Ecological footprint

Ecological footprint

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The ecological footprint is a measure of human demand on the Earth's ecosystems. It is a standardized measure of demand for natural capital
Natural capital
Natural capital is the extension of the economic notion of capital to goods and services relating to the natural environment. Natural capital is thus the stock of natural ecosystems that yields a flow of valuable ecosystem goods or services into the future...

 that may be contrasted with the planet's ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 capacity to regenerate. It represents the amount of biologically productive land and sea area necessary to supply the resources a human population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

 consumes, and to mitigate
Environmental mitigation
Environmental mitigation, compensatory mitigation, or mitigation banking, are terms used primarily by the United States government and the related environmental industry to describe projects or programs intended to offset known impacts to an existing historic or natural resource such as a stream,...

 associated waste. Using this assessment, it is possible to estimate how much of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 (or how many planet Earths) it would take to support humanity if everybody followed a given lifestyle. For 2006, humanity's total ecological footprint was estimated at 1.4 planet Earths – in other words, humanity uses ecological services 1.4 times as fast as Earth can renew them. Every year, this number is recalculated — with a three year lag due to the time it takes for the UN to collect and publish all the underlying statistics.

While the term ecological footprint is widely used, methods of calculation vary. However, standards are now emerging to make results more comparable and consistent.

Analysis



Overview


The first academic publication about the ecological footprint was by William Rees in 1992. The ecological footprint concept and calculation method was developed as the PhD dissertation of Mathis Wackernagel
Mathis Wackernagel
Mathis Wackernagel is a Swiss-born sustainability advocate. He is currently President of Global Footprint Network, an international sustainability think tank with a presence in Oakland, California; Brussels, Belgium, and Zurich, Switzerland...

, under Rees' supervision at the University of British Columbia
University of British Columbia
The University of British Columbia is a public research university. UBC’s two main campuses are situated in Vancouver and in Kelowna in the Okanagan Valley...

 in Vancouver, Canada, from 1990–1994. Originally, Wackernagel and Rees called the concept "appropriated carrying capacity". To make the idea more accessible, Rees came up with the term "ecological footprint," inspired by a computer technician who praised his new computer's "small footprint on the desk." In early 1996, Wackernagel and Rees published the book Our Ecological Footprint: Reducing Human Impact on the Earth.

Ecological footprint analysis compares human demand on nature with the biosphere's ability to regenerate resources and provide services. It does this by assessing the biologically productive land and marine area required to produce the resources a population consumes and absorb the corresponding waste, using prevailing technology. Footprint values at the end of a survey are categorized for Carbon, Food, Housing, and Goods and Services as well as the total footprint number of Earths needed to sustain the world's population at that level of consumption. This approach can also be applied to an activity such as the manufacturing of a product or driving of a car. This resource accounting is similar to life cycle analysis wherein the consumption of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

, biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 (food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

, fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....

), building material
Building material
Building material is any material which is used for a construction purpose. Many naturally occurring substances, such as clay, sand, wood and rocks, even twigs and leaves have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more...

, water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 and other resources
Natural resource
Natural resources occur naturally within environments that exist relatively undisturbed by mankind, in a natural form. A natural resource is often characterized by amounts of biodiversity and geodiversity existent in various ecosystems....

 are converted into a normalized measure of land area called 'global hectare
Global hectare
The global hectare is a measurement of biocapacity of the entire earth - one global hectare is a measurement of the average biocapacity of all hectare measurements of any biologically productive areas on the planet. If you take the sum of the world's biocapacity, then divide it by the number...

s' (gha).

Per capita ecological footprint (EF) is a means of comparing consumption and lifestyles, and checking this against nature's ability to provide for this consumption. The tool can inform policy by examining to what extent a nation uses more (or less) than is available within its territory, or to what extent the nation's lifestyle would be replicable worldwide. The footprint can also be a useful tool to educate people about carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...

 and over-consumption
Over-consumption
Over-consumption is a situation where resource-use has outpaced the sustainable capacity of the ecosystem. A prolonged pattern of overconsumption leads to inevitable environmental degradation and the eventual loss of resource bases...

, with the aim of altering personal behavior. Ecological footprints may be used to argue that many current lifestyles are not sustainable
Sustainable development
Sustainable development is a pattern of resource use, that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for generations to come...

. Such a global comparison also clearly shows the inequalities of resource use on this planet at the beginning of the twenty-first century.

In 2006, the average biologically productive area per person worldwide was approximately 1.8 global hectare
Global hectare
The global hectare is a measurement of biocapacity of the entire earth - one global hectare is a measurement of the average biocapacity of all hectare measurements of any biologically productive areas on the planet. If you take the sum of the world's biocapacity, then divide it by the number...

s (gha) per capita. The U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 footprint per capita was 9.0 gha, and that of Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 was 5.6 gha per person, while China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

's was 1.8 gha per person. The WWF
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...

 claims that the human footprint has exceeded the biocapacity (the available supply of natural resources) of the planet by 20%. Wackernagel and Rees originally estimated that the available biological capacity for the 6 billion people on Earth at that time was about 1.3 hectares per person, which is smaller than the 1.8 global hectares published for 2006, because the initial studies neither used global hectares nor included bioproductive marine areas.

A number of NGO websites allow estimation of one's ecological footprint (see Footprint Calculator, below).

Ecological footprint analysis is now widely used around the globe as an indicator of environmental sustainability
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...

. It can be used to measure and manage the use of resources throughout the economy. It can be used to explore the sustainability of individual lifestyles, goods and services, organizations, industry sectors, neighborhoods, cities, regions and nations. Since 2006, a first set of ecological footprint standards exist that detail both communication and calculation procedures. They are available at www.footprintstandards.org and were developed in a public process facilitated by Global Footprint Network and its partner organizations.

Methodology


The ecological footprint accounting method at the national level is described in the Ecological Footprint Atlas 2010 or in more detail in the Calculation Methodology for the National Footprint Accounts . The National Accounts Review Committee has also published a research agenda on how the method will be improved.

There have been differences in the methodology used by various ecological footprint studies. Examples include how sea area should be counted, how to account for fossil fuels, how to account for nuclear power (many studies simply consider it to have the same ecological footprint as fossil fuels), which data sources used, when average global numbers or local numbers should be used when looking at a specific area, how space for biodiversity should be included, and how imports/exports should be accounted for.http://www.bestfootforward.com/downloads/Use%20of%20EF%20for%20SGA%20-%20Main%20Report.PDF.http://www2.pccu.edu.tw/CUEQ/fulltext/96林士堅論文.doc However, with the new footprint standards, the methods are converging.

In 2003, Jason Venetoulis, PhD, Carl Mas, Christopher Gudoet, Dahlia Chazan, and John Talberth -a team of researchers at Redefining- developed Footprint 2.0. Footprint 2.0 offers a series of theoretical and methodological improvements to the standard footprint approach. The primary advancements were to include the entire surface of the Earth in biocapacity estimates, allocate space for other (non-human) species, change the basis of equivalence factors from agricultural land to net primary productivity (NPP), and change the carbon component of the footprint, based on global carbon models. The advancements were peer reviewed and published in several books, and have been well received by teachers, researchers, and advocacy organizations concerned about the ecological implications of humanity's footprint.

Studies in the United Kingdom


The UK's average ecological footprint is 5.45 global hectare
Global hectare
The global hectare is a measurement of biocapacity of the entire earth - one global hectare is a measurement of the average biocapacity of all hectare measurements of any biologically productive areas on the planet. If you take the sum of the world's biocapacity, then divide it by the number...

s per capita (gha) with variations between regions ranging from 4.80 gha (Wales) to 5.56 gha (East England). Two recent studies have examined relatively low-impact small communities. BedZED
BedZED
Beddington Zero Energy Development is an environmentally friendly housing development in Hackbridge, London, England. It is in the London Borough of Sutton. It was designed by the architect Bill Dunster to support a more sustainable lifestyle...

, a 96-home mixed-income housing development in South London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, was designed by Bill Dunster Architects and sustainability consultants BioRegional for the Peabody Trust
Peabody Trust
Peabody Trust , founded in 1862, is one of London's oldest and largest housing associations with over 19,000 properties. It also a charity and urban regeneration agency...

. Despite being populated by relatively "mainstream" home-buyers, BedZED was found to have a footprint of 3.20 gha due to on-site renewable energy production, energy-efficient architecture, and an extensive green lifestyles program that included on-site London's first carsharing
Carsharing
Car sharing or Carsharing is a model of car rental where people rent cars for short periods of time, often by the hour. They are attractive to customers who make only occasional use of a vehicle, as well as others who would like occasional access to a vehicle of a different type than they use...

 club. The report did not measure the added footprint of the 15,000 visitors who have toured BedZED since its completion in 2002. Findhorn Ecovillage
Findhorn Ecovillage
Findhorn Ecovillage is an experimental architectural community project based at The Park, in Moray, Scotland, near the village of Findhorn. The project's main aim is to demonstrate a sustainable development in environmental, social, and economic terms...

, a rural intentional community
Intentional community
An intentional community is a planned residential community designed to have a much higher degree of teamwork than other communities. The members of an intentional community typically hold a common social, political, religious, or spiritual vision and often follow an alternative lifestyle. They...

 in Moray
Moray
Moray is one of the 32 council areas of Scotland. It lies in the north-east of the country, with coastline on the Moray Firth, and borders the council areas of Aberdeenshire and Highland.- History :...

, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, had a total footprint of 2.56 gha, including both the many guests and visitors who travel to the community to undertake residential courses there and the nearby campus of Cluny Hill
Cluny Hill
Cluny Hill is a hill on south side of Forres, Scotland.At the top of Cluny Hill is Nelson's Tower, built in 1806 to commemorate Admiral Lord Nelson and his victory at Trafalgar. The Tower is open to the public....

 College. However, the residents alone have a footprint of 2.71 gha, a little over half the UK national average and one of the lowest ecological footprints of any community measured so far in the industrialized world Keveral Farm, an organic farming community in Cornwall, was found to have a footprint of 2.4 gha, though with substantial differences in footprints among community members.

Discussion


Early criticism was published by van den Bergh and Verbruggen in 1999; another criticism was published in 2008. A more complete review commissioned by the Directorate-General for the Environment (European Commission)
Directorate-General for the Environment (European Commission)
The Directorate-General for the Environment is a Directorate-General of the European Commission, responsible for the European Union policy area of the environment....

 and published in June 2008 provides the most updated independent assessment of the method. A number of countries have engaged in research collaborations to test the validity of the method. This includes Switzerland, Germany, United Arab Emirates, and Belgium.

Grazi et al. (2007) have performed a systematic comparison of the ecological footprint method with spatial welfare analysis that includes environmental externalities
Externality
In economics, an externality is a cost or benefit, not transmitted through prices, incurred by a party who did not agree to the action causing the cost or benefit...

, agglomeration effects and trade advantages. They find that the two methods can lead to very distinct, and even opposite, rankings of different spatial patterns of economic activity. However, this should not be surprising, since the two methods address different research questions.

Calculating the ecological footprint for densely populated areas, such as a city or small country with a comparatively large population — e.g. New York and Singapore respectively — may lead to the perception of these populations as "parasitic". This is because these communities have little intrinsic biocapacity, and instead must rely upon large hinterland
Hinterland
The hinterland is the land or district behind a coast or the shoreline of a river. Specifically, by the doctrine of the hinterland, the word is applied to the inland region lying behind a port, claimed by the state that owns the coast. The area from which products are delivered to a port for...

s. Critics argue that this is a dubious characterization since mechanized rural farmers in developed nations may easily consume more resources than urban inhabitants, due to transportation requirements and the unavailability of economies of scale
Economies of scale
Economies of scale, in microeconomics, refers to the cost advantages that an enterprise obtains due to expansion. There are factors that cause a producer’s average cost per unit to fall as the scale of output is increased. "Economies of scale" is a long run concept and refers to reductions in unit...

. Furthermore, such moral conclusions seem to be an argument for autarky
Autarky
Autarky is the quality of being self-sufficient. Usually the term is applied to political states or their economic policies. Autarky exists whenever an entity can survive or continue its activities without external assistance. Autarky is not necessarily economic. For example, a military autarky...

. Some even take this train of thought a step further, claiming that the Footprint denies the benefits of trade. Therefore, the critics argue that the Footprint can only be applied globally.
The method seems to reward the replacement of original ecosystems with high-productivity agricultural monoculture
Monoculture
Monoculture is the agricultural practice of producing or growing one single crop over a wide area. It is also known as a way of farming practice of growing large stands of a single species. It is widely used in modern industrial agriculture and its implementation has allowed for large harvests from...

s by assigning a higher biocapacity to such regions. For example, replacing ancient woodlands or tropical forests with monoculture forests or plantations may improve the ecological footprint. Similarly, if organic farming
Organic farming
Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...

 yields were lower than those of conventional methods, this could result in the former being "penalized" with a larger ecological footprint. Of course, this insight, while valid, stems from the idea of using the footprint as one's only metric. If the use of ecological footprints are complemented with other indicators, such as one for biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

, the problem could maybe be solved. Indeed, WWF
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...

's Living Planet Report
Living Planet Index
The Living Planet Index is an indicator of the state of global biological diversity, based on trends in vertebrate populations of species from around the world....

 complements the biennial Footprint calculations with the Living Planet Index of biodiversity. Manfred Lenzen and Shauna Murray have created a modified Ecological Footprint that takes biodiversity into account for use in Australia.

Although the ecological footprint model prior to 2008 treated nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

 in the same manner as coal power, the actual real world effects of the two are radically different. A life cycle analysis centered on the Swedish Forsmark Nuclear Power Plant
Forsmark Nuclear Power Plant
Forsmark Nuclear Power Plant is a nuclear power plant in Forsmark, Sweden, and also the site of the Swedish Final repository for radioactive operational waste...

 estimated carbon dioxide emissions at 3.10 g/kWh and 5.05 g/kWh in 2002 for the Torness Nuclear Power Station
Torness nuclear power station
Torness nuclear power station was the last of the United Kingdom's second generation nuclear power plants to be commissioned. Construction of this facility began in 1980 for the then South of Scotland Electricity Board and it was commissioned in 1988...

. This compares to 11 g/kWh for hydroelectric power, 950 g/kWh for installed coal, 900 g/kWh for oil and 600 g/kWh for natural gas generation in the United States in 1999. Figures released by Mark Hertsgaard, however, show that because of the delays in building nuclear plants and the costs involved, investments in energy efficiency and renewable energies have seven times the return on investment of investments in nuclear energy.

The Swedish utility Vattenfall
Vattenfall
Vattenfall is a Swedish power company. The name Vattenfall is Swedish for waterfall, and is an abbreviation of its original name, Royal Waterfall Board...

 did a study of full life cycle emissions of Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind which the utility uses to produce electricity. The net result of the study was that nuclear power produced 3.3 grams of carbon dioxide per KW-Hr of produced power. This compares to 400 for natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

 and 700 for coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 (according to this study). The study also concluded that nuclear power produced the smallest amount of CO2 of any of their electricity sources.

Claims exist that the problems of nuclear waste do not come anywhere close to approaching the problems of fossil fuel waste. A 2004 article from the BBC states: "The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 (WHO) says 3 million people are killed worldwide by outdoor air pollution annually from vehicles and industrial emissions, and 1.6 million indoors through using solid fuel." In the U.S. alone, fossil fuel waste kills 20,000 people each year. A coal power plant releases 100 times as much radiation as a nuclear power plant of the same wattage. It is estimated that during 1982, US coal burning released 155 times as much radioactivity into the atmosphere as the Three Mile Island incident. In addition, fossil fuel waste causes global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

, which leads to increased deaths from hurricanes, flooding, and other weather events. The World Nuclear Association
World Nuclear Association
The World Nuclear Association , formerly the Uranium Institute, is an international organization that promotes nuclear power and supports the many companies that comprise the global nuclear industry...

 provides a comparison of deaths due to accidents among different forms of energy production. In their comparison, deaths per TW-yr of electricity produced (in UK and USA) from 1970 to 1992 are quoted as 885 for hydropower, 342 for coal, 85 for natural gas, and 8 for nuclear.

By country


See also



  • Carbon footprint
    Carbon footprint
    A carbon footprint has historically been defined as "the total set of greenhouse gas emissions caused by an organization, event, product or person.". However, calculating a carbon footprint which conforms to this definition is often impracticable due to the large amount of data required, which is...

  • Water footprint
    Water footprint
    The water footprint of an individual, community or business is defined as the total volume of freshwater used to produce the goods and services consumed by the individual or community or produced by the business. Water use is measured in water volume consumed and/or polluted per unit of time. A...

  • Dependency theory
    Dependency theory
    Dependency theory or dependencia theory is a body of social science theories predicated on the notion that resources flow from a "periphery" of poor and underdeveloped states to a "core" of wealthy states, enriching the latter at the expense of the former...

  • Ecological economics
    Ecological economics
    Image:Sustainable development.svg|right|The three pillars of sustainability. Clickable.|275px|thumbpoly 138 194 148 219 164 240 182 257 219 277 263 291 261 311 264 331 272 351 283 366 300 383 316 394 287 408 261 417 224 424 182 426 154 423 119 415 87 403 58 385 40 368 24 347 17 328 13 309 16 286 26...

  • Ecosystem valuation
    Ecosystem valuation
    Ecosystem valuation is a widely used tool in determining the impact of human activities on an environmental system, by assigning an economic value to an ecosystem or its ecosystem services.-Value of ecosystem services:...

  • Environmental impact assessment
    Environmental impact assessment
    An environmental impact assessment is an assessment of the possible positive or negative impact that a proposed project may have on the environment, together consisting of the natural, social and economic aspects....

  • Greenhouse debt
    Greenhouse debt
    Greenhouse debt or carbon debt is the measure to which an individual person, incorporated association, business enterprise, government instrumentality or geographic community exceeds its permitted greenhouse footprint and contributes greenhouse gases that contribute to global warming and climate...

  • Life cycle assessment
    Life cycle assessment
    A life-cycle assessment is a technique to assess environmental impacts associated with all the stages of a product's life from-cradle-to-grave A life-cycle assessment (LCA, also known as life-cycle analysis, ecobalance, and cradle-to-grave analysis) is a technique to assess environmental impacts...

  • Limits to Growth
    Limits to Growth
    The Limits to Growth is a 1972 book modeling the consequences of a rapidly growing world population and finite resource supplies, commissioned by the Club of Rome. Its authors were Donella H. Meadows, Dennis L. Meadows, Jørgen Randers, and William W. Behrens III. The book used the World3 model to...

  • Netherlands fallacy
    Netherlands fallacy
    The Netherlands fallacy refers to an error in assuming that the environmental impacts of the Netherlands and other rich nations are contained within their national borders....

  • Physical balance of trade
  • Simon–Ehrlich wager
  • The Population Bomb
    The Population Bomb
    The Population Bomb was a best-selling book written by Paul R. Ehrlich and his wife, Anne Ehrlich , in 1968. It warned of the mass starvation of humans in the 1970s and 1980s due to overpopulation, as well as other major societal upheavals, and advocated immediate action to limit population growth...

  • List of environmental issues


Further reading

  • Rees, W. E. and M. Wackernagel (1994) Ecological footprints and appropriated carrying capacity: Measuring the natural capital requirements of the human economy, in Jansson, A. et al.. Investing in Natural Capital: The Ecological Economics Approach to Sustainability. Washington D.C.:Island Press. ISBN 1-55963-316-6
  • Wackernagel, M. and W. Rees. 1996. Our Ecological Footprint: Reducing Human Impact on the Earth. Gabriola Island, BC: New Society Publishers. ISBN 0-86571-312-X.
  • WWF, Global Footprint Network, Zoological Society of London (2006) Living Planet Report 2006. WWF Gland, Switzerland. (downloadable in 11 languages via http://www.footprintnetwork.org/newsletters/gfn_blast_0610.html)
  • Lenzen, M. and Murray, S. A. 2003. 'The Ecological Footprint – Issues and Trends.' ISA Research Paper 01-03
  • Chambers, N., Simmons, C. and Wackernagel, M. (2000), Sharing Nature's Interest: Ecological Footprints as an Indicator of Sustainability. Earthscan, London ISBN 1-85383-739-3 (see also http://www.ecologicalfootprint.com)

External links