By Adrian McGregor, McGregor Coxall
FAVOURITES – 7 October 2009 –
“The so-called global economy was not a permanent institution, but a set of transient circumstances peculiar to a time, the Indian Summer of the fossil fuel era”.
– James Kunstler, The Long Emergency: surviving the converging catastrophes of the twenty-first century (2005).
Stone, bronze, and iron have defined the key technological ages of our civilisations and as a technocentric race we like to think that we are now living in the age of silicon. Truth is, the defining material of the last 150 years is undoubtedly oil. We are in the midst of the great oil age and cheap crude is the remarkable energy source that has driven the hyper-growth of our modern economies and cities.
The problem with this incredible period of urban population growth is that it will leave an unprecedented legacy of social and environmental crises for coming generations. With the imminent decline of oil reserves coupled to rising demand and an ever-increasing risk of the onset of a global anoxic oceanic event (when the world’s oceans become oxygen-depleted) driven by climate change, we need to make a major shift in city planning to enable pathways for positive adaptation.
The biocity is a theoretical urban design and planning model that proposes that cities be conceptualised as complex constructed ecosystems. By moving away from entrenched anthropocentric attitudes that divorce humans from their environment, the biocity concept unlocks impediments in achieving a whole-of-system regenerative design approach for cities.
Converging crises: peak oil and greenhouse gases
The wonder of oil is that it delivers 100 times more energy than it takes to extract it from the ground. No other energy source comes close to this and oil is cheaper than bottled water. The average Australian uses about 7.5 litres per day4 while an American uses about 10 litres of oil per day on food, travel and goods.5 The world is currently using about 31 billion barrels of oil a year, leaving about 75 years of endowment remaining.6 [figure 1]
Many researchers postulate it is unlikely the reserves will last this long as the remaining oil will be difficult to access, while the energy required for extraction will eventually surpass the stored energy of the fuel. At this time oil will become obsolete.[figure 2] As the renowned economic and environmental theorist James Kunstler warns in his book The Long Emergency, there is a grave danger of catastrophic geopolitical and economic systems failure as nations fight for the remaining cheap oil.
Only in the past 20 years have we really understood how oil formed. Oil is essentially a mix of hydrocarbons, molecules that contain only hydrogen and carbon, the stuff of life. Oil is refined to make fuels, bitumen and the chemicals that make up many of the products that we use daily.[figure 3] All our carbon was created when the planet was created and the atoms are now recycled in systems akin to the water and nitrogen cycles.[figure 4] There are approximately a trillion tonnes of carbon in living organisms and much more buried in rocks and geology underground.
One hundred and sixty million years ago in the mid-Jurassic dinosaurs roamed a super-heated earth. The planet was about half land and half water with two major land masses separated by the Rheic Ocean, an equatorial seascape. Australia was yet to be separated from Gondwanna and the oceans and atmosphere were loaded with CO2. Over time phytoplankton absorbed the CO2 and converted it via photosynthesis into oxygen and organic carbon that sank to the sea floor. Much of the oceans were anoxic and devoid of oxygen. This watery dead zone had a floor of organic debris that decomposed into a mud that eventually became petroleum source rock. Heat and pressure converted the rock into sweet crude.
It was not until the 1860s that oil went into commercial production following an oil rush begun by completion of the first commercially viable oil well in Pennsylvania in 1859 by Edwin Drake. [Figure 5] Before that coal had fuelled the industrial revolution of the 18th and early 19th century. In the late 19th century commercialised US oil began to fill the growing demand for kerosene lamps used as a replacement for whale oil lamps. Demand boomed and 40 years later the automobile appeared. In a little over 150 years we have used up half the world’s reserve of crude that took 160 million years to create.
CO2 is the climate balancer in the atmosphere.
By releasing the carbon molecule back into the atmosphere we are putting ourselves on a course for the Jurassic, back to a time of global anoxic oceanic events, the time of the super-greenhouse. An ice-free world where tropical storms swept across the planet, rotten-egg gas from anoxic oceans blew across the beaches and few species survived. The planet has a cycle of these events but we are turbocharging our way into the next one.
In environmental cycles growth is always balanced by decline. By burning the very liquid carbon that has catalysed our fossil fuel economies for the past 150 years we have liberated the carbon atom creating gaseous CO2 that is set to wreak environmental havoc through global warming. A 2006 study published in the scientific journal Conservation Biology warns that “global warming will result in catastrophic species loss across the planet.”7
Since the beginning of industrialisation the global mean temperature has risen by approximately 0.6 °C, faster than at any time in the last 1000 years.8 In research that has emerged over the past 30 years it seems likely that periods of global warming were coupled to oceanic anoxic events where temperatures soar, oceans become devoid of life and species diversity shrinks. These events appear to be triggered quickly and turn off quickly.
The Intergovernmental Panel on Climate Change (IPCC) has warned that we need to stabilise atmospheric CO2 at 450ppm to limit the global temperature rise at 2 degrees.9 This equates to a buffer of 400 billion tonnes of CO2. In the remaining oil [700 billion tonnes], coal [3500+ billion tonnes], and natural gas [500 billion tonnes] we have over 10 times this amount at our ready disposal.10 [Figure 6] Enough carbon to cook our planet many times over. The question is, can the world’s leaders, industries and citizens agree to stop burning carbon before we reach 400 billion tonnes and the chances of a super-greenhouse, global anoxic event is triggered? If not, we are likely to witness human devastation of an unseen intensity that will wreck our economies and ecosystems. The converging oil and climate emergencies of the 21st century are at our door.
All the great periods of civilisation eventually come to an end and this oil age is now running on half empty. Our blind faith in the free market economy is firmly rooted in our acceptance of contemporary economic science. According to Canadian environmental activist, Dr David Suzuki, the greatest evil facing the global environment, is the pseudo science of economics.11 Economic revenue is predicated on linear industrial processes of extraction, production and distribution. No value is assigned to the trees, minerals, water and human capital used in production or the resulting pollution. These raw materials and waste are conveniently factored out of the linear equation as externalities.
Economies that consume environmental matter at the highest rates sustain a high GDP per capita and are said to be advanced, while those that consume less are defined as developing. Our macroeconomies reward high levels of consumption of what Hawkins et al define as natural capital12 while the benefits are felt by a privileged few. The critical flaw of this system is that the faster it depletes our natural environment the more short-term financial reward it generates. Left unchecked this system is destined to consume itself. True science alerts us to the idea that the earths’ ecological carrying capacity will soon be exceeded. The effects of economic growth are being directly felt by the diminishment of our biodiversity. Never before have so many people been exposed to such a hyper scale of impending environmental and resources dilemmas.
Economics assumes that a rapacious consumption driven quest for growth can be endlessly sustained as though the Earths’ carrying capacity is limitless. Endless population growth is also required to expand the capacity of the system to consume. Over the past six months we have witnessed many of the world’s largest economies slide into major recession bringing the global free market economy to its knees. The powerful US banking system has crumbled and a collection of the world’s leaders are advocating an end to our acquiescence to the economic ideology of laissez-faire.
Co-incidentally global reserves of cheap oil recently peaked and oil prices for the remaining half are predicted to head ever-upwards. CSIRO forecasts that by 2018 the price of unleaded fuel will be about $8 per litre in Australia.13 Kunstler proposes that escalating oil costs will spell the end of globalisation and a meltdown in economies as manufacturing and shipping consumables becomes cost prohibitive.
Three of the five economic recessions between 1948 and 1970 and four of the five recessions since 1970 were preceded by big rises in oil prices.14 [Figure 7] As global oil supply diminishes, the geopolitical landscape will become less global and more introspective. Local concerns will take precedence over international affairs. Businesses dependent on the oil-based global supply chain will suffer deeply, sending financial markets and governments into a spin. It will be a long recession characterised by non-growth or shrinking economies. Our civilisation will again return to local economies reliant on surrounding agricultural land for food production and local renewable energy sources. These typological land use changes will require the creation of radically modified urban forms.
Climate change and oil depletion scenarios need long term, strategic, adaptation planning at a national and international level. Those nations that begin the shift from fossil fuels to renewable energy early will have urban systems in place that allow the continuance of political stability and democracy. In tandem with a focus on renewables a wholesale redesign of our economic system is required where the equations for wealth creation are rebuilt. This needs to be a bioeconomy model that mimics the cyclical throughputs of ecosystems, a model where natural and social capital is not free for the taking and the concept of pollution becomes obsolete.
“While technology keeps ahead of depletion, providing what appears to be ever cheaper metals, they only appear cheap because the stripped rain forest and the mountain of toxic tailings spilling into rivers, the impoverished villages and eroded indigenous cultures – all the consequences they leave in their wake – are not factored into the cost of production”. 11
The golden age of the city
Massive industrial age urban population growth has defined cities as the default containers of our civilisation. In 1800 only 2 per cent of the population lived in cities and today this has grown to 50 per cent. The role of cities in the past 200 years has changed dramatically. As Newman et al put it: “Cities are the defining ecological phenomenon of the twenty first century. From a minor part of the global economy one hundred years ago, they have become the principal engines of economic growth and the places where most of humanity dwells.”15 Occupying just 2 per cent of the planet’s surface, cities are responsible for more than two-thirds of global energy use and greenhouse gas emissions.
One of the major effects of the oil revolution has been hyper population growth. World population has ballooned from about 1 billion16 in our pre-industrialised, pre-oil era of 1850, to about 6.8 billion inhabitants today.17[figure 8] This growth has been primarily enabled through the extraction, distillation and ignition of cheap crude oil over the past 150 years. The total population of urban areas in 2050 is projected to double from 3.3 billion to 6.4 billion as world population reaches 9.2 billion.18 This means half of the Earth’s people already live in sprawling metropolises and in 40 years time only a third of people will live outside the city. Population growth and increases in the consumption patterns needed to sustain urban settlement correlate to a corresponding decline in species biodiversity since the beginning of industrialisation. Dr Edward Wilson, the Pulitzer Prize winning scholar and naturalist, estimates that some 27,000 species are lost every year.19
Alarmingly, one in three of today’s urbanites are slum dwellers. About 1 billion people now live in squalor in the fringing slums of our cities.20[Figure 9] Many slum dwellers move to the city after being displaced from their traditional homes due to the mechanisation of age-old farming practices bought about by the agribusinesses of the industrial revolution. These ubiquitous monocultures require vast inputs of petrochemical fertilisers and due to oil powered mechanisation need little labour to harvest. Consequently the horticultural skill base that human kind needs for feeding itself post oil is quickly disappearing.
The United Nations has forecast the number of megacities with more than 10 million residents will increase from 19 to 27 by mid-century as more agricultural workers move to cities.21 Urban areas are expected to absorb all population growth over this period while also assimilating rural population.22 We are in the golden age of the city, the greatest period ever of architectural exploration. The speed at which we have been able to construct the urban environment will not be repeated. It is estimated that in 2008 Dubai had approximately 25 per cent of the world’s construction cranes.[figure 10]
Oil has fundamentally shaped the forms of our modern cities. It has fuelled transport networks, building processes, telecommunications, sprawl and flows of finance. Fossil fuel planning has allowed development decisions to be made with cursory regard to renewable energy inputs or ecological impact. Cities have been able to survive beyond the support of their productive landscapes by creating long supply chain tentacles to all parts of the globe. It has been possible to live off the produce of far-removed places because oil-fuelled freight allows fresh foods to be transferred quickly and cheaply.[figure 11]
The concepts of ecological footprint and food miles are an emerging consumer concern in developed countries. In 2005 humanity used the equivalent of 1.3 Earths to support its consumption, based on the global biocapacity metric developed by the Global Footprint Network.32 Australia Australia has the fifth highest global footprint at almost 8 hectares per person.[figure 12] This overshoot cannot be sustained for long.
Some cities will find it easier to embrace post oil and climate change adaptation strategies because they possess a denser form and still may have local networks in place. Modern cities that have grown from an ancient core will be better positioned to adapt.
The time has come to realise that every single development decision has a far-reaching consequence across multiple systems in a city. No longer can we conceptually isolate the impact of singular economic, design and planning policy decisions on an urban system. The first step in generating a shift in thinking to address the converging emergencies is to acknowledge that cities are actually complex, constructed ecosystems. They should not be considered as separate from the other ecosystems that provide services to them. Rather, the linkages and synergies between the discrete systems should be the focus of our attention.
The biocity model
The biocity is a theoretical urban design and planning model that proposes cities be reconceptualised as interconnected ecosystems. By embracing an envirocentric agenda it opens the door to new paradigms for restorative urban programs through applying equal planning weight to cultural and environmental processes. Biocity respects the Earth’s abundance, enabling a recognition that humans are not divorced from natural systems.[figure 13] By looking to ecological systems for design inspiration, the model actively strives to go beyond the minimisation of development impact to produce regenerative legacies. By encouraging networks of human activity that are purposefully restorative, biocity aspires to nurture positive change, not just be less negative.
In moving away from entrenched anthropocentric attitudes that divorce humans and their creations from the environment, biocity unlocks impediments in achieving a whole of systems design approach. It is further defined by a purpose to understand the intricate relationships between urban and natural ecosystems so that informed design decisions can be implemented in a far more holistic and collaborative way than traditional silo based, reductionist practices allow. Biocity postulates cities to be vital ecosystems that are supported by a wide range of biotic and abiotic factors connected through a multitude of layered networks.[figure 14]
According to De Duve, ecosystems may be defined over a broad range of scales, from the community to the bioregional to the global, all “eventually closing into a single, gigantic web of formidable complexity”22[figure 15] Vasishth has described a city as a layered, overlapped, and nested arrangement of supra-systems, systems and subsystems, organised in scalar hierarchical arrangements.23 Biocity considers the city as the supra-system unit, and identifies twelve distinct systems that capture the major organisational networks of urban biotopes. Urban biotopes are defined by the extent of their ecological similarity. The systems are:
- Built form
When these 12 systems are interacting in a mutually supportive or symbiotic way, a healthy city with a compact ecological footprint is created.[figure 16] Energy is allogenic, originating outside the system and drives the transfer and consumption of physical and cultural inputs. The flows of energy enable the city to metabolise and support its various autogenic functions. British ecologist A.G. Tansley proposed the word “ecosystem” in 1935 and American Raymond L. Lindeman offered the now classic definition in 1942. This definition is based on the concept of energy flow through several trophic levels, ensuring the transformation or transmutation of material from one state to another.24
An expanded definition is required for urban ecosystems that amends the notion of food levels as the primary defining layers of the system.
Urban ecosystems could be said to be inherently unstable in time and space because they rely on human factors for their existence and are ecologically immature. Cities usually consume more food than they produce, and can be defined as heterotrophic ecosystems. Cities rely on services from other ecosystems for basic life support functions such as air and water purification, climate regulation, waste decomposition, and the provision of resources for human, plant and animal consumption.
Urban settlements with small ecofootprints are more adapted to their surrounding biome and may even boast a mutually supportive or symbiotic relationship with the other ecosystems that provide services to them. Cities that efficiently cycle matter require less energy input. According to Wendell Berry “the only sustainable city….is a city in balance with its countryside: a city, that is, that would live off the net ecological income of it’s supporting region, paying as it goes all its ecological and human debts.”25
Architect William McDonough shares the same design philosophy. “By fostering a deep connection between the built and natural landscapes and re-engaging people with their natural surroundings, we wish to design in accord with the laws that govern natural systems and processes, instilling an environmental intelligence that was once second nature.”26
Biocity was spawned from the growing global awareness that the forms of our contemporary cities are not sustainable. Low-density suburbia and its periurban paraphernalia are the material realisations of fossil fuel planning dreams. Isolation and social dysfunction2 are attributed to these failed urban forms. Postulations for the imminent end of surburbia3 are gaining momentum, spearheaded by authors, filmmakers and planners. Newman identifies “the need to counter the trend toward increasing globaliszation of city economies by focusing on the local and bioregional scales at which feedback loops can operate more effectively, and where consumption and production can be better matched to bioregional capacities.”15
The tragedy for the human race is that planning practices are not radically shifting in response to repeated scientific warnings on the effects of global warming from the IPCC and other think tanks. Australian planning dogma and infrastructure practices are riddled with outmoded post industrial ideologies dependent on cheap oil. The disciplinary inputs to modern urban design are still generally limited to the traditional practices that have shaped our fossil fuel based urban forms. Urban design collaboration at the city level is still undertaken on a very narrow platform with goals fixed by short-term political cycles rather than true community and environmental benefit.
The biocity studio urges cities to begin a comprehensive interrogation and assessment of their 12 constituent systems against predetermined climate change, population growth and oil cessation crisis scenarios.
According to the IPCC the major challenges to be faced by Australian cities in the near future include sea-level rise, falls in agricultural production, loss of biodiversity assets, decreasing water availability and increasing drought, increased flood and storm damage, heatwave and bushfire risk, changing distribution of disease vectors and exposure to infectious diseases.[figure 17] Planning decisions should aim to boost resilience in each of the major risk areas.27
Biocity further postulates that post-oil urban settlements will need to transmute their urban fabric into organically arranged, interconnected human ecologies, whereby no process or material would be considered an externality. In the biocity, every input and output has to be factored as a biophysical or metabolic stream that contributes to the collective well being of the inhabitants and the place. Through diversity comes resilience.
Most of the world’s agricultural systems are based on ecologically frail monocultures that require huge carbon, water and nitrogen inputs. Modern agribusiness needs inexpensive gas and oil inputs for fertilisers, pesticides, machinery, planting, cultivating, harvesting, processing, packaging, transportation and marketing.
The World Bank’s 2008 Agriculture for development report28 states we are living in the most acute food shortage of the past 40 years and already 800 million people are food insecure. It identifies that cereal production must increase by 50 per cent and meat production by 85 per cent of 2000 levels to meet the expected 2030 global demand.
Considering that the IPCC warns that agricultural production will decline under climate change and that production of one kilogram of beef requires about 15,500 litres of water29 this projection is unlikely to ever be met. The trend towards biofuel production is further eroding our ability to feed the global population. It is self-evident that the growing ecofootprint of the urbanised world is rapidly moving beyond the threshold capacity of the Earth to supply.
The report further identifies that there are 900 million rural people in the developing world who live on less than $1 a day, most of whom are engaged in agriculture. The disparities in the global fossil fuel agribusiness system are obvious and the short comings of our linear economic model clear. Biocity proposes that we must move away from an isolationist food production system to an integrated model where agricultural inputs and outputs are considered as vital elements of the total ecosystem.
As a poignant example of political indifference to climate change and food security in Australia, the current metropolitan strategy for Sydney proposes 195,000 homes be located in two new areas of land release to the west of the city.
Landscape architect Jeremy Gill has found Western Sydney accounts for only 2.5 per cent of the state’s land and yet supplies 20 per cent of its total vegetable production.30 This planned urban sprawl will consume a major portion of productive, intensively farmed land.[figure 18] This politically supported, fossil fuel based planning decision to favour housing sprawl over feeding the city, is representational of our failure to consider the effect major urban decisions have on the total urban biotope.
In 2008 Hans-Josef Fell, Member of the German Bundestag, visited Australia. He addressed a small but interested following at the UNSW law building in Sydney. His lecture outlined that in 2000, “the Members of the German Parliament set a target in the Renewable Energy Sources Act for 12.5 per cent of electricity to come from renewable sources by 2010. We were told that this target was unrealistic and unachievable. And yet at the end of 2007 a 14 per cent share has already been achieved.”31
Germany is leading the world in solar and wind energy renewable production, primarily through the introduction of a national feed-in tariff.33[figure 19 and 20] This tariff is an example of a bioeconomic incentive that values clean energy natural capital higher than dirty energy. As the German experience demonstrates, it is possible to achieve 100 per cent of global baseload power from renewables if intelligent national policies are in place.
The potential for entire bioregions to meet their own energy demand is demonstrably within the realms of current technology. Australia continues to perform poorly in renewables production.[figure 21 and 22] The remaining oil reserves we have should be diverted to macro scale production of renewable energy. Once these bioenergy systems are in place our urban ecosystems can mimic the photosynthetic processes of nature.
Biocities will be characterised by decentralised and diversified local infrastructure networks augmented by remnants of the industrial infrastructure grid. In the biocity, dwelling density will need to be focused around walkable city centres well serviced by public transport. Building heights would be mid- to low-rise in traditional village forms to minimise energy use.
Tall buildings may also become obsolete being too energy intensive to operate unless they can be stripped of their curtain walls and retrofitted into stacked productive agricultural cells Ken Yeang style.
New buildings will be passively heated and cooled as they were before modern architecture hermetically sealed off the indoors from the outdoors. The biocity will focus effort on repairing its centre instead of wasting energy on sprawling peri urban structures.[figure 23 and 24]
Our cities will enter a “‘post mobility”‘ phase where the car itself, made affordable to the masses by Henry Ford through mass production, will return to being an elite form of transport. Without the cheap oil to manufacture plastics, metals and components needed for new cars, existing vehicles will have to be retrofitted for electric use until wear and tear brings them to their end, Mad Max style.
The maintenance of road networks without oil sludge to manufacture asphalt will require abandonment of much of the existing suburban road infrastructure if a replacement cannot be found. As vehicular travel becomes increasingly untenable for the average citizen many sprawling suburbs may have to be abandoned as unserviceable.
This has already occurred in some parts of the US and Europe where industrial cities have been shrinking as manufacturing moves offshore to third world countries. [figure 25] Suburbia may serve a new purpose as a source of building materials to consolidate walkable city centres serviced by public transport. Its demolition could also make available productive areas for agriculture adjacent to cities.
Urban golf courses could become useful for food production, having water supply and irrigation practices already in place. The magnitude of this proposition is apparent when one considers that half of the US, about 150 million people, live in suburbia. Cuban cities are a good working example of peak oil adaptation where an oil embargo has pushed the entire nation into organic permaculture based food production. Urban food production, or terraponics, has become central to everyday life and agricultural knowledge is highly sought after.[figure 26]
An important part of the process in achieving urban sustainability is the measurement of relative urban health. New metric tools for assessing the isolated micro environmental and cultural impact of individual buildings have appeared but these are not coupled to any overarching regional metric.
Biocity proposes the introduction of a new metric tool that captures critical quantitative and qualitative supra-systems data called The Biocity Health Index. This index is currently under construction. Current indices on city competiveness are based on traditional fossil fuel based indicators and are usually tied to arbitrary GDP or lifestyle parameters. The Biocity Health Index rates a broad range of subsystems that fall under the 12 main systems. By attracting open-source information through a transparent Wiki-like interface, global internet collaboration can be harnessed. The plan is to make this comparative data publicly available so that citizens are empowered to lobby for political change in their regions.
Our generations will be judged for their actions on the converging emergencies of the 21st century. Cities will be the places where the most dramatic impacts of climate change and peak oil will be felt. Biocity proposes that we must heed the calls of the IPCC and respond by taking urgent action to fundamentally rethink fossil fuel based design and planning dogma. By acknowledging that cities are fragile ecosystems reliant on the ecological services of their neighbouring environments we must transition to whole of systems thinking. The Biocity model adopts a biomimicry agenda that considers the balance of a total system and the equity between its parts as paramount. Biocity can become an antidote to fossil fuel planning and a productive theoretical tool for changing the course of history.
The term biocity alludes to a bridging of the gap in the notion that city and country are disconnected entities.[figure 27] If we do not recognise our place inside nature and change our attitude from superior being to equal partner it is quite likely that the human race will be consumed by evolution itself.Adrian McGregor is a Landscape Architecture and Urban Design professional and managing director of mcgregor+partners, a Sydney based environmental design studio. After graduating with a Bachelor of Landscape Architecture in 1988, he worked in Sydney before moving to North America and Britain to work on a range of environmental projects. He founded mcgregor+partners in 1998 and the Biocity Studio in 2006 to combine practice with research in pursuit of a sustainable design ethic. email@example.com
1. Kunstler, J., 2005: The long emergency, Atlantic Monthly Press p.12
2. Jackson, Dr. Richard Joseph, 2004: Urban Sprawl and Public Health, Island Press
3. The Electric Wallpaper Co., 2004: – The End of Surburbia: Oil Depletion and the Collapse of The American Dream. Movie hosted by Barrie Zwicker. Directed by Gregory Greene. Produced by Barry Silverthorn.
9. https://www.ipcc.ch/pdf/presentations/briefing-bonn-2008-06/greenhouse-gas concentrations.pdf
10. Australian Broadcasting Corporation, 2007: Crude – The incredible journey of oil. Movie written and produced by Dr. Richard Smith.
11. Suzuki, Dr. David, 2006: Designing Sustainable Futures : Setting the real bottom line – Conference speech – 2006 Global Eco design dialogues. Cairns.
12. Hawkens, P, Lovins A, Lovins, LH:1999: Natural Capitalism-Creating the next industrial revolution. Little, Brown.
14. Hamilton, James D., 1983: Oil and the Macroeconomy since World War II, The University of Chicago Press.
15. Newman, Peter, Dr. and Jennings, Isabella. 2008: Cities as sustainable ecosystems. Island Press. p2 – p238
18. United Nations, 2007: World Urbanization Prospects – The 2007 Revision. New York.
22. de duve, C. 1195. Vital dust: Life as a cosmic imperative. New York: Basic books
23. Vasishth, Ashwani, Sloane, David, 2002: Returning to ecology: An ecosystem approach To understanding the City By, www.csun.edu/~vasishth/Vasishth+Returning_To_Ecology.pdf
25. Berry, W. 1991: Out of your car, off your horse: Twenty-seven propositions about global thinking and the sustainability of cities. Atlantic Monthly 267 : 61-63
26. McDonough, William, Braungart Michael, 2002: Cradle to Cradle – Remaking the way we make things, North Point Press.
27. IPCC, 2007: Climate Change 2007:Synthesis Report – An Assessment of the Intergovernmental Panel on Climate Change IPCC Plenary XXVII (Valencia, Spain, 12-17 November 2007). p51.
28. The World Bank. 2008: World Development Report 2008 – Agriculture for Development. Washington DC. ISBN-13: 978-0-8213-6807-7
30. Gill, Jeremy, 2008: The effect of urban sprawl on Sydney’s peri-urban agricultural region. UNSW
31. Fell, Hans-Josef, 2008: The solution for climate protection and energy security – The Third Industrial Revolution: The Economy for Climate Policy. Lecture UNSW, Law Building 14.5.2008.
32. Ewing B., S. Goldfinger, M. Wackernagel, M. Stechbart, S. M. Rizk, A. Reed and J. Kitzes, 2008: The Ecological Footprint Atlas 2008. Oakland: Global Footprint Network.
33. U.S. Department Energy, 2008: Renewable Energy Data Book. Energy Efficiency &Renewable Energy.