from (European Commission, 2012):
- Nature-rich areas, which function as core areas and hubs for GI
- Wildlife and natural areas, which can be wilderness areas or managed areas
- Areas of high value for biodiversity and ecosystem health outside protected areas, such as floodplain areas and wetlands
- Ecological corridors used by wildlife to allow movement between areas. In general, three types of corridor can be identified:
- Linear corridors comprising long strips of vegetation, such as roadside vegetation, strips of remnant bushland, and the vegetation growing along rivers and streams
- Stepping stone corridors, which are a series of small, non-connected habitats
- Landscape corridors of diverse, uninterrupted landscape elements (e.g. riparian zones)
- Greenways and greenbelts, where greenways are corridors of undeveloped land and greenbelts are belts of parks or rural land surrounding or within a city
- Eco ducts or green bridges, structures that connect two areas of nature and allow wildlife to travel across significant barriers, such as roads
- Fish ladders, fishways or fish passes are a series of pools at the side of a waterway, enabling freshwater organisms to swim upstream, around a dam or other obstruction
- Ecological stepping-stones are a series of usually small, unconnected habitats that allow wildlife to move from one to another
- Ecological buffer areas comprise zones that surround areas of ecological value, aimed at minimizing the impacts of adjacent land uses or activities
- Restored landscapes and ecosystems. These can be ‘passive’ where the damaging activity has ceased, or ‘active’, involving targeted actions, such as revegetation of brownfield land. Examples of habitats that may be restored include native grasslands, rivers and wetlands
- Urban elements, such as parks, gardens, open spaces, housing allotments, waterways, green roofs and living walls
- Agricultural land that is managed sustainably, in terms of protecting biodiversity and ecosystems
Improving ecosystem functioning and promoting ecosystem services
Green Infrastructure features that perform the role ofimproving ecosystem functioning and promoting ecosystem services include the following, adapted from (European Commission, 2012), and are additional to those listed in the previous section.
- Areas of high nature value outside protected areas, such as floodplain areas, riparian zones, wetlands, natural forests and semi-natural grasslands and sustainably managed agricultural lands, which can deliver ecosystem services such as water regulation, carbon storage and coastal protection
- Restored habitats that have specific functions and/or species in mind, for example, to increase breeding or nesting for those species or to enhance the carbon and water cycles of those areas
- Water bodies and wetlands, including constructed wetlands for water quality improvement
- Urban trees, vegetation and soils which can remove CO2 from the air and also sequester carbon
- Vegetated landscapes to absorb and harvest water and convey it either to a storage facility for reuse or discharge it into downstream drainage systems. These include:
- green vegetated roofs or ecoroofs
- rain/infiltration gardens and trenches
- vegetated swales which generally consist of a drainage course with gently sloped sides and filled with vegetation
- Permeable pavements made from porous materials, such as porous asphalt or eco-paving systems
- Water Sensitive Urban Design (WSUD) also known as Sustainable Urban Drainage Systems (SUDS) in the UK and Low Impact Development in the US which integrates storm water management into the design of urban landscapes. This may include some of the GI features listed above, such as green roofs, permeable pavements, bio-swales and the preservation of natural landscapes and forested areas
Promoting societal health and wellbeing
Green Infrastructure features that perform the role of promoting societal health and well being include the following, adapted from (European Commission, 2012), and are additional to those listed in the previous sections.
- Public parks, pathways, playing fields, cycle paths and jogging tracks that encourage outdoor activity and promote physical health
- Urban vegetation, i.e. trees, green roofs and private gardens that regulate air quality and help reduce the ‘urban heat island’ effect
- Wetlands, grassed areas and urban forests that reduce the risk of flooding and degradation of aquatic ecosystems
- Public parks, streets and urban spaces that enhance community attachment, social cohesion and a sense of environmental responsibility
- Green spaces that attract tourism and investment and improve employment and income potential
2.3.5 Green Infrastructure networks
The other distinguishing feature of Green Infrastructure is that of ‘connectivity’ and ‘value adding’ by linking existing green assets and resources.
In the US in 1999 the Green Infrastructure Working Group developed the following definition of Green Infrastructure.
‘Green Infrastructure is our nation’s natural life support system - an interconnected network of waterways, wetlands, woodlands, wildlife habitats, and other natural areas; greenways, parks and other conservation lands; working farms, ranches and forests; and wilderness and other open spaces that support native species, maintain natural ecological processes, sustain air and water resources and contribute to the health and quality of life for America’s communities and people (Benedict and McMahon, 2002).
This ‘network’ approach to Green Infrastructure comprises a system of ‘hubs’ (for example parks, reserves and agricultural land) and ‘linkages’ (for example habitat corridors, greenways and river systems), and is based on the concept that ‘green’ resources are more effective if linked together rather than fragmented. This concept has its roots in planning and conservation ideas dating back over a century, and includes two important concepts (Benedict and McMahon, 2002):
- Linking parks and other green spaces for the benefit of people.
- Preserving and linking natural areas to benefit biodiversity and counter habitat fragmentation.
Linking of open spaces for public benefits
In his work in public parks in the late eighteenth and early nineteenth centuries, United States landscape architect Frederick Law Olmsted believed that ‘no single park, no matter how large and how well designed, would provide the citizens with the beneficial influences of nature.’ Instead parks need ‘to be linked to one another and to surrounding residential neighbourhoods’ (Little, 1989).
Olmsted also believed that ‘A connected system of parks and parkways is manifestly far more complete and useful than a series of isolated parks’. This idea of linking parks for the benefit of people, with a focus on recreation, multi-use trails and public health, subsequently evolved into the modern ‘greenways’ movement in the United States, and the ‘greenbelt’ movement in the UK.
Linking to counter habitat fragmentation
Wildlife biologists and ecologists have long recognized that the most effective way to conserve native plants, wildlife and ecosystems is to create interconnected conservation systems which counter the trend towards habitat fragmentation (Benedict and McMahon, 2002). Protecting and restoring the connections between parks and other natural assets is now a key concept in both the science of conservation biology and the practice of ecosystem management. Historically the concept was popularized in the development of the discipline of landscape ecology, which addresses ecological structure and function at the landscape scale, and has since been adopted as a land use planning tool at a range of scales (Forman and Godron, 1986). This approach was also incorporated into the practice of landscape architecture and landscape planning by Ian McHarg in the 1970s in his concept of ecological landscape design, which is based on recognizing and mapping natural processes in the landscape and using these as determinants in the design process (McHarg, 1979).
The Green Infrastructure network approach envisages a network of ’green’ and ‘blue’ elements providing the framework for more sustainable urban development (analogous to the grey infrastructure networks of pipes and roads that provide the framework of the modern city). (Benedict and McMahon, 2002) consider that this ‘greenprint’ approach should be based on the following set of guiding principles:
- Green Infrastructure should be the framework for conservation and development.
- Design and plan Green Infrastructure before development.
- Linkage is key.
- Green Infrastructure functions across multiple jurisdictions and at different scales.
- Green Infrastructure is a critical public investment.
- Green Infrastructure is grounded in sound science and land use planning theories and practices.
2.4 Ecosystem Services (ESS)
The concept of ecosystem services (ESS) is fundamental to an understanding of Green Infrastructure, and is applicable at range of scales from the global to the local.
2.4.1 Global perspective
|Ecosystem services are the benefits provided to humans through the transformations of resources (or environmental assets, including land, water, vegetation and atmosphere) into a flow of essential goods and services e.g. clean air, water, and food. Source: Costanza, d’Arge et al. (1997)|
The concept of ecosystem services has been gradually developing over the last century as a way of recognising the dependence of human societies on nature-based systems. (Daily, 1997) defines ecosystem services as ‘… the conditions and processes by which natural ecosystems, and the species that make them up, sustain and fulfil human life'. A growing awareness developed in the 1990s that healthy ecosystems provide goods and services that benefit humans and other life. Work by noted scientists such as Ehrlich, Daily, Kennedy, Matson, and Costanza helped to support this groundswell of environmental awareness (Daily, 1997).
‘Concern has been growing over the last half century as evidence of decline in the world’s ecosystems grows and ecologists, economists and other social scientists debate the underlying socio-economic causes. More than ever before in human history, people living in cities have lost their awareness of their reliance on natural ecosystems for food, regulation of the atmosphere and climate, purification of water, provision of building and raw materials for industry, protection from pests, diseases and extreme weather, and for cultural, spiritual and intellectual stimulation and fulfilment’. Source: Cork (nd).
In response to these concerns the United Nations commissioned a global study called the Millennium Ecosystem Assessment, which was conducted by an international consortium of governments, non-profit organisations, universities, and businesses. The group’s report, published in 2005, stated that ‘ecosystems are critical to human well-being, to our health, our prosperity, our security, and to our social and cultural identity’ (Millennium Ecosystem Assessment, 2005b). Today the link between environmental well-being, human well-being, and economic prosperity continues to be part of mainstream political conversation (Mainka et al., 2008).
Global value of ecosystem services
In 1997 Costanza and others estimated the global value of ecosystem services expressed in monetary units to be in the range of $15 - $47 Trillion/yr., (average $33 Trillion/yr. in 1995 $US or $46 Trillion/yr. in 2007 $US). This estimate was revisited in 2012 (de Groot et al., 2012). Using the same methods as the 1997 paper, the total global value estimated for 2011 from the new data was $125 Trillion/yr., assuming both unit values and biome areas changed, $145 Trillion/yr. assuming only unit values changed and $41.6 Trillion/yr. assuming only areas changed (all in 2007 $US). Based on this the loss of ecosystem services from 1997 to 2011 was estimated at $4.3 Trillion/yr. using 1997 unit values and $20.2 Trillion/yr. using 2011 unit values.
Source: Costanza, d’Arge et al. (1997).
2.4.2 Scope of Ecosystem Services
Ecosystem services are the benefits people obtain from ecosystems. These include provisioning, regulating, and cultural services that directly affect people and supporting services needed to maintain the other services’.
Source: Millennium Ecosystem Assessment (2003) p.57.
As shown in Figure 3, the Millennium Ecosystem Assessment provided a framework for categorizing the societal benefits of ecosystems into four different groupings (Millennium Ecosystem Assessment, 2003):
- Provisioning services (which provide food and materials)
- Cultural services (which provide aesthetic and psychological benefits)
- Regulating services (which moderate environmental conditions and quality)
- Supporting services (which underlie all ecosystem services)
Figure 3: Ecosystem Services. Source: ‘Ecosystems and human well-being: a framework for assessment’, Millennium Ecosystem Assessment (2003) p.57.
The following section summarizes the scope of these ecosystem services as identified by the Millennium Ecosystem Assessment.
Provisioning Services are the products obtained from ecosystems, including:
- Food and fibre.This includes the vast range of food products derived from plants, animals, and microbes, as well as materials such as wood, jute, hemp, silk, and many other products derived from ecosystems
- Fuel. Wood, dung, and other biological materials serve as sources of energy
- Genetic resources. This includes the genes and genetic information used for animal and plant breeding and biotechnology
- Biochemicals, natural medicines, and pharmaceuticals. Many medicines, biocides, food additives such as alginates, and biological materials are derived from ecosystems
- Ornamental resources. Animal products, such as skins and shells, and flowers are used as ornaments, although the value of these resources is often culturally determined. This is an example of linkages between the categories of ecosystem services
- Fresh water. Fresh water is another example of linkages between categories, in this case, between provisioning and regulating services
These are the benefits obtained from the regulation of ecosystem processes. They are closely linked to many fundamental biogeochemical processes, which are the biological and chemical processes that cycle and transform carbon, nutrients (e.g. nitrogen and phosphorus), water, and other materials in the environment (Pataki et al., 2011). Regulating services include:
- Air quality maintenance.Ecosystems both contribute chemicals to and extract chemicals from the atmosphere, influencing many aspects of air quality
- Climate regulation. Ecosystems influence climate both locally and globally. For example, at a local scale, changes in land cover can affect both temperature and precipitation. At the global scale, ecosystems play an important role in climate by either sequestering or emitting greenhouse gases
- Water regulation. The timing and magnitude of runoff, flooding, and aquifer recharge can be strongly influenced by changes in land cover, including, in particular, alterations that change the water storage potential of the system, such as the conversion of wetlands or the replacement of forests with croplands or croplands with urban areas
- Erosion control. Vegetative cover plays an important role in soil retention and the prevention of landslides
- Water purification and waste treatment. Ecosystems can be a source of impurities in fresh water but also can help to filter out and decompose organic wastes introduced into inland waters and coastal and marine ecosystems
- Regulation of human diseases. Changes in ecosystems can directly change the abundance of human pathogens, such as cholera, and can alter the abundance of disease vectors, such as mosquitoes
- Biological control. Ecosystem changes affect the prevalence of crop and livestock pests and diseases
- Pollination.Ecosystem changes affect the distribution, abundance, and effectiveness of pollinators
- Storm protection.The presence of coastal ecosystems such as mangroves and coral reefs can dramatically reduce the damage caused by hurricanes or large waves
These are the nonmaterial benefits people obtain from ecosystems through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experiences, including:
- Cultural diversity.The diversity of ecosystems is one factor influencing the diversity of cultures
- Spiritual and religious values. Many religions attach spiritual and religious values to ecosystems or their components
- Knowledge systems (traditional and formal). Ecosystems influence the types of knowledge systems developed by different cultures
- Educational values. Ecosystems and their components and processes provide the basis for both formal and informal education in many societies
- Inspiration. Ecosystems provide a rich source of inspiration for art, folklore, national symbols, architecture, and advertising
- Aesthetic values.Many people find beauty or aesthetic value in various aspects of ecosystems, as reflected in the support for parks, “scenic drives,” and the selection of housing locations.
- Social relations.Ecosystems influence the types of social relations that are established in particular cultures. Fishing societies, for example, differ in many respects in their social relations from nomadic herding or agricultural societies
- Sense of place. Many people value the ‘sense of place’ that is associated with recognized features of their environment, including aspects of the ecosystem
- Cultural heritage values.Many societies place high value on the maintenance of either historically important landscapes (‘cultural landscapes’) or culturally significant species
- Recreation and ecotourism. People often choose where to spend their leisure time based in part on the characteristics of the natural or cultivated landscapes in a particular area
Cultural services are closely linked to human values and behaviour, as well as to human institutions and patterns of social, economic, and political organization. Therefore perceptions of cultural services are more likely to differ among individuals and communities than, say, perceptions of the importance of provisioning or regulating services such as food production or clean air.
Supporting services are defined as those services that are necessary for the production of all other ecosystem services. They differ from provisioning, regulating, and cultural services in that their impacts on people are either indirect or occur over a very long time, while changes in the other services have more direct and short-term impacts (Millennium Ecosystem Assessment, 2003). Some examples of supporting services are:
- Primary production
- Climate regulation
- Production of atmospheric oxygen
- Soil formation and retention.
- Nutrient cycling
- Water cycling
- Provisioning of habitat
Maintaining biodiversity and ecosystem health is considered to be essential if ecosystems are to continue to deliver ecosystem services to cities and urban areas. One definition of biodiversity is ‘the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems’ (Millennium Ecosystem Assessment, 2005) p.18. There are many measures of biodiversity. Species richness (the number of species in a given area) is a single but important metric often used to measure biodiversity, but it must be integrated with other metrics for a full understanding of the biodiversity of a place.
According to the (Millennium Ecosystem Assessment, 2005a), ‘Biodiversity is the foundation of ecosystem services to which human well-being is intimately linked’…breathable air, potable water, fertile soils, productive lands, bountiful seas, the equitable climate of Earth’s recent history, and other ecosystem services are manifestations of the workings of life. It follows that large-scale human influences over this biota have tremendous impacts on human well-being’ (Millennium Ecosystem Assessment, 2005) p.18.
Figure 4 summarizes the many links between biodiversity and ecosystem services.
Figure 4: Biodiversity and Ecosystem Services. Source: Ecosystems and Human Well-being: Biodiversity Synthesis, Millennium Ecosystem Assessment (2005) p.28.
2.6 Natural Cycles
A number of natural cycles also underlie ecosystem health and the delivery of ecosystem services.
Natural cycles process water, carbon, nitrogen and minerals through the living and non-living worlds, and between the land, oceans and atmosphere (Campbell et al., 2006; Cross and Spencer, 2009). These natural cycles are part of the supporting services necessary for the production of all other ecosystem services. Urbanization can dramatically modify these natural cycles and their ability to produce ecosystem services. A sustainable approach to design should attempt to integrate these natural cycles into the urban environment (Ely, 2010). For example urbanization dramatically modifies the natural water cycle through the use of impervious surfaces and engineered drainage systems. A key objective of WSUD is to restore or replicate the natural water cycle in urban areas.
2.6.1 The Water Cycle
The hydrological cycle recycles and purifies water(see Figure 5). It includes seven main processes: evaporation; transpiration (water lost from plants, having been taken up by their roots); condensation; precipitation; infiltration (water movement into the soil); percolation (water movement through the soil into groundwater); and runoff. The water cycle is driven by energy and gravity, however plants play a crucial role in terms of modifying rainfall inflows, water movement into and through the soil, and water outflows through evapotranspiration, surface runoff and subsurface drainage (Xiao et al., 2006; Cross and Spencer, 2009). A key aim of Water Sensitive Urban Design (WSUD) is to better integrate the natural water cycle into the urban environment, at a range of scales (Argue, 2004).
Figure 5: The Natural Hydrologic Cycle. Source: The Case for Sustainable Landscapes, Sustainable Sites Initiative (2009) p.29.
2.6.2 The Carbon Cycle
Plants play a critical role in the carbon cycle, photosynthesizing organic carbon compounds from atmospheric carbon, water and energy from sunlight, and by releasing oxygen during the same process. Plants are consumed by animals and the organic compounds are re-synthesized in other forms. Plants and animals release carbon dioxide into the atmosphere during respiration by oxidizing these organic compounds. The carbon cycle is completed as plants and animals produce waste products and die, with dead organic matter being decomposed, releasing carbon as carbon dioxide. Carbon is stored in trees and forests and can act as carbon sinks as long as they are actively growing, and reach a steady state as carbon dioxide uptake is matched by carbon dioxide released from death and decay (Nowak et al., 2007). Urbanization can significantly modify the carbon cycle, notable in the increased emission of CO2 and its impacts on global climate change.
Figure 6: The Carbon Cycle. Source: The Case for Sustainable Landscapes, Sustainable Sites Initiative (2009) p.30.
2.6.3 The Nitrogen Cycle
In the nitrogen cycle,(see Figure 7) small amounts of N2 are converted into forms that can be used by plants, primarily by nitrogen fixing bacteria in the root nodules of some plants (Craul, 1992). Decomposition of organic wastes releases nitrogen in the form of ammonia. Under aerobic conditions it is oxidized by nitrifiers to a nitrate. Plants usually take up nitrogen in the form of nitrate in order to synthesize proteins. Humans also add nitrogen to the system through the use of nitrogen fertilizers, and disposal of wastewater into waterways. Urbanisation can impact on the nutrient cycle with impervious surfaces interrupting nutrient exchange with the soil, and with increasingly polluted urban runoff impacting on the health of aquatic ecosystems.
Figure 7: The Nitrogen Cycle. Source: The Case for Sustainable Landscapes, Sustainable Sites Initiative (2009) p.30.
2.7 Human health and well-being
From an anthropocentric viewpoint, biodiversity and ecosystem services are fundamental to human health and well-being. There have been many formulations and definitions of human well-being (Alkire, 2002). Researchers generally agree that it includes basic material needs for a good life, the experience of freedom, health, personal security, and good social relations. Together, these provide the conditions for physical, social, psychological, and spiritual fulfilment (Millennium Ecosystem Assessment, 2003). A research study entitled Voices of the Poor: Crying Out for Change identified five key dimensions of human well-being (Narayan et al., 2000):
- The necessary material for a good life (including secure and adequate livelihoods, income and assets, enough food at all times, shelter, furniture, clothing, and access to goods).
- Health (including being strong, feeling well, and having a healthy physical environment).
- Good social relations (including social cohesion, mutual respect, good gender and family relations, and the ability to help others and provide for children).
- Security (including secure access to natural and other resources, safety of person and possessions, and living in a predictable and controllable environment with security from natural and human-made disasters).
- Freedom and choice (including having control over what happens and being able to achieve what a person values doing or being).
2.7.2 Links between ecosystem services and human well-being
In the ‘urban ecosystem’ a wide range of physical and human elements interact to influence the quality of urban life (Nowak et al., 2001; Nowak, 2010). People are an integral part of the urban ecosystem, and ecosystem services are indispensable to human health and well-being.
Figure 8: Ecosystems and human health and well-being. Source: Sustainable Sites Initiative (2009).
Understanding the causal links between the environment and human health and well-being is complex are they are often indirect, displaced in space and time, and dependent on a number of modifying forces. As discussed earlier, the Millennium Assessment identified five main aspects of human well-being: materials, health, social relations, security, and freedom and choice (Millennium Ecosystem Assessment, 2005a).
Figure 9 illustrates the ways in which one of these aspects, human health, is affected directly and indirectly by ecosystems, and also by changes to other aspects of well-being. Deficiencies in any one aspect of human well-being (materials, social relations, security, freedom and choice) can have health impacts, and health can also influence these other aspects of human well-being.
Figure 9: Interrelationship between ecosystem services, aspects of human well-being and human health. Source: Ecosystems and human well-being: health synthesis. Millennium Ecosystem Assessment (2005a) p.14.
Figure 9 shows how the provisioning functions of ecosystems provide goods and services that support human well-being, and shortages of these can impact on health and well-being. The regulating functions of ecosystems affect human well-being in a number of ways, including the availability of clean air, fresh water, reduced risk of flooding or drought, stabilization of local and regional climates, and checks and balances on the range and transmission of certain diseases. ‘Without these regulatory functions, the varied populations of human and animal life are inconceivable’(Millennium Ecosystem Assessment, 2003). Ecosystems also influence human well-being through the provision of cultural services, for example scenic landscapes. These ecosystem attributes influence the aesthetic, recreational, educational, cultural, and spiritual aspects of human life. Changes to ecosystems, through pollution, depletion, and extinction, can therefore have negative impacts on cultural life and human experience. Finally, supporting services are essential for sustaining each of the other three ecosystem service areas. Figure 10 provides a more detailed illustration of the complex interactions between ecosystem services and human well-being.
Figure 10: Categories of ecosystem services. Source: Ecosystems and human well-being: health synthesis. Millennium Ecosystem Assessment (2005a) p.14.
Sustainability and the related concepts of ‘sustainable development’ and ‘sustainable design’ are closely linked to the concept of Green Infrastructure.
2.8.1 Sustainable design
The term ‘sustainability’ has emerged in the past decades as a broad set of principles addressing social, economic and environmental development at almost any scale (Watson, 2007). However, despite its widespread use, the term does not have an agreed definition, and to some extent has become a ‘buzzword’ for marketing a range of ‘green’ products (Thompson and Sorvig, 2008). At its core, it refers to the ability to manage a system (social, economic or environmental) so as to perpetuate it indefinitely without compromising the ability to continue to do so in the future (Johnson and Hill, 2002). The current widespread use of the term has evolved from the concept of ‘sustainable development’. This originated in the Stockholm Conference on the Human Environment in 1972, appeared in the World Conservation Strategy in 1980, and came of age in the 1987 Brundtland Commission Report, Our Common Future (Thompson, 2000). The often quoted definition used in the latter was development that ‘…meets the needs of the present without diminishing the ability of future generations to meet their own needs’(WCED, 1990). The scope of the term was later enlarged at the United Nations 1992 Earth Summit in Rio de Janiro to address global development policies including issues of poverty, resource imbalance and inequalities in global development. The Rio Earth Summit's Agenda 21 produced a well-known set of sustainability principles adopted by many governments, including local government authorities in Australia.
Sustainability as a concept, however, has much earlier roots than the relatively recent concept of sustainable development. Its environmental and ethical basis originates from ecology, as evident in the writings of Aldo Leopold in his 1948 classic The Land Ethic, which proposed an ecological approach to land and landscapes (Leopold, 1948). The term was also applied to forestry and agriculture in the 1970s to describe management policies which maintain natural resource capacity (Benson and Roe, 2000). The concept of ‘sustained yield’ is used by foresters and others (including fishery and water resource managers) to define a harvestable surplus that can be indefinitely maintained, without reducing the productive capital. However, sustainable yield can be difficult to quantify because of the dynamic nature of ecological systems and the role of other non-harvesting factors which affect both the natural capital and its productivity.
A related concept is that of permaculture, an approach to designing human settlements and agricultural systems that mimic natural ecologies. Permaculture was developed by Australians Bill Mollison and David Holmgren in the 1970s and aims to achieve ‘permanent’, self-sufficient and stable agricultural and cultural systems, through training in a core set of design principles (Mollison, 1988). While originating as an agro-ecological design theory, permaculture has grown into a wider value system for sustainable human settlements (Holmgren, 2002).
The design professions have also embraced the concept of sustainability, with the roots of ‘sustainable design’ in the ‘ecological design’ movement, which emerged in the United Kingdom in the mid-twentieth century in the work of Brenda Colvin, Sylvia Crowe and Simon Hackett, and in the United States in the work of Ian McHarg (Benson and Roe, 2000). In 1979, Ian McHarg published his seminal book on ecological design at the regional scale, Design with Nature, (McHarg 1979), and in 1984 Anne Whiston Spirn applied ecological principles to the city in The Granite Garden (Spirn, 1984). In the 1980s writers such as John Lyle suggested that sustainability alone was not sufficient, and that designed ecosystems should be ‘regenerative’ and capable of renewing energy and materials, rather than ‘degenerative’ (Lyle, 1994). Other writers have addressed the relationship between sustainable landscapes, landscape aesthetics and community preferences (Thayer, 1989; Thayer, 1994).
2.8.2 Sustainable landscapes
The term ‘sustainable landscapes’ has been adopted more recently by the landscape architecture profession. In their book, Sustainable Landscape Design and Construction (first published in 2000 and revised in 2008), (Thompson and Sorvig, 2000) suggest that sustainable landscapes:
‘Contribute to human well-being and at the same time are in harmony with the natural environment. They do not deplete or damage other ecosystems. While human activity will have altered native patterns, a sustainable landscape will work with native conditions in its structure and functions. Valuable resources-water, nutrients, soil etcetera, and energy will be conserved, diversity of species will be maintained or increased.’
(Perry, 1995) has proposed a number of goals to develop and maintain sustainable landscapes. Similar goals are proposed by (Thompson and Sorvig, 2008). Such goals and principles typically include: local contextual design; selection of plants suited to local conditions; use of non-invasive plant species; reduced resource inputs of energy and materials; water conservation; enhanced biodiversity and habitat creation; avoidance of harmful chemicals; and productive use of gardens for food production. The Sustainable Landscapes Project at the Botanic Gardens of Adelaide in South Australia is a local collaboration between various government agencies, aimed at promoting sustainable landscape design and management (Sustainable Landscapes Project, 2012). A sustainable landscape is defined as:
‘a healthy and resilient landscape that will endure over the long term without the need for high input of scarce resources such as water. The natural functions and processes of the landscape are able to maintain it into the future’.
The Sustainable Landscapes Project defines eight criteria for sustainable landscapes:
- Design to suit local environmental conditions
- Use of low water use plants
- Use of non-weedy plants
- Water conservation measures
- Habitat creation
- Minimal chemical use
- Low non-renewable energy consumption
- Use of local and sustainable products
In the United States the Sustainable Sites Initiative (SITES™) is an interdisciplinary effort by the American Society of Landscape Architects, the Lady Bird Johnson Wildflower Center at The University of Texas at Austin and the United States Botanic Garden to create voluntary national guidelines and performance benchmarks for sustainable landscape design, construction and maintenance practices (Sustainable Sites Initiative, 2009).
A common goal is for landscapes’ …that conserve, recycle, and reuse resources to achieve optimal levels of sustainability’ (Perry, 1995). A useful way to consider the sustainable use of resources, such as water, materials, and energy, is to consider designed landscapes as functioning systems with inputs, outputs and internal cycling. Unsustainable systems tend to be ‘open’ with high resource inputs, minimal internal recycling, and high outputs of waste and energy. More sustainable systems will be more ‘closed’, with reduced inputs of materials and energy, a high level of internal recycling, and reduced waste outputs (Dunnett and Clayden, 2000).
2.8.3 Sustainable urban forestry
Concepts of sustainable forest management can also be applied to the urban forest (Wiersum, 1995; Clark et al., 1997; Dwyer et al., 2003). Sustainable urban forests can be defined as:
‘The naturally occurring and planted trees in cities which are managed to provide the inhabitants with a continuing level of economic, social, environmental and ecological benefits today and into the future’ (Clark et al., 1997).
Definitions of sustainable urban forestry emphasize the role of the people who manage and use the urban forest. Sustainable management of the urban forest involves an understanding of its diversity, dynamic nature, and connectedness to a range of human activities (Dwyer et al., 2003). Urban forests need to be managed to increase the net benefits they generate, and management systems are required that allow trees to flourish and maximize their benefits, while minimizing their impacts on the urban environment (McPherson, 1995). It is generally agreed that a sustainable urban forest will produce long-term net benefits associated with a relatively stable tree population and canopy cover (Miller, 2007). A sustainable urban forest, therefore, will exhibit: species and age diversity; a large percentage of healthy trees adapted to local conditions; and native forest as one component of canopy cover. In terms of species diversity, however, it should be noted that stability of tree populations will depend on the extent that the selected species are adapted to local conditions, and not just the number of species planted (Richards, 1993).
AILA (2012). "Adapting to Climate Change: Green Infrastructure." Retrieved 11/10/2012, from http://www.aila.org.au/greeninfrastructure/docs/AILA_green%20infrastructure.pdf.
Alkire, S. (2002). "Dimensions of human development." World Development 30 (2): 181–205.
Argue, J. R. (2004). Water Sensitive Urban Design: Basic Procedures for 'Source Control' of Stormwater. Adelaide, University of South Australia.
Benedict, M. A. and E. T. McMahon (2002). "Green infrastructure: smart conservation for the 21st century." Renewable Resources Journal 20 (3): 12-17.
Benson, J. F. and M. H. Roe, Eds. (2000). Landscape and Sustainability. London and New York, Spon Press.
Bolund, P. and S. Hunhammar (1999). "Ecosystem services in urban areas." Ecological economics 29: 293-301.
Brisbane City (2013a). State of Australian Cities 2013 - Brisbane Urban Forest Contribution, Brisbane City Council.
Campbell, N. A., J. B. Reece, et al. (2006). Biology. Frenchs Forest, N.S.W., Pearsons Education Australia.
City of Melbourne (2011). Urban Forest Strategy: Making a great city greener 2102-2032. Melbourne, Vic.: 53pp.
City of Sydney (2012a). Decentralised Water Master Plan 2012–2030, City of Sydney.
Clark, J. R., N. P. Matheny, et al. (1997). "A model of urban forest sustainability." Journal of Arboriculture 23 (1): 17-30.
Cork, S. J. (nd). The nature and value of ecosysyem services in Australia., CSIRO Sustainable Ecosystems.
Costanza, R., R. d’Arge, et al. (1997). "The value of the world’s ecosystem services and natural capital." Nature 387: 253–260.
Craul, P. J. (1992). Urban Soils in Landscape Design. New York, John Wiley & Sons, Inc.
Cross, R. and R. Spencer (2009). Sustainable Gardens. Collingwood, Vic., CSIRO Publishing.
Daily, G. E. (1997). Nature's Services - Societal Dependence on Natural Ecosystems Island Press, Washington.
de Groot, R., L. Brander, et al. (2012). "Global estimates of the value of ecosystems and their services in monetary units." Ecosystem Services 1: 50-61.
Diener, E., E. Suh, et al. (1999). "Subjective well-being:three decades of progress’." Psychological Bulletin 125 (2): 276-302.
Dunnett, N. and A. Clayden (2000). Resources:The raw materials of landscape. Landscape and Sustainability. London, Spon Press.
Dwyer, J. F., D. J. Nowak, et al. (2003). "Sustaining urban forests." Journal of Arboriculture 29 (1): 49-55.
Ely, M. E. (2010). Integrating trees into the design of the city. School of Architecture, Landscape Architecture and Urban Design. Adelaide, University of Adelaide. PhD: 464 pp.
European Commission (2012). The Multifunctionality of Green Infrastructure. Science for Environment Policy. In-depth Reports, European Commission’s Directorate-General Environment.
European Commission (2013). Green Infrastructure (GI): Enhancing Europe’s Natural Capital. Communication From the Commission to the European Parliament, The Council, The European Economic And Social Committee and the Committee Of The Regions. Brussels European Commission.
Forman, R. T. T. and M. Godron (1986). Landscape Ecology. New York., John Wiley and Sons.
Health Council of the Netherlands (2004). Nature and Health:The influence of nature on social, psychological and physical wellbeing The Hague, Health Council of the Netherlands and Dutch Advisory Council for Research on Spatial Planning Nature and the Environment.
Holmgren, D. (2002). Permaculture: Principles and pathways beyond sustainability. Hepburn, Victoria, Holmgren Design Services.
Hough, M. (2004). Cities and Natural Processes: a basis for sustainability. London, Routledge.
Johnson, B. R. and K. Hill, Eds. (2002). Ecology and Design: frameworks for learning. Washington, DC, Island Press.
Kinesis (2012). Decentralised Energy Master Plan: Trigeneration 2010–2030, City of Sydney.
Konijnendijk, C. C. (2008). The Forest and the City: The cultural landscape of urban woodland, Springer Science + Business Media.
Leopold, A. (1948). A Sand County Almanac. New York, Oxford University Press.
Little, C. E. (1989). Greenways for America. Baltimore and London.. The Johns Hopkins University Press..
Lovelock, J. (1979). Gaia: A New Look at Life on Earth Oxford University Press.
Lyle , J. T. (1994). Regenerative Design for Sustainable Development. New York, Wiley.
Mainka, S. A., J. A. McNeely, et al. (2008). "Depending on Nature: Ecosystem Services for Human Livelihoods." Environment and Behavior 50 (2).
Maller, C., M. Townsend, et al. (2006). "Healthy nature healthy people:‘contact with nature’as an upstream health promotion intervention for populations." Health Promotion International 21 (1): 45.
Margolis, L. and A. l. Robinson (2007). Living Systems. Basel, Birkhauser.
McHarg, I. L. (1979). Design with Nature. Philadelphia, Pennsylvania, Natural History Press.
McPherson, E. G. (1995). Net benefits of healthy and productive urban forests. Urban Forest Landscapes:Integrating Multidisciplinary Perspectives. G. A. Bradley, University of Washington Press.
Millennium Ecosystem Assessment (2003). Ecosystems and human well-being: a framework for assessment Washington, DC, Island Press.
Millennium Ecosystem Assessment (2005). Ecosystems and human well-being: Biodiversity synthesis. Washington, DC, World Resources Institute.
Millennium Ecosystem Assessment (2005a). Ecosystems and human well-being : health synthesis. Washington, DC, World Resources Institute.
Miller, R. W. (2007). Urban Forestry: Planning and Managing Urban Greenspaces. Long Grove,ILL., Waveland Press,Inc.
Mollison, B. (1988). Permaculture: A designer's manual. Tyalgum, N.S.W Tagari Publications.
Narayan, D., P. Chambers, et al. (2000). Voices of the Poor: Crying Out for Change. New York, Oxford University Press.
Naumann, S., D. McKenna, et al. (2011a). Design, implementation and cost elements of Green Infrastructure projects. Final report Brussels, European Commission.
Nowak, D. J. (2010). Sustaining America's urban trees and forests. General Technical Report NRS-62, U.S. Dept. of Agriculture, Forest Service, Northern Research Station: 27 pp.
Nowak, D. J. and J. F. Dwyer (2007). Understanding the benefits and costs of urban forest ecosystems. Urban and Community Forestry in the Northeast. J. Kruser. Newtown Square, PA., U.S.D.A. Forest Service, North Eastern Research Station,: 25-46.
Nowak, D. J., R. Hoehn, et al. (2007). "Oxygen production by trees in the United States." Journal of Arboriculture and Urban Forestry 33 (3): 220-226.
Nowak, D. J., M. H. Noble, et al. (2001). "Assessing the U.S. urban forest resource." Journal of Forestry 99 (3): 37-42.
NUFA (2013). "National Urban Forest Alliance (NUFA)." Retrieved 6 June 2013, from http://www.nufa.com.au/.
Oxigen (2011). Green Infrastructure Working Paper. Adelaide, Botanic Gardens of Adelaide.
Passmore, J. (1974). Man's Responsibility for Nature: Ecological Problems and Western Traditions. New York, Charles Scribner's Sons.
Pataki, D. E., M. M. Carreiro, et al. (2011). "Coupling biogeochemical cycles in urban environments: ecosystem services, green solutions, and misconceptions." Frontiers in Ecology 9 (1): 27–36.
Perry, R. C. (1995). Sustainability in landscaping. Urban Forest Landscapes: Integrating Multidisciplinary Perspectives. G. A. Bradley. Seattle and Washington, University of Washington Press: 175-179.
Richards, N. A. (1993). "Reasonable guidelines for street tree diversity." Journal of Arboriculture19 (6): 344-350.
Sandstrom, U. G. (2002). "Green Infrastructure planning in urban Sweden " Planning Practice & Research 17 (4): 373-385.
Spirn, A. W. (1984). The Granite Garden. New York, Basic Books.
Sustainable Landscapes Project (2012). "Sustainable Landscapes." Retrieved 18/09/2012, 2012, from http://www.environment.sa.gov.au/botanicgardens/learn/sustainable_landscapes_project.
Sustainable Sites Initiative (2009). The Case for Sustainable Landscapes, American Society of Landscape Architects, Lady Bird Johnson Wildflower Center at The University of Texas at Austin, United States Botanic Garden.
Thayer , R. L. (1989). "The Experience of Sustainable Landscapes." Landscape Journal 8 (2): 101-110.
Thayer , R. L. (1994). Gray World,Green Heart:Technology,Nature and Sustainable Landscape. New York, John Wiley.
Thompson, I. H. (2000). The Ethics of Sustainability. Landscape and Sustainability. London, Spon Press.
Thompson, I. H. and K. Sorvig (2008). Sustainable Landscape Construction: A guide to green building outdoors. 2nd. edition. Washington D.C., Island Press.
Thompson, J. W. and K. Sorvig (2000). Sustainable Landscape Construction:A guide to green building outdoors. Washington D.C., Island Press.
Tzoulas, K., K. Korpela, et al. (2007). "Promoting ecosystem and human health in urban areas using GreenInfrastructure: A literature review." Landscape and Urban Planning 81 (3): 167–178.
Watson, D. (2007). Sustainable design. Time-Saver Standards for Urban Design. D. Watson, McGraw-Hill Professional Publishing.
WCED (1990). Our common future (The Brundtland Report), World Commission on Environment and Development.
Wiersum, K. F. (1995). "200 years of sustainability in forestry: Lessons from history." Journal of Environmental Management 19 (3): 321-329.
Wolf, K. L. (2003). Ergonomics of the City: Green Infrastructure and Social Benefits. Engineering Green: Proceedings of the 2003 National Urban Forest Conference, Washington D.C.
World Health Organization (1946). Preamble to the constitution of the WHO as adopted by the International Health Conference, New York, 19-22 June 1946; signed on 22 July 1946 by the representative of 61 States. Records of the WHO, no. 2,. WHO: 100.
Xiao, Q., E. G. McPherson, et al. (2006). "Hydrologic processes at the urban residential scale." Hydrological Processes 21 (16): 2174 - 2188.