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9.3: Derivative Life Cycle Concepts

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  • Sustainability Metrics and Rating Systems


    The ideal method to measure sustainability would reflect the three-legged stool paradigm – environmental protection, social equity, and economic benefit. The metrics must make the connection between what the indicators measure and actual sustainability. A useful indicator will reflect changes over time that show whether a system is becoming more or less sustainable, and generally substitutes for something else or represents several measures (Sahely, 2005). The challenge of studying sustainability as an objective science is that the work is value-loaded and socially charged. If we are aware of the purpose of the analysis we can use a multidisciplinary approach to the problem definition and the research methodology (Lele and Norgaard, 1996).

    Information Pyramid
    Figure \(\PageIndex{1}\) Information Pyramid The Information Pyramid shows ways of handling data when studying sustainability. Source: C. Klein-Banai.

    In general, three approaches to sustainability measurement and reporting are commonly utilized: accounts that use quantitative data and convert them to a common unit such as money, area or energy; narrative assessments that include text, maps, graphics and tabular data; and indicator-based systems that may include the information that a narrative assessment has but they are organized around indicators or measurable parts of a system. Indicator-based systems are generally found to perform better and are easily measurable and comparable since they are more objective than narrative systems, or use only individual data points (Dalal-Clayton, 2002). Decision-makers and stakeholders need to participate in the development of indicators to be sure that their values and concerns are addressed. However, the system does need to be technically and scientifically based.

    In the next few modules we will briefly discuss existing sustainability metrics that are generally based within certain disciplines such as ecology, economics, and physics, and how they may reflect other disciplines (see Table \(\PageIndex{1}\)). Most of these metrics are described in greater details in the following modules: The IPAT Equation, Biodiversity, Species Loss, and Ecosystem Function, Tragedy of the Commons, Environmental Valuation, Evaluating Projects and Policies, and Life Cycle Assessment.

    Method Brief Description



    Contingent valuation method (CVM) Captures the preferences of the public regarding a good or service by measuring its willingness to pay Good or service
    Ecosystem services valuation Valuation of services provided by nature such as cleaning of water by microorganisms Good or service
    Cost Benefit Analysi(CBA) Valuation of cost and benefits for each year of project/policy; calculation of a net present value (NPV) by aggregating and comparing costs and benefits over the whole life of project policy. Project or policy
    Index of Sustainable Economic Welfare (ISEW) Weights personal expenditures with an index of income inequality Regional welfare
    Net national product (NNP) Total income of the people in an economy less capital consumption or depreciation Regional welfare
    Green NNP Modification of above to account for loss of natural resource capital Regional welfare
    Resilience Intensity of disturbance required to move system to a new regime Ecosystem
    Carrying capacity: Maximum sustainable yield (MSY) & IPAT The maximum amount of resource extraction while not depleting the resource from one harvest to the next Ecosystem
    Ecological Ecological footprint (EF) Total area of productive land and water ecosystems needed to produce resources and assimilate waste of a given population Individual, institutional, regional


    Energy The amount of solar energy that has been used directly or indirectly to make a good or service Good or service
    Exergy The maximum work that can be extracted from a system when it moves towards thermodynamic equilibrium with a reference state Policy, evaluation of energy systems

    Table \(\PageIndex{1}\) Common Sustainability MetricsTable lists common sustainability metrics. Source: C. Klein-Banai

    Ecological Measures

    Ecological measures of sustainability are used for natural systems. These measures include resilience and several constructs that are derivatives from carrying capacity. Resilience is the time needed for a system that provides desirable ecosystem goods and services to go back to a defined dynamic regime after disturbance. Resilience stresses the changing nature of ecosystems, rather than seeing them as static and providing a continuous and constant amount of natural resources. Carrying capacity estimates society’s total use of the resource stocks and flows provided by an ecosystem relative to the remaining resources needed by the ecosystem for stability and regeneration. Maximum sustainable yield (MSY) is an outgrowth of carrying capacity and the goal is to reach the maximum amount of resource extraction while not depleting the resource from one harvest to the next. Sustainability, in this context, can be understood as the point when the rate of resource extraction or harvest (MSY) equals the amount produced by the ecosystem. Previously discussed methods are types of measures of sustainability such as IPAT (see Module The IPAT Equation) which accounts for the effect of society on the amount of resources used when looking at carrying capacity. This type of measure looks at whether the impact of a human society is increasing or decreasing over time and can be used to compare impacts between societies of difference sizes or affluence levels.

    Footprinting (see Module Footprinting: Carbon, Ecological and Water) is often used as a measure of sustainability that can be understood intuitively and is, therefore, useful when talking to the general public. The ecological footprint, which also represents the carrying capacity of the earth, is defined as “the total area of productive land and water ecosystems required to produce the resources that the population consumes and assimilate the wastes that the population produces, wherever on Earth that land and water may be located” (Rees and Wackernagel, 1996). This results in an evaluation of the demand and supply of natural capital of a given population (individual to planet) or a product/service.

    Life-cycle assessment (LCA), a structured methodology that can be utilized to evaluate the environmental impacts of products, processes, projects, or services throughout their life cycles from cradle to grave (see Module Life Cycle Assessment) may be considered an ecological metric. A greenhouse gas emissions inventory is an example of this methodology (see Case Study: Greenhouse Gases and Climate Change).

    Economic Measures

    Economic measures place a monetary value on sustainability. Economists use the following measures of sustainability: ecosystem valuation, contingent valuation, and net national product, which are discussed in Chapter . Standard economic methods can be used to evaluate environmental projects.

    Indices that are used on a national and international level by organizations like the United Nations may be used to examine the economic and social welfare of a region. The Index of Sustainable Economic Welfare (ISEW) and other related frameworks that account for sustainable development have been conceived to provide an alternative to the Gross Domestic Product, which does not capture human welfare in its calculations. This system weights personal expenditures within a population with an index of income inequality and a set of factors are then added or subtracted to this monetary value. Monetary analysis of sustainability does not value the variety of sustainability issues especially those that cannot be measured as a product or service in today’s markets (Gasparatos, et al., 2008).

    Physical Measures

    Physical measures of sustainability use thermodynamic concepts in their calculations. Two physical approaches to measuring sustainability are exergy and emergy. These concepts are derived from the second law of thermodynamics which states that a closed system with constant mass and no energy inputs tends toward higher entropy or disorder. For instance, a piece of wood that is the product of many years of complex tree growth releases energy (light and heat in the flame) when burned, and becomes carbon ash, smoke, gases, and water vapor. This means that as properties within a system such as mass, energy, and chemical concentrations degrade (decompose) over time or burn, they also make available useful energy (exergy) for work. Ecosystems and human economies function under this second law, but they can use external energy (the sun) to maintain or increase energy supplies.

    Emergy is the amount of energy of one kind (solar) that has been used directly or indirectly (through a transformation process) to make a service or a product of one type and it is expressed in units of (solar energy) emjoule. It can be thought of as a measure of all the entropy that has been produced over the whole process of creating a given product or service (Brown and Ulgiati, 2002). An example is the process of fossil fuel creation: solar energy was used by plants to grow and is stored in the complex molecular structures that held the plants together, when those plants died they decomposed and were buried over time under the changing earth, and the energy was concentrated into fossil fuels. Emergy, thus, allows us to account for all the environmental support needed by human and eco-systems or inputs.

    Measures of energy inputs are transformed to emergy by use of a factor that represents the amount of environmental work needed to produce a product or provide a service. The emergy flows within a system include renewable resources (sunlight, rain, wind, agricultural production, timber harvest, etc.), non-renewable production (fossil fuels, metals, minerals, soils), and imports/exports. A sustainable system would have a net positive (or zero) emergy flow across its boundary (Mayer, et al., 2004). Emergy evaluations have been used, for instance, to quantitatively demonstrate that renewable energy plants had higher sustainability compared to thermal plants (Brown and Ugliati, 2002).

    Exergy can be defined as the maximum work that can be extracted from a system as it moves to thermodynamic equilibrium with a reference state, as in the example of burned wood above. It has been used to study efficiency of chemical and thermal processes. This represents an entropy-free form of energy that is a measure of its usefulness, quality or potential to make change. Exergy accounting provides insights into the metabolism of a system and its effect on the environment using a common denominator. It can address energy utilization, be used for design and analysis of energy systems and to quantify waste and energy losses reflecting resource use. Exergy can account for an economic component, labor input, and impact of emissions on human health (Gasparatos, et al., 2008; Odum, 1996).

    Comparison of Measures

    So far we highlighted three categories for measures of sustainability – ecological, economic, and physical – and provided a few examples. Sustainability measures is an evolving field of study and the metrics are innumerable. Ecological measures include indicators that try to measure the sustainability of the ecosystem as a whole. Economic metrics use monetary measures and try to put a price on the environment and its services. They are valued based on currency, which is an anthropocentric value, meaning it is significant only to humans. They account only for human welfare to the extent that it depends on nature to survive. They do not account for the effect on an ecosystem as a whole, including plants and animals. Physical metrics are closely tied to thermodynamics and energy, and are generally expressed in units of energy.

    Sustainability indicators are needed to improve our understanding of the nature of human demands on ecosystems and the extent to which these can be modified. Society uses resources for physical and social infrastructure and continually increases its needs due to population growth which is made possible by changing the way we grow and produce food, thus manipulating the food web. Some of these economic metrics are closely tied to social sustainability metrics as well and try to account for the social welfare of a population. Overall, while physical tools can capture certain environmental and economic issues, too, they do not address economic issues from the same perspective as conventional economic analysis. Moreover, they do not capture most social issues.

    Economic markets do not usually directly value goods and services that ecological systems provide to human economies and societies. These ecosystem services include the uptake of carbon dioxide by plants and trees, purification of water by microorganisms, enrichment of soil through degradation of plant and animal materials, and rainfall that provides irrigation (see Constanza, et al., 1997). Also economists do not agree on the degree of substitutability between natural and man-made capital. This concept of substitutability means that natural capital such as 100 year old (“old forest”) trees used to build homes and furniture can be replaced by replanting fast-growing trees and provide the same value (Pearce, 1993). Technology also transforms the use of resources for instance by making them more readily available and more economic. An example of this is the use of “fracking” to produce natural gas from sources that were difficult to extract from a decade ago (see Module 10.2).

    Sustainability Indicators and Composite Indices

    There is no single indicator that can capture all aspects of sustainability within complex systems. When we speak of systems, we are referring to institutions, cities, regions, or nations. However, a group of indicators could be selected and analyzed under certain criteria that will better represent this type of system. An indicator represents a particular operational attribute of a system such as overall energy reduction, a GHG gas emissions inventory, what percentage of people commute by public transit, or percentage of people with a college degree. These are measured or observed at different times, locations, populations or combinations thereof. The Figure \(\PageIndex{1}\) represents the relationship between all these measures.

    A group of indicators can then be evaluated using a composite indicator/index (CI) or rating. CIs stand at the top of an information pyramid where primary data lies at the base, followed by analyzed data, then indicators, and topped by indices. A composite indicator is formed by the compilation of various individual indicators into one index based on an underlying model. (Nardo, et al., 2005). An example is the Leadership in Energy and Environmental Design (LEED) which is a green building certification system developed by the U.S. Green Building Council (USGBC). It accounts for a large variety of building attributes that contribute to a building being considered “sustainable” such as building materials, location, landscape, energy usage, access to alternative transportation and so on. The final result is a numerical rating for the building that is then associated with a certain certification level (Certified, Silver, Gold, Platinum). This kind of system is most widely accepted and valued when a peer-review is conducted to determine what weights should be given to each attribute. When the USGBC decided to update its rating system because it did not accurately reflect the values of its members, it underwent review through its various committees.

    Sometimes, when you have a lot of different measures that use different units you do not want to aggregate them together into one number. In this case, a multi-criteria assessment (MCA) can be used where constituent indicators are not aggregated into a single index. Multi-criteria analysis (similar name, different context) can be used as a tool to establish weights for several criteria, without requiring that all data be converted into the same units (Hermann, 2007). There are several multi-criteria evaluation methods that can be used for this. These methods may either be data-driven (bottom-up) when high-quality data is available or theory driven (top-down) when data is available for only one of the aspects. A broader review of this can be found in Gasparatos, et al. (2008).

    Many industry sectors are developing frameworks or rating systems that provide ways to report and measure sustainability. Two examples are discussed here.

    The Global Reporting Initiative (GRI) provides a system for organizations to publish their sustainability performance. Its purpose is to provide transparency and accountability for stakeholders and to be comparable among organizations. It is developed in an international, multi-stakeholder process and it is continuously improved. An organization determines which indicators from among those proposed it will report. However, no overall index or scores are reported. There is also usually a narrative portion to the report (Global Reporting Initiative). The indicators are broken down in environmental, economic and social performance indicators. Each area has core indicators with some additional indicators that may be used based on the organization’s choice.

    The American Association of Higher Education (AASHE), is the lead organization in North America for sustainability in colleges and universities. One of their major projects has been the development of the Sustainability Tracking, Assessment and Rating System (STARS). This is a voluntary, self-reporting framework that is to be used to measure relative progress of universities and colleges as they work toward sustainability. STARS was developed using a collaborative process that involved input from many institutions. In 2008, a pilot study of 66 institutions was conducted to test the viability of the system and STARS version 1.0 was released in January 2010 with many schools reporting by January 2011. The credits are given in three categories of equal weight – education and research; operations; planning, administration and engagement. Each credit is given a weight based on the extent to which the credit contributes to improved environmental, financial and social impacts, and whether there are educational benefits associated with the achievement of this credit and the breadth of that impact. The result is a composite indicator, with transparent individual scoring. Schools participating in STARS will use an on-line reporting tool which makes the results publicly available. Depending on the total points achieved, a level of achievement is be assigned. The STARS rating will be good for three years but a school may choose to update annually. See 11.3.3 for an example of this reporting.

    Examples of How an Index is Developed

    Krajnc and Glavic (2005) developed a composite sustainable development index (ICSD) to track economic, environmental and social performance of company. Economic, environmental, and social sub-indices were calculated from normalized indicators within each sector. To calculate normalized indicators, the indicators for each sector, which typically have different units, were divided by the value in time (year) with its average value of all the time in the years measured. Alternatively, they can be normalized by using maximum and minimum values or target values. The Analytic Hierarchy Process was used to determine the weights of the environmental indicators. This is a multi-attribute decision model. The steps are:

    1. Setting the problem as a hierarchy with the top being the objective of the decision and lower levels consist of the criteria used at arriving at the decision.
    2. Pair-wise comparisons between two indicators.
    3. Use of a consistency ratio to check the consistency of each judgment.
    4. Step-by-step procedure of grouping various basic indicators into the sustainability sub-index.
    5. Sub-indices are combined into the composite sustainable development index.

    The economic, environmental and social measures that were used in this model are as follows:

    Economic Environmental Social
    Sales Total Energy Consumption No. of occupational accidents
    Operating profit Water Consumption No. of non-profit projects
    Investment capital and expenditures Production mass No. of odor complains
    Net earnings Carbon dioxide, nitrous oxides, sulfur dioxides, dust emissions No. of noise complaints
    Research and Development costs Wastewater No. of dust complaints
    Number of employees Waste for disposal No. of neighbor complaints
    Hazardous waste

    Table \(\PageIndex{2}\)

    An analytical tool, called COMPLIMENT, was developed to provide detailed information on the overall environmental impact of a business (Hermann, 2007). This tool integrates the concepts of life cycle assessment, multi-criteria analysis and environmental performance indicators. The combinations of environmental performance indicators used depend on the organization and reflect the relevant parts of the production train. The method includes setting system boundaries, data collection, calculation of potential environmental impacts and their normalization, aggregation of impacts using a multi-criteria analysis, the weights per impact category are multiplied by normalization potential impacts and the results can be added up for each perspective. The system boundary strives to be cradle-to-grave (from extraction of resources to disposal) although it may be a cradle-to-gate (from extraction of resources to completion of production) analysis.

    Adoption of any single group of tools means that a certain perspective will be more highly represented in the sustainability assessment. “The need to address the multitude of environmental, social, economic issues, together with intergenerational and intragenerational equity concerns” (Gasparatos, et al., 2008, p. 306) produces problems that none of the disciplinary approaches can solve separately. Combining the outputs of biophysical and monetary tools will result in a more comprehensive sustainability perspective. The result is that the choice of metrics and tools must be made based on the context and characteristics that are desired by the analysts (Gasparatos, et al., 2008). Using a composite indicator or a set of individual indicators presented together can overcome the problem of using a single metric to measure sustainability.

    Existing indicator-based sustainability assessments vary in the number of subsystems or assessment areas, the number of levels between subsystem and indicator, and whether they result in an index (compound indicator) of the state of the system and subsystems. These would include the ecosystem or environment, people or economy and society, and possibly institutions. The more subsystems assigned, the lower the weight given to the environmental portion. As more indicator systems are developed they become increasingly complex, yet there is a demand for a simple presentation that does not erase the complexity. A single indicator with true significance is not achievable, but by combining indicators into indices the results are more meaningful.

    Representing Results for Multi-Criteria Assessment

    Since measuring sustainability does not come down to a simple metric or few it is useful to use visualization techniques to display the results. One way to depict sustainability performance is to use a graphical view of progress, as shown in Figure \(\PageIndex{2}\) below for the GRI for universities. For each category a mapping of the scores was created. This appears as a hexagon indicating progress in each area for which points are achieved.

    Green Office Challenge
    Figure \(\PageIndex{2}\) Visualizing Results of Sustainability Assessments Hypothetical graphical representation of the Environmental Dimension of the GRI for universities. The red numbers indicate the percentage of points achieved within each sub-category within the category of environment. Source: D. Fredman adapted from Lozano (2006).

    Another example of visualizing sustainability is seen in a framework developed for universities to use (Troschinetz et al., 2007). Again, multidimensional sustainability indicators, each having an economic, environmental and social component are used. The categories are listed in Figure \(\PageIndex{3}\). Each indicator was examined using a sustainability indicator triangle where each corner is delineated as economic, environmental or social and the indicators are placed within to the triangle to reflect how well each measures those aspects.

    Sustainability Indicator Triangle
    Figure \(\PageIndex{3}\) Sustainability Indicator Triangle The thirteen sustainability indicators are placed according to how well each measures a dimension of sustainability, i.e. environmental, societal and economic. Source: C. Klein-Banai adapted from Troschinetz, et al. (2007).


    Measuring sustainability is difficult because of the interdisciplinary nature and complexity of the issues that this concern represents. Methods have been developed out of the different disciplines that are based in the ecological, economic, physical and social sciences. When approaching a measure of sustainability it is important to understand what you will use the results of that measure for, what the major concerns you want to address are, and the limits of the system you choose. Often it is more meaningful to measure progress of the entity you are examining – is it more sustainable than it was before? It is difficult to compare similar entities (countries, companies, institutions, even products) due to the complexity and variability in the data. Using visualization to represent the data is a helpful way to show the state of sustainability rather than trying to express it in one number or in a table of numbers.

    Footprinting: Carbon, Ecological, and Water

    Basic Concepts of Footprinting

    What is a common measure of the impact of an individual, institution, region or nation? This can be done by measuring the “footprint” of that entity. When discussing climate change and sustainability the concepts of carbon footprint and ecological footprint are often used. Understanding how these footprints are derived is important to the discourse as not all calculations are equal. These footprints can be calculated at the individual or household level, the institutional level (corporation, university, and agency), municipal level, sub-national, national or global. They are derived from the consumption of natural resources such as raw materials, fuel, water, and power expressed in quantities or economic value. The quantity consumed is translated into the footprint by using conversion factors generally based in scientific or economic values.

    What is Your Carbon Footprint?

    There are many personal calculators available on the internet. Here are a few to try:

    • EPA Household Emissions Calculator
    • Ecological Footprint
    • Earth Day Network Footprint
    • Cool Climate Network (UC Berkeley)
    • Carbon Footprint

    This chapter will discuss three types of footprints – ecological, carbon and water – and the methodologies behind them. Although efforts have been made to standardize the calculations comparisons must be approached with caution. Comparing individual, institutional or national footprints that are calculated by the same method can be helpful in measuring change over time and understanding the factors that contribute to the differences in footprints.

    Ecological Footprint


    The Merriam-Webster Dictionary defines footprint as:

    1. an impression of the foot on a surface;
    2. the area on a surface covered by something

    Similarly, the ecological footprint (EF) represents the area of land on earth that provides for resources consumed and that assimilates the waste produced by a given entity or region. It is a composite index (see Module 10.2) that represents the amount of biologically productive land and water area required to support the demands of the population in that entity or region The EF is beneficial because it provides a single value (equal to land area required) that reflects resource use patterns (Costanza, 2000). The use of EF in combination with a social and economic impact assessment can provide a measure of sustainability’s triple bottom line (Dawe, et al., 2004). It can help find some of the “hidden” environmental costs of consumption that are not captured by techniques such as cost-benefit analysis and environmental impact (Venetoulis, 2001). Using the ecological footprint, an assessment can be made of from where the largest impact comes (Flint, 2001).

    Next, we will discuss the how an EF is calculated.


    The ecological footprint methodology was developed by William Rees and Mathis Wackernagel (1996), and consists of two methodologies:

    1. Compound calculation is typically used for calculations involving large regions and nations and is shown in Figure Compound Calculation Steps for Ecological Footprint Analysis. First, it involves a consumption analysis of over 60 biotic resources including meat, dairy produce, fruit, vegetables, pulses, grains, tobacco, coffee, and wood products. That consumption is then divided by biotic productivity (global average) for the type of land (arable, pasture, forest, or sea areas) and the result represents the area needed to sustain that activity. The second part of the calculation includes energy generated and energy embodied in traded goods. This is expressed in the area of forested land needed to sequester CO2 emissions from both types of energy. Finally, equivalence factors are used to weight the six ecological categories based on their productivity (arable, pasture, forest, sea, energy, built-up land). The results are reported as global hectares (gha) where each unit is equal to one hectare of biologically productive land based on the world's average productivity. We derive sub-national footprints based on apportioning the total national footprint between sub-national populations. The advantage of this method is that it captures many indirect of effects of consumption so the overall footprint is more accurate.
    2. Component-based calculation resembles life-cycle analysis in that it examines individual products and services for their cradle-to-grave resource use and waste, and results in a factor for a certain unit or activity. The footprint is typically broken down into categories that include energy, transportation, water, materials and waste, built-up land, and food. This method is better for individuals or institutions since it accounts for specific consumption within that entity. However, it probably under-counts as not all activities and products could practically be measured or included. It also may double-count since there may be overlap between products and services.
    Compound Calculation Steps for Ecological Footprint Analysis
    Figure shows the compound calculation steps for ecological footprint analysis. Source: C. Klein-Banai.
    What the Results Show

    When looking at the sub-national level, it is useful to be able to examine different activities that contribute to the footprint such as energy, transportation, water, waste, and food. In both types of calculations, there is a representation of the energy ecological footprint. We utilize conversion factors that account for direct land use for mining the energy source and the land required to sequester any carbon emitted during combustion, construction, or maintenance of the power source. It should be noted that no actual component-based calculations have been done for nuclear power. The practice has been to consider it the same as coal so as to account for it in some way. A discussion of the merits of this method can be found in Wackernagel et al. (2005).

    Transportation is another activity that can be examined at the sub-national level. The transportation footprint maybe considered part of the energy footprint, or separately, but is basically based on the energy consumption for transportation. It may also include some portion of the built-up land.

    The hydroprint, or water-based footprint, measures the amount of water consumed in comparison to the amount of water in the land catchment system for the geographical area being footprinted. It can represent whether the entity is withdrawing more or less water than is naturally supplied to the area from rainfall.

    The wasteprint, or waste-based footprint, is calculated using commonly used component-based factors that have been calculated and compiled in a number of publications and books. Food production requires energy to grow, process and transport, as well as land for growing and grazing. The factors are derived using the compound calculation for a certain geographical area. See 11.3.1 for an example of this kind of ecological footprint analysis. This kind of analysis can show us how a nation, region, organization, or individual uses the planets resources to support its operation or life style, as well as what activities are the primary contributors to the footprint. In the next section, we will look at some national footprints.

    Ecological Footprint Comparisons
    Ecological Footprints of Select Nations
    Figure \(\PageIndex{5}\) Ecological Footprints of Select Nations Graph shows the ecological footprints of select nations. The bars show average EF in global hectares per person for each nation. Each color on the bar represents the different types of land. Source: © 2010 WWF ( Some rights reserved. Living Planet Report, 2010 , figure under CC BY-SA 3.0 License

    The Living Planet Report prepared by the World Wildlife Fund, the Institute of Zoology in London, and Wackernagel’s Global Footprint Network reports on the footprints of various nations. Figure Ecological Footprints of Select Nations displays the footprint of several nations as shown in the report. The bars show average EF in global hectares per person for each nation. Each color on the bar represents the different types of land. Here we see that the United Arab Emirates has the largest footprint of 10.2 gha per person, with the majority of its footprint due to carbon (same as energy land described above). Whereas Latvia has the lowest footprint displayed at 6.0 gha per person, with the majority of its footprint due to forestland.

    United States’ Ecological Footprint
    Figure shows the United States’ Ecological Footprint compared to the global average. Source: © 2010 WWF ( Some rights reserved. Living Planet Report, 2010, figure under CC BY-SA 3.0 License

    Figure \(\PageIndex{6}\) shows the national footprint in 2007 of the United States as 7.99 gha per person both with a bar display and with specific metrics on the right that show the exact footprint and the United States’ ranking among all nations in the report (e.g. carbon is 5.57 gha and ranks 3rd largest overall). The bar to the left expresses the world average. The United States’ footprint of 7.99 gha stands in contrast to the earth's global biocapacity of 1.8 gha per person. Globally, the total population’s footprint was 18 billion gha, or 2.7 gha per person. However, the earth’s biocapacity was only 11.9 billion gha, or 1.8 gha per person. This represents an ecological demand of 50 percent more than the earth can manage. In other words, it would take 1.5 years for the Earth to regenerate the renewable resources that people used in 2007 and absorb CO2 waste. Thus, earth’s population used the equivalent of 1.5 planets in 2007 to support their lives.

    Carbon Footprint

    Since climate change (see Chapter Climate and Global Change) is one of the major focuses of the sustainability movement, measurement of greenhouse gases or carbon footprint is a key metric when addressing this problem. A greenhouse gas emissions (GHG) inventory is a type of carbon footprint. Such an inventory evaluates the emissions generated from the direct and indirect activities of the entity as expressed in carbon dioxide equivalents (see below). Since you cannot manage what you cannot measure, GHG reductions cannot occur without establishing baseline metrics. There is increasing demand for regulatory and voluntary reporting of GHG emissions such as Executive Order 13514, requiring federal agencies to reduce GHG emissions, the EPA’s Mandatory GHG Reporting Rule for industry, the Securities and Exchange Commission’s climate change disclosure guidance, American College and University Presidents’ Climate Commitment (ACUPCC) for universities, ICLEI for local governments, the California Climate Action Registry, and numerous corporate sustainability reporting initiatives.

    Scoping the Inventory

    The first step in measuring carbon footprints is conducting an inventory is to determine the scope of the inventory. The World Business Council for Sustainable Development (WBCSD) and the World Resource Institute (WRI) defined a set of accounting standards that form the Greenhouse Gas Protocol (GHG Protocol). This protocol is the most widely used international accounting tool to understand, quantify, and manage greenhouse gas emissions. Almost every GHG standard and program in the world uses this framework as well as hundreds of GHG inventories prepared by individual companies and institutions. In North America, the most widely used protocol was developed by The Climate Registry.

    The GHG Protocol also offers developing countries an internationally accepted management tool to help their businesses to compete in the global marketplace and their governments to make informed decisions about climate change. In general, tools are either sector-specific (e.g. aluminum, cement, etc.) or cross-sector tools for application to many different sectors (e.g. stationary combustion or mobile combustion).

    Scopes of a Greenhouse Gas Emissions Inventory
    Figure shows the three scopes of a greenhouse gas emissions inventory. Source: New Zealand Business Council for Sustainable Development, The challenges of greenhouse gas emissions: The “why” and “how” of accounting and reporting for GHG emissions (2002, August), figure 3, p. 10.

    The WRI protocol addresses the scope by which reporting entities can set boundaries (see Figure \(\PageIndex{4}\)). These standards are based on the source of emissions in order to prevent counting emissions or credits twice. The three scopes are described below:

    • Scope 1: Includes GHG emissions from direct sources owned or controlled by the institution – production of electricity, heat or steam, transportation or materials, products, waste, and fugitive emissions. Fugitive emissions are due to intentional or unintentional release of GHGs including leakage of refrigerants from air conditioning equipment and methane releases from farm animals.
    • Scope 2: Includes GHG emissions from imports (purchases) of electricity, heat or steam – generally those associated with the generation that energy.
    • Scope 3: Includes all other indirect sources of GHG emissions that may result from the activities of the institution but occur from sources owned or controlled by another company, such as business travel; outsourced activities and contracts; emissions from waste generated by the institution when the GHG emissions occur at a facility controlled by another company, e.g. methane emissions from landfilled waste; and the commuting habits of community members.

    Depending on the purpose of the inventory the scope may vary. For instance, the EPA mandatory reporting requirements for large carbon dioxide sources require reporting of only Scope 1 emissions from stationary sources. However, many voluntary reporting systems require accounting for all three scopes, such as the ACUPCC reporting. Numerous calculator tools have been developed, some publicly available and some proprietary. For instance many universities use a tool called the Campus Carbon Calculator developed by Clean Air-Cool Planet, which is endorsed by the ACUPCC. Numerous northeastern universities collaborated to develop the Campus Carbon Calculator and the calculator has been used at more than 200 campuses in North America. It utilizes an electronic Microsoft Excel workbook that calculates estimated GHG emissions from the data collected.


    GHG emissions calculations are generally calculated for the time period of one year. Figure \(\PageIndex{5}\) shows the steps for reporting GHG emissions. It is necessary to determine what the baseline year is for calculation. This is the year that is generally used to compare future increases or decreases in emissions, when setting a GHG reduction goal. The Kyoto Protocol proposes accounting for greenhouse gas emissions from a baseline year of 1990. Sometimes calculations may be made for the current year or back to the earliest year that data is available.

    Steps for Preparing a GHG Emissions Report
    Figure shows the required steps to take when preparing a GHG emissions report. Source: C. Klein-Banai

    Next, the institutional or geographic boundaries need to be defined. Also, the gases that are being reported should be defined. There are six greenhouse gases defined by the Kyoto Protocol. Some greenhouse gases, such as carbon dioxide, occur naturally and are emitted to the atmosphere through natural and anthropogenic processes. Other greenhouse gases (e.g. fluorinated gases) are created and emitted solely through human activities. The principal greenhouse gases that enter the atmosphere because of human activities are:

    • Carbon Dioxide (CO2): Carbon dioxide is released to the atmosphere through the combustion of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of non-combustion reactions (e.g. manufacture of cement). Carbon dioxide is sequestered when plants absorb it as part of the biological carbon cycle.
    • Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also come from farm animals and other agricultural practices and the degradation of organic waste in municipal solid waste landfills.
    • Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, and combustion of fossil fuels and solid waste.
    • Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e. Chlorofluorocarbons (CFCs), hydrochlorofluorocarbon (HCFCs), and halons). CFCs and HCFCs are gases comprised of chloride, fluoride, hydrogen, and carbon. Halons are elemental gases that include chlorine, bromine, and fluorine. These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”)

    Each gas, based on its atmospheric chemistry, captures different amounts of reflected heat thus contributing differently to the greenhouse effect, which is known as its global warming potential. Carbon dioxide, the least capture efficient of these gases, acts as the reference gas with a global warming potential of 1. Table \(\PageIndex{3}\) shows the global warming potential for the various GHGs.

    Gas GWP
    CO2 1
    CH4 21
    N2O 310
    HFC-23 11,700
    HFC-32 650
    HFC-125 2,800
    HFC-134a 1,300
    HFC-143a 3,800
    HFC-152a 140
    HFC-227ea 2,900
    HFC-236fa 6,300
    HFC-4310mee 1,300
    CF4 6,500
    C2F6 9,200
    C4F10 7,000
    C6F14 7,400
    SF6 23,900

    Table \(\PageIndex{6}\) Global Warming Potentials Source: C. Klein-Banai created table using data from Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, section 2.10.2

    GHG emissions cannot be easily measured since they come from both mobile and stationary sources. Therefore, emissions must be calculated. Emissions are usually calculated using the formula:

    \[ A\ \times \ F_{g}\ =\ E \label{1} \]

    where A is the quantification of an activity in units that can be combined with emission factor of greenhouse gas g (Fg) to obtain the resulting emissions for that gas (Eg).

    Examples of activity units include mmbtu (million British Thermal Units) of natural gas, gallons of heating oil, kilowatt hours of electricity, and miles traveled. Total GHG emissions can be expressed as the sum of the emissions for each gas multiplied by its global warming potential (GWP). GHG emissions are usually reported in metric tons of carbon dioxide equivalents (metric tons CO2-e):

    \[ GHG\ =\ \sum_{g}\ E_{g}'GWP_{g} \label{2} \]

    Eg is usually estimated from the quantity of fuel burned using national and regional average emissions factors, such as those provided by the US Department of Energy’s Energy Information Administration.

    Emission factors can be based on government documents and software from the U.S. Department of Transportation, the U.S. Environmental Protection Agency (EPA), and the U.S. Department of Energy, or from specific characteristics of the fuel used – such as higher heating value and carbon content. Scope 3 emissions that are based on waste, materials, and commuting are more complex to calculate. Various calculators use different inputs to do this and the procedures are less standardized. See Case Study: Comparing Greenhouse Gas Emissions, Ecological Footprint and Sustainability Rating of a University for an example of these kinds of calculations.

    Greenhouse gas emissions inventories are based on standardized practice and include the steps of scoping, calculating, and reporting. They are not based on actual measurements of emissions, rather on calculations based on consumption of greenhouse gas generating materials such as fossil fuels for provision of energy and transportation or emissions from waste disposal. They can be conducted for buildings, institutions, cities, regions, and nations.

    Carbon Footprint Comparisons

    Comparison of carbon footprints reveal interesting differences between countries, particularly when compared to their economic activity. The World Bank tracks data on countries and regions throughout the world as part of their mission to “fight poverty…and to help people help themselves and their environment” (World Bank, 2011). Table Gross Domestic Product (GDP) and Emissions for Select Regions, 2007 shows the results for GHG emissions and gross domestic product for various regions of the world. It is interesting to note that the United States’ emissions per capita (19.34 mt e-CO2) are more than four times the world average. The United States’ economy makes up one fourth of the world GDP.

    Country Name CO2 Emissions (metric tons) CO2 Emissions (metric tons per capita) GDP (current US$ Millions) GDP per capita (current US$)
    East Asia and Pacific (all income levels) 10,241,229 4.76 $11,872,148 $5,514
    Europe and Central Asia (all income levels) 6,801,838 7.722 $20,309,468 $23,057
    Latin America and Carribean (all income levels) 1,622,809 2.87 $3,872,324 $6,840
    Latin America and Carribean (developing only) 1,538,059 2.75 $3,700,320 $6,610
    Least developed countries: UN classfication 185,889 0.23 $442,336 $553
    Middle East and North Africa (all income levels) 1,992,795 5.49 $1,924,470 $5,304
    South Asia 1,828,941 1.20 $1,508,635 $991
    Sub-Saharan Africa (all income levels) 684,359 0.86 $881,547 $1,102
    United States 5,832,194 19.34 $14,061,800 $46,627
    World 30,649,360 4.63 $55,853,288 $8,436

    Table \(\PageIndex{7}\) Gross Domestic Product (GDP) and Emissions for Select Regions, 2007Table shows the GDP and emissions for select regions in 2007. Source: C. Klein-Banai created table using data from The World Bank, "World Development Indicators"

    Water Footprint

    The water footprint of production is the volume of freshwater used by people to produce goods, measured over the full supply chain, as well as the water used in households and industry, specified geographically and temporally. This is slightly different from the hydroprint described above which simply compares the consumption of water by a geographic entity to the water that falls within its watershed. If you look at the hydrologic cycle (see module Water Cycle and Fresh Water Supply), water moves through the environment in various ways. The water footprint considers the source of the water as three components:

    • Green water footprint: The volume of rainwater that evaporates during the production of goods; for agricultural products, this is the rainwater stored in soil that evaporates from crop fields.
    • Blue water footprint: The volume of freshwater withdrawn from surface or groundwater sources that is used by people and not returned; in agricultural products this is mainly accounted for by evaporation of irrigation water from fields, if freshwater is being drawn.
    • Grey water footprint: the volume of water required to dilute pollutants released in production processes to such an extent that the quality of the ambient water remains above agreed water quality standards.

    The water footprint of an individual is based on the direct and indirect water use of a consumer. Direct water use is from consumption at home for drinking, washing, and watering. Indirect water use results from the freshwater that is used to produce goods and services purchased by the consumer. Similarly, the water footprint of a business or institution is calculated from the direct and indirect water consumption.

    Water Footprint of Production of Select Countries
    Figure \(\PageIndex{6}\) Water Footprint of Production of Select Countries Graph shows the water footprint of production of select countries. Source: © 2010 WWF ( Some rights reserved. Living Planet Report, 2010, figure under CC BY-SA 3.0 License

    Figure \(\PageIndex{6}\) shows the water footprint of production for several countries as a whole. In this report, due to lack of data, one unit of return flow is assumed to pollute one unit of freshwater. Given the negligible volume of water that evaporates during domestic and industrial processes, as opposed to agriculture, only the grey water footprint for households and industry was included. This figure does not account for imports and exports it is only based on the country in which the activities occurred not where they were consumed.

    In contrast, the water footprint of a nation accounts for all the freshwater used to produce the goods and services consumed by the inhabitants of the country. Traditionally, water demand (i.e. total water withdrawal for the various sectors of economy) is used to demonstrate water demand for production within a nation. The internal water footprint is the volume of water used from domestic water resources; the external water footprint is the volume of water used in other countries to produce goods and services imported and consumed by the inhabitants of the country. The average water footprint for the United States was calculated to be 2480m3/cap/yr, while China has an average footprint of 700m3/cap/yr. The global average water footprint is 1240m3/cap/yr. As for ecological footprints there are several major factors that determine the water footprint of a country including the volume of consumption (related to the gross national income); consumption pattern (e.g. high versus low meat consumption); climate (growth conditions); and agricultural practice (water use efficiency) (Hoekstra & Chapagain, 2007).

    Using average water consumption for each stage of growth and processing of tea or coffee, the “virtual” water content of a cup can be calculated (Table \(\PageIndex{8}\)). Much of the water used is from rainfall that might otherwise not be “utilized” to grow a crop and the revenue from the product contributes to the economy of that country. At the same time, the result is that many countries are “importing” water to support the products they consume.

    Drink Preparation Vital Water Content (mL/cup)
    • Standard cup of coffee
    • Strong coffee
    • Instant coffee
    • 140
    • 200
    • 80
    • Standard cup of tea
    • Weak tea
    • 34
    • 17

    Table \(\PageIndex{8}\) Virtual Water Content of a Cup of Tea or CoffeeTable shows the virtual water content for a cup of tea or coffee. Source: C. Klein-Banai created table using data from Chapagain and Hoekstra (2007). alt="Virtual Water Content of a Cup of Tea or Coffee" longdesc="Table shows the virtual water content for a cup of tea or coffee."

    To learn more about other countries’ water footprints, visit this interactive graph. To calculate your own water footprint, visit the Water Footprint Calculator.


    Footprinting tools can be useful ways to present and compare environmental impact. They are useful because they can combine impacts from various activities into one measure. However, they have limitations. For instance, in a carbon footprint or greenhouse gas emissions inventory, many of the “conventional” environmental impacts such as hazardous waste, wastewater, water consumption, stormwater, and toxic emissions are not accounted for, nor are the impacts of resource consumption such as paper, food, and water generally measured. Perhaps most importantly, certain low-carbon fuel sources (e.g. nuclear power) that have other environmental impacts (e.g. nuclear waste) are neglected. Finally, the scope of the emissions inventory does not include upstream emissions from the manufacture or transport of energy or materials. This suggests that there is a need to go beyond just GHG emissions analyses when evaluating sustainability and include all forms of energy and their consequences.

    The ecological footprint can be misleading when it is looked at in isolation, for instance with an urban area, the resources needed to support it will not be provided by the actual geographic area since food must be “imported” and carbon offset by natural growth that does not “fit” in a city. However, cities have many other efficiencies and advantages that are not recognized in an ecological footprint. When looked at on a national level it can represent the inequities that exist between countries.

    It is interesting to contrast the water and ecological footprints, as well. The water footprint explicitly considers the actual location of the water use, whereas the ecological footprint does not consider the place of land use. Therefore it measures the volumes of water use at the various locations where the water is appropriated, while the ecological footprint is calculated based on a global average land requirement per consumption category. When the connection is made between place of consumption and locations of resource use, the consumer's responsibility for the impacts of production at distant locations is made evident.

    Case Study: Comparing Greenhouse Gas Emissions, Ecological Footprint and Sustainability Rating of a University

    How do different measures of sustainability compare when looking at one institution? This case study compares these different measures for the University of Illinois at Chicago (UIC). Located just southwest of downtown Chicago, UIC has 13 colleges serving 27,000 students and 12,000 employees, with over 100 buildings on 240 acres (97 hectares) of land. The activities of the faculty, staff and students and the buildings and grounds have an impact on the sustainability of the institution. This case study will look at the results of the greenhouse gas emission inventory, ecology footprint, and sustainability rating.

    Greenhouse Gas Emissions Inventory
    Figure \(\PageIndex{7}\) Greenhouse Gas Emissions Inventory UIC's Greenhouse gas emissions profile for FY2004-2010, using the regional mix for purchased electricity. Source: C. Klein-Banai

    Figure \(\PageIndex{7}\) displays UIC's GHG emissions profile for seven years. The emissions were calculated using the Campus Carbon Calculator developed by the not-for-profit organization, Clean Air-Cool Planet. While this tool has a number of limitations it has been used by many of the over 670 colleges and universities who are signatory to the American College and University Presidents Climate Commitment (ACUPCC) to simplify the emissions inventory profile. The tool is also recommended by the ACUPCC as a standard method of emissions calculation for United States universities. It is based on the World Resources Institute (WRI) and World Business Council for Sustainable Development (WBSCD) Greenhouse Gas (GHG) Protocol Initiative that developed GHG emissions inventory standards. UIC's emissions were calculated using the regional average electricity sources for the electric grid servicing the Chicago area. However, until August of 2009, UIC purchased electricity from Commonwealth Edison which has a much lower greenhouse gas emissions factor due to the high percentage of nuclear power in the Chicago region.

    UIC operates two combined heat and power plants. However, the university has increasingly lowered its production of electricity from natural gas by purchasing more electricity through block purchases (for defined amounts of electricity for a certain period of time) due to the relatively low cost of purchasing electricity as compared to self-generating. This strategy has increased UIC's emissions as the regional mix has a fair amount of coal-powered plants providing electricity. Neverthless, a downward trend in emissions is beginning in spite of the increased electricity purchases between 2009 and 2010. This may be due to overall reduction in energy consumption on campus, which is reducing the GHG emissions.

    Figure \(\PageIndex{8}\) illustrates the relative contribution to UIC's 2010 emissions profile, with 77 percent of emissions coming from buildings (power plants, purchased electricity, and other on-campus stationary, i.e. natural gas supply to the buildings), 20 percent due to transportation (campus fleet , commuting to campus, and air travel), and less than one percent for emissions due to waste sent to the landfill (which generates methane).

    Breakdown of UIC's Greenhouse Gas Emissions
    Figure shows the breakdown of UIC's greenhouse gas emissions inventory for the fiscal year 2010, in metric tons of carbon dioxide equivalents (mt CO2-e). Total emissions: 354,758 mt CO2-e. Source: C. Klein-Banai

    UIC's total emissions for fiscal year 2010 were 354,758 mt CO2-e, which amounts to 13.14 mt CO2-e per full-time equivalent student enrolled. Table \(\PageIndex{9}\) compares UIC's emissions to those of the city of Chicago, state of Illinois, and the United States.

    Entity GHG Emissions, Million MT CO2 e- Most Recent Year Reported
    US 6,633.20 2009
    Illinois 374.9 2003
    Chicago 36.2 2005
    UIC 0.4 2010

    Table \(\PageIndex{9}\) Comparison of GHG EmissionsSources: C. Klein-Banai created table using data from UIC Climate Action Plan, Chicago Climate Action Plan, U.S. EPA.

    An Ecological Footprint Analysis (EFA) was conducted using data from fiscal year 2008, including much of the same data used for the GHG emissions inventory. In addition, water, food, recycling, and built-up land data were used to calculate the number of global hectares required to provide the resources and absorb the waste and GHG emissions produced to support UIC's activities. The results are displayed in Table \(\PageIndex{10}\). The total footprint was 97,601 global hectares, on a per capita basis this is equivalent to 2.66 gha/person. This is in contrast to about 8.00 gha/person nationally in the United States, although one must use caution in making comparisons because the scope and methodology of the analysis differ.

    Category Global Hectares Percent
    Energy 70,916 72.7%
    Transportation 12,293 12.6%
    Water 139 0.1%
    Materials and waste 11,547 11.8%
    Built-up land 172 0.2%
    Food 2,533 2.6%
    Total Global Hectares 97,601 100%

    Table \(\PageIndex{10}\) UIC's Ecological Footprint Using FY2008 DataComposite Indicator: Sustainability Tracking, Assessment and Rating System. Source: C. Klein-Banai.

    The STARS system (see module Sustainability Metrics and Rating Systems) was used to rate UIC. The university received 39.1 points, for a Bronze rating. The points break down into the categories shown in Table \(\PageIndex{11}\). There are three main categories of points – Education & Research; Operations; and Planning, Administration & Engagement. Within each of the categories there are sub-categories such as Curriculum, Climate, and Coordination & Planning. Within those sub-categories there are specific strategies that address them, with varying amounts of points that depend on the assessed weight of each strategy. Each category's individual percentage score is weighted equally to the others. In addition, four innovation strategies are available for which an institution can receive one point. These points are not attributed to a particular category.

    Points Received Possible % Per Category Weight
    Education and Research 38.61% 33.33/100
    Co-Curricular Education 11.75 18.00
    Curriculum 18.89 55.00
    Research 7.97 27.00
    Operations 23.78% 33.33/100
    Buildings 0.23 13.00
    Climate 1.75 16.50
    Dining Services 1.25 8.50
    Energy 3.44 16.50
    Grounds 1.00 3.25
    Purchasing 1.76 7.50
    Transportation 5.71 12.00
    Waste 6.89 12.50
    Water 1.75 10.25
    Planning, Administration, and Engagement 54.91% 33.33/100
    Coordination and Planning 15.00 18.00
    Diversity and Affordability 13.50 13.75
    Human Resources 19.75 19.75
    Investment 0 16.75
    Public Engagement 6.66 31.75
    Innovation 0 4.00

    Table \(\PageIndex{11}\) STARS Points Received by UIC by CategorySource: C. Klein-Banai with data from STARS

    This reporting system shows that UIC's strengths lie in the areas outside of operations, which are what is measured with an EFA or GHG emissions inventory. Most points were gained for Planning, Administration & Engagement. This rating system can be used to identify specific areas that can be targeted for advancing sustainability initiatives in a much broader realm than the other two metric allow. This case study demonstrates the different types of information and sustainability tracking that can be done using different types of measures of sustainability. Whether you use one measure or several depends on the purpose and scope of the sustainability reporting.

    Food Miles


    Efforts to explore the impacts of the items on our dinner tables led to the broad concept of food miles (the distance food travels from production to consumption) as being a quick and convenient way to compare products. With increasing globalization, our plates have progressively included food items from other continents. Previously it would have been too expensive to transport these products. However, changes to agricultural practices, transportation infrastructure, and distribution methods now mean that people in the United States can start the day with coffee from Brazil, have a pasta lunch topped with Italian cheeses, snack on chocolate from Côte d'Ivoire, and end with a dinner of Mediterranean bluefin tuna and Thai rice. However, the globalization that has led to increased availability of these products comes with associated costs, such as the emission of greenhouse gases and other pollutants, increased traffic congestion, lack of support for local economies, less fresh food, and decreased food security. Therefore, the concept of measuring food miles was meant to provide an easy comparison of the relative impacts of our food choices.

    Many individuals, groups, and businesses today measure or calculate food miles. But, when Andrea Paxton, a U.K.-based environmental activist, coined the term in the 1990s the concept of food miles was intended to encompass more than simply a distance. The point was to broaden awareness that our food choices have consequences that are often not apparent. Consumers frequently do not know the histories behind their food purchases, and markets often cannot supply the information because of the many production processes and distribution methods used.

    While the distance food travels does determine some of the environmental, social, and economic impacts, there can be other hidden consequences not so easily measured. Exploration of the utility of food miles in the general sense of knowing the impacts of our purchasing decisions has resulted in a broadening awareness of the complexity of globalization. Although consumers can use the easy-to-compare numbers representing food miles, that metric cannot reflect all of the impacts of food purchasing decisions.

    Calculating Food Miles

    In some cases it is easy to use food miles, such as comparing two watermelons grown using the same methods and both transported by truck to your store. However, many of our food products contain components with different origins. In that case, food miles are calculated as a weighted average to create a single number that takes into consideration the weight and distance of each item. For example, to calculate the food miles for a simple fruit salad that contains only apples, bananas, and honey, you need to know the distance that each ingredient traveled to reach your market and the relative amount of each product.

    Food Miles for Fruit Salad
    Figure \(\PageIndex{9}\) Food Miles for Fruit Salad The various ingredients in this simple fruit salad travel different distances to Illinois' supermarkets. Source. D. Ruez adapated from TUBS, akarlovic, Fir0002, and Abrahami

    Most of our food from supermarkets is marked with a country or state of origin. That alone is usually enough to get an estimate of the distance, especially if the location can be narrowed down by finding out the part of the country or state that most commonly produces the product. If the fruit salad in Figure \(\PageIndex{10}\) is being made in Chicago, Illinois, and the apples are from the state of Washington, the likely origin is in the center part of the state. The travel distance is approximately 2,000 miles (3,219 km). Bananas from Costa Rica traveled about 2,400 miles (3,862 km) to Chicago, and there are honey producers only 160 miles (257 km) from Chicago. A simple average of the miles the ingredients traveled would not take into account that the fruit salad probably would not contain equal amounts of the three items. If the recipe called for 2 pounds (.9 kg) of apples, 2 pounds (.9 kg) of bananas, and a ¼ pound (.1 kg) of honey, the miles would be weighted toward the distances traveled by the fruit: 2080 food miles per pound of fruit salad (or 3,347 km/kg of fruit salad).


    The benefits of using food miles in evaluating food choices match the three main categories that represent sustainability: environmental, social, and economic. All methods of transporting food over long distances, and most methods used to transport over short distances, involve fossil fuels. Burning of fossil fuels creates greenhouse gases, which contribute to climate change. Using fossil fuels also results in the emission of other gases and particulates that degrade air quality. Longer transportation distances intensify traffic congestion, resulting in lost productivity, and increase the need for more extensive infrastructure (such as more highways) that negatively impact the environment by increasing the amount of impervious cover and by requiring more natural resources. Increased roadways also encourage sprawl, leading to more inefficient development patterns. Finally, traffic congestion and air pollution from driving contribute to an estimated 900,000 fatalities per year worldwide.

    Use of food miles is often tied to locavore movements, which emphasizes consumption of locally-grown food products. Local food is usually fresher, with harvesting waiting until produce is ripe, and has less processing and fewer preservatives. Many people think locally-grown food tastes better, but others chose to be a locavore because it strengthens local cultural identity or because the safety of the food is being controlled by people who also consume the products themselves. Eating local foods also promotes food security because availability and price of imported foods is more dependent on fluctuating fuel costs and sociopolitical conflicts elsewhere.

    The production of food in developing countries, and the subsequent exporting of those products, has several types of impacts. The environmental burden of soil degradation, water depletion, and others, are imposed on developing countries, while more prosperous countries enjoy the benefits. This can be especially problematic because some developing countries do not have the policies to require, or the resources to implement, more environmentally-friendly food production practices. In particular, the low prices paid to food producers in developing countries do not include sufficient funds, or requirements, for practices to preserve or restore ecosystem quality. Moreover, developing countries disproportionately suffer malnutrition, yet the success of large-scale transport of food encourages cultivation of products to be exported instead of planting nutritious foods to be self-sustaining.

    Some businesses are embracing the basic concepts of food miles because transporting food over shorter distances uses less fuel, and is therefore cheaper. Additionally, food that covers longer distances usually requires more packaging, which adds to the cost. By focusing on local foods, local economies are supported. This has led to clearer labeling of food products, giving consumers the ability to make more informed decisions about their purchases.


    Although the concept of food miles is useful, it has been heavily criticized for being too simplistic. For example, all miles are not created equally. The consumption of fuel varies by the mode of transportation and the amount being moved. If you compare the consumption required to move one pound of a product, ocean freighters are the most efficient of the common methods, followed by trains, trucks, and finally planes. When a combination of transportation methods is used, making a comparison with food miles becomes even more complex. This is especially a problem because most of us drive a personal vehicle to get our groceries. That means that it may be more efficient (from a total fuel consumption perspective) to drive 1 mile (1.6 km) to a local supermarket who imports beef from Australia, than to drive 40 miles (64 km) to visit a market selling locally-produced beef.

    Food miles also do not take into consideration the variables of production before the products are transported. Growing outdoors requires different amounts of energy input than greenhouses. A commonly cited example is that of tomatoes; heating greenhouses to grow tomatoes in the United Kingdom consumes much more energy than growing tomatoes in warm Spain and importing them. Use of chemical fertilizers and pesticides affect environmental quality and production levels differently than organic farming. Because soil quality varies, locally-grown foods, in some cases, require more of the chemical additives. Some areas may have newer equipment, better climate, increased access to water, or other factors that determine the overall efficiency of food production. Growing rice in deserts or oranges in the Arctic would have more environmental impacts than the transportation of those products from locales where they can be grown more efficiently (from both an environmental and economic perspective). Understanding these production variables is critical because several recent studies have suggested that as much as 80% of greenhouse-gas generation from food consumption comes from the production phase.

    There are also benefits to globalization and increased transport of food. There is now more widespread access to a broader range of food products. This can lead to increased appreciation for other cultures and greater international cooperation. Long-distance transport of food products can also provide jobs to developing nations by giving them access to larger, more prosperous markets internationally. Jobs and economic incentives from food production are some of the few widespread opportunities for developing countries, and these may lead to growth in other economic areas.

    Criticism of the use of food miles can be unfairly disapproving of products that travel long distances. However, simple calculations of food miles have also been said to underrepresent the importance of travel distances. Most food is transported with some packaging, and that packaging also requires energy input for its production and transport. Because products that move shorter distances usually have less packaging, the difference in calculated food miles may underestimate the actual environmental impact. Local foods also require less energy and resource consumption because of reduced need for transportation infrastructure, chemical additives and preservatives, and refrigeration.

    The impacts during the production phase also vary between types of foods, which can also result in underestimates of the impacts. Production of meats, especially red meats, requires large amounts of land to generate the crops needed for animal feed. Because not all energy is passed from feed to the animal, using meats for our food is inefficient from an energy perspective. It takes over 8 pounds of grain to feed a cow enough to generate 1 pound of weight gain. That grain must be grown on land that can long longer produce food directly for human consumption. The amount of land required to produce animal feed is known as ghost acres. Ghost acres also extend to the areas required to provide the fuel, water, and other resources needed for animal feed, and for the overall support of animals1. While some other meats such as pork, poultry, and especially fish, use proportionally less feed, there are other concerns about the environmental impacts of diets with large amounts of meat.

    Confined animal feeding operations (CAFOs), high-density animal farms, have become the primary source of livestock for meat in the U.S., Europe, and many other countries. The technological innovations employed in these operations have increased the speed and volume of meat production, but have raised health concerns. Antibiotics and hormones used increasingly on animals in CAFOs may be passed on to humans during consumption, even though there is currently no way of knowing a safe level of those substances in our diets. The overuse of antibiotics in CAFOs also results in antibiotic-resistant pathogens. In addition to the impacts from the ghost acres, there are other ecological impacts such as pollution from massive amounts of concentrated manure. Although the distance meat is transported has an environmental impact, the other concerns are more significant.

    Confined Animal Feeling Operations (CAFOs)
    Figure \(\PageIndex{10}\) Confined Animal Feeding Operations (CAFOs)This image shows a CAFO for cattle. CAFOs have raised health concerns for human consumption of the meat produced in them. Source: eutrophication & hypoxia


    The ongoing investigations of food miles have affected businesses, groups, and individuals in various ways. As mentioned above, paying closer attention to the distance food travels can be a good business strategy because fuel costs money. Centralization of processing and distribution centers in the United States has resulted in a relative frequent occurrence of shipping produce thousands of miles only to end up in supermarkets back near its origin. In many cases the initial savings from building fewer centralized facilities is exceeded in the long-term by the continual shipping costs. As a result, some retailers are encouraging outside scrutiny of their habits, because it can result in increased profits. At the other extreme, the rise in food miles in some cases is driven entirely by money. Fish caught offshore Norway and the United Kingdom, for example, is sent to China for cheaper processing before being returned to European markets.

    An awareness of the impact of food miles has led to many groups advocating local foods. Local farmers' markets have appeared and expanded around the United States and elsewhere, providing increased access to fresh foods. Community-supported agriculture programs create share-holders out of consumers, making them more personally invested in the success of local economies, while farmers gain some financial security. Campaigns by community groups are influencing retailers and restaurants by scrutinizing the food-purchasing decisions. The reciprocal is also true as retailers and restaurants advertise their sustainability efforts. See Resources for examples of local farmers' markets in Illinois.

    Illinois Farmer's Market
    Figure \(\PageIndex{11}\) Illinois Farmer's Market Colorful produce at an Illinois farmer's market. Source: Maycomb Paynes

    Yet, there are challenges to the implementation of food miles as a concept. Suppliers, such as individual farmers, might opt for the reliable annual purchase from a mass-distributor. Consumers might make decisions solely on the sticker price, not knowing the other impacts, or consumers might know the impacts but choose the immediate economic incentive. Some of these challenges can be addressed by education. This can include efforts such as eco-labeling – labels, often by third parties, that independently attest to the environmental claims of products. This can influence some consumers, but larger buyers like school systems and restaurant chains may require other incentives to change purchasing practices. The source of these incentives, or alternatively, regulations, might come from government agencies, especially those with desires to support local economies. However, there is no consensus regarding who should be evaluating and monitoring food miles.


    The criticisms of food miles are valid, and work is continually being done incorporate the many factors that more completely show the environmental impacts of transporting food. This can be a time consuming process, and the many variables are usually not readily available to consumers. A frozen pizza might contain many types of ingredients from various areas that are transported to individual processing plants before being assembled in another location and forwarded to distribution centers before being shipped to stores. Even if this process is eventually simplified, eating decisions should not be made solely on the basis of food miles, which cannot account for the variations in transportation and production methods or the social and economic impacts.

    This does not mean that food miles are never a useful tool. When comparing similar products (e.g., onions to onions) with other similar externalities (e.g., production and transportation methods), food miles provide a convenient way for consumers to begin to make informed decisions about their purchases. Even though food transportation is a relatively small portion of the overall impact of our food consumption, changes to any phase of the process can have a positive additive effect and make a real contribution to environmental health. Moreover, most of the benefits for using food miles can likewise apply to many of our non-food purchases, with allowances for some of the same drawbacks. Additionally, the discussion could be expanded to include other kinds of decisions, such as where to live in relation to location of job, and where to take a vacation. In general, the concept of food miles reflects the need to understand how hidden influences generate environmental, social, and economic impacts.

    Environmental Performance Indicators


    Because there are so many types of environmental problems, there are many projects designed to address these concerns and likewise many methods to assess them. Collectively, the methods for assessing environmental impactsand the uses of natural resources (both living and non-living) are called environmental performance indicators. Generally, performance indicators are used in fields ranging from marketing and economics to education and legal studies to measure a project's progress and/or success. Some indicators can evaluate the actions of a single individual, while others are broad enough to reflect the efforts of entire nations or even the globe. Specifically, environmental performance indicators (EPIs) examine environmental issues such as pollution, biodiversity, climate, energy, erosion, ecosystem services, environmental education, and many others. Without these EPIs, the success or failure of even the most well-intentioned actions can remain hidden.

    Because of the diversity of observational scales and topics, not all EPIs are useful in all scenarios. However, all EPIs should indicate whether the state of the environment is changed positively or negatively, and they should provide a measure of that change. An EPI is also more meaningful if it can quantify the results to facilitate comparison between different types of activities. But before an EPI is selected, targets and baselines must be clearly articulated. Vague targets are difficult to evaluate, and the results may be uninformative. The EPI selected must use indicators that are definitively linked to the targets, are reliable and repeatable, and can be generated in a cost and time efficient manner.

    To evaluate an activity, an EPI needs to include information from up to four types of indicators: inputs, outputs, outcomes, and impacts. Inputs are the natural resources or ecosystem services being used. Outputs are the goods or services that result from that activity. While outputs can often be quantified, outcomes typically cannot be and instead represent environmental, social, and economic dimensions of well-being. In some cases it is useful to think of outcomes as why an output was sought; however, outcomes can also be unanticipated or unwanted effects of an output. Impacts refer to the longer-term and more extensive results of the outcomes and outputs, and can include the interaction of the latter two indicators.

    For example, coal can be an input for an electricity-generating plant because we need the output (electricity) to turn on lights in our homes. Two outcomes would include the ability to read at night because of the electricity and the visible air pollution from the power plant smoke stacks. An impact of being able to read more can be a better-educated person, while an impact of the greenhouse gas emissions from burning coal is increased potential for global climate change. This is a simplistic example which does not include the majority of relevant indicators (inputs, outputs, outcomes, and impacts) for a complete and more meaningful analysis.

    We can then evaluate each of the indicators. Is the input (coal) an appropriate choice? Is there enough for the practice of burning it to continue? Are there problems, such as political instability that could interrupt continued access? Does the output (electricity) sufficiently address the problem (in this case, energy for turning on lights)? Is the output produced and delivered in a timely manner? Is it provided to the appropriate consumers and in a quantity that is large enough? Does the output create the desired outcome (being able to read at night)? Does it also result in unwanted outcomes (air pollution)? Do the outcomes result in long-term impacts (such as life-long learning or decade-long climate change) that are widespread?

    Note that outcomes and impacts can be either positive or negative. The strength of an EPI lies in its ability to look at the bigger picture and include multiple variables – particularly with regard to the impacts. However, whether an impact is considered meaningful depends on the values and perspectives of the individuals and groups involved. Judgment plays a role because of the difficulty in comparing completely different impacts. How do you compare life-long learning and climate change in the above example about the use of coal?


    Monitoring the impacts of both short-term and long-term activities with EPIs allows decision makers to make changes that result in performance with lesser environmental impacts. In some cases, changes can be made to ongoing projects, or the results of an EPI can be used for publicity if the performance data indicate the activity is environmentally-sound. In other cases, the EPI establishes a performance benchmark against which other projects are measured, or the results are used in the strategic planning phase while projects are in development. In this way, past successes and failures can both be incorporated into future plans.

    Use of EPIs requires production of multiple data points. A single application of an EPI does not mean much until placed into a larger context. For example, an EPI might evaluate the impact of your city's recycling efforts (see Figure \(\PageIndex{12}\)), but that result can be difficult to interpret without additional data that can be presented in multiple ways:

    • Absolute values: Is the impact greater or less than that of other cities? How does the total cost of the recycling program compare?
    • Normalized values: How does the per person impact compare to another city, country, business, etc.? What is the amount of aluminum recycled per dollar spent on recycling?
    • Trends: Is your city improving, or is the progress your city sees in recycling better than that that of other cities? This could be asked of either absolute or normalized data: Is the total amount of aluminum recycled in your city increasing? Is the per-person amount of aluminum recycled in your city increasing?
    Municipal Solid Waste Recycling Rates
    Figure \(\PageIndex{12}\) Municipal Solid Waste Recycling Rates Municipal solid waste recycling rates in the United States from 1960-2007. Source: EPA

    Major EPI Areas

    Most EPIs focus on one or a few categories of environmental problems and do not attempt to be all-inclusive methods of evaluating sustainability. A few of the more common categories are briefly described below.

    Biodiversity is the number and variety of forms of life, and can be calculated for a particular tree, an ecosystem, a nation, or even the planet. Food, fuel, recreation, and other ecosystem services are dependent on maintaining biodiversity. However, biodiversity is threatened by overuse and habitat destruction (see Figure Endangered Animals). Because the actual number of species alive is not known, biodiversity indicators often use proxy data. These include patterns of habitat preservation and resource use, because they are the primary factors influencing biodiversity. The better-known groups of organisms, such as birds and mammals, are also monitored for a direct count of biodiversity, but vertebrates are a tiny proportion of life and cannot accurately reflect changes in all species.

    Endangered Animals
    Figure \(\PageIndex{13}\) Endangered Animals Illustration shows the number of endangered animals in each country of the world. Source: World Atlas of Biodiversity

    Wood is harvested for timber and fuel, but forests are also cleared for agricultural fields and housing developments. Such deforestation frequently leads to rapid soil erosion and extinctions. Cutting of forests also results in changes to the water cycle, altering precipitation patterns and rates, and nutrient cycles, such as the release of carbon dioxide into the atmosphere. At the same time as deforestation takes its toll in places, trees are being planted elsewhere. Developed countries are increasing their forested areas, but this is commonly being done at the expense of developing countries, which are exporting their wood (see Figure \(\PageIndex{13}\)). Forestry indicators in EPIs include the annual change in forested areas, but can be broken down into the types of forests because each has different environmental impacts. Another indicator is the use of non-sustainable wood resources. Tree farms and some harvesting methods provide renewable supplies of wood, while clear-cutting tropical forests does not. Irresponsible wood harvesting produces negative results for ecosystem health.

    Deforestation in Haiti
    Figure \(\PageIndex{14}\) Deforestation at the Haiti/Dominican Republic Border Satellite photograph show deforestation of Haiti (on the left) at the border with the Dominican Republic (on the right). Deforestation on the Haitian side of the border is much more severe. Source: NASA

    Air, water, and land pollution directly, and adversely, impacts human and ecosystem health. It also has economic consequences from the damage of natural resources and human structures. In many cases the level of pollutants can be measured either in the environment or at the point of emissions. Additional indicators include whether pollution monitoring even occurs, to what extent legal maximum levels are enforced, and whether regulations are in place to clean up the damage. Visit the EPA's MyEnvironment application to learn more about environmental issues in your area.

    Greenhouse gas emissions and ozone depletion are results of air pollution, but are frequently placed in a separate category because they have global impacts regardless of the source of the problem. Levels of greenhouse gases and ozone-depleting substances in the atmosphere can be measured directly, or their impacts can be measured by looking at temperature change and the size of the ozone hole. However, those methods are rarely part of EPIs because they do not assign a particular source. Instead, EPIs include the actual emissions by a particular process or area.

    Examples of EPIs

    There are dozens of EPIs that can be used to evaluate sustainability. Below are two examples of multi-component methods that allow comparisons at a national level, which is necessary for promoting many types of systemic change.

    Environmental Sustainability Index

    The environmental sustainability index (ESI) was created as a joint effort of Yale and Columbia universities in order to have a way to compare the sustainability efforts and abilities of countries. Visit the ESI website for more information such as maps and data. First presented in 2000 at the World Economic Forum, the ESI has quickly gained popularity because it aids decision-making by providing clear comparisons of environmental statistics. The basic assumption of the ESI is that sustainable development, the use of resources in a way to meet societal, economic, and environmental demands for the long-term, requires a multi-faceted approach. Specifically, the ESI uses 76 variables to create 21 indicators of sustainability.

    The indicators cover five categories, with each description below indicating the condition that is more sustainable:

    • environmental systems – maintaining and improving ecosystem health
    • reducing environmental stress – reducing anthropogenic stress on the environment
    • reducing human vulnerability – having fewer negative impacts on people from the environment
    • capacity to respond to environmental challenges – fostering social infrastructures that establish ability and desire to respond effectively to environmental challenges
    • global stewardship efforts – cooperating with other countries to address environmental problems.

    The ESI scores range from 0, least sustainable, to 100, most sustainable, and is an equally-weighted average of the 21 individual indicators. The highest-ranked countries in 2005 (Finland, Norway, Uruguay, Sweden, and Iceland) all had in common abundant natural resources and low human-population densities. At the other extreme, the lowest-ranked countries (North Korea, Iraq, Taiwan, Turkmenistan, and Uzbekistan) had fewer natural resources, particularly when compared per capita, and have made policy decisions often against their own long-term best interests. However, it is important to note that most countries do not excel, or fail, with regard to all 21 indicators; every nation has room for improvement. Each country will also have its own environmental priorities, attitudes, opportunities, and challenges. For example, the United States scores high in the capacity to respond to environmental challenges, but low in actually reducing environmental stress.

    ESI scores have sparked some healthy competition between nations; no one wants to be seen as underperforming compared to their peers. After the pilot ESI rankings in 2000 and the first full ESI rankings in 2002, Belgium, Mexico, the Philippines, South Korea, and the United Arab Emirates, all initiated major internal reviews that resulted in the initiation of efforts to improve environmental sustainability. Because ESI data are presented not only as an overall average but also as 21 independent indicators, countries can focus their efforts where most improvement could be made. Countries dissatisfied with their rankings have also begun to make more of their environmental data accessible. Initial rankings by ESI score had missing or estimated data in many cases, but by making more data available, more accurate overall assessments are possible. For example, the Global Environmental Monitoring System Water Program, an important source of water quality information, had data contributions increase from less than 40 countries to over 100 as a result of the ESI.

    Several similar ranking methodologies have emerged from the ESI. They vary in the number and type of variables included and indicators produced. Some also calculate an overall average by weighting some indicators more than others. However, they all share the same 0-100 scale and have individual indicators that allow targeted improvement of the overall scores.

    Emergy Performance Index

    One drawback of the ESI is that the indicators measure items as different as percentage of endangered animals, recycling rates, government corruption, and child mortality rates. The scope of the variables has been criticized because they may not be comparable in importance, and many others could be added. The term, emergy, is a contraction of EMbodied enERGY. The emergy performance index (EMPI) differs in omitting the social variables, and instead creates a single unit that can be used to describe the production and use of any natural or anthropogenic resource.

    The first step of calculating EMPI is to inventory all material and energy inputs and outputs for all processes and services. Every process and service is then converted to its equivalent in emergy. The amounts of emergy of each type are summed. There are several possible ways to group emergy by type and to combine the data, but generally the goal is to create either a measure of emergy renewability (as an indicator of stress on the environment) or emergy sustainability (which combines renewability with the total productivity and consumption or emergy).

    Calculating the emergy equivalents of materials and energy can be done easily with a conversion table, but creating the table can be a challenge. Burning coal releases an amount of energy that is easy to measure and easy to convert to emergy. However, determining the amount of energy required to create coal is nearly impossible. Similarly, how can you quantify the emergy conversion factor for objects like aluminum or for ecosystem services like rainfall? It is difficult, but possible, to place a dollar value on those objects and services, but assigning an energy equivalent is even more tenuous. While converting everything to a common unit, emergy, simplifies comparisons of diverse activities and processes like soil erosion and tourism, there are concerns about the accuracy of those conversions.


    There are no perfect measures of sustainability, and different indicators can sometimes give conflicting results. In particular this happens when perspectives on the most important components of sustainability, and the methods to address them, differ. Therefore, it is often useful to examine the main characteristics of several Environmental Performance Indicators to find the one most appropriate for a particular study. As an example, ESIs, EMPIs, and ecological footprinting (discussed in a previous section) are compared below.

    Ecological footprinting (EF) has units that are the easiest to understand – area of land. Both EF and EMPI employ only a single type of unit, allowing for use of absolute variables and permitting quantitative comparisons. However, EF does not use multiple indicators to allow for focused attention on impacts. EMPI can also be used as scaled values (such as the proportion of emergy from renewable sources), in the same manner as ESI. However, ESI combines multiple units of measurements, which can provide a more holistic perspective, but at the same time leads to concerns about combining those data.

    Of the three, ESI and EMPI take into account wastefulness and recycling, and only ESI includes the effects of all emissions. But while ESI includes the most variables, it is the most complex to calculate; the simplest to calculate is EF.

    Because ESI includes social and economic indicators, it can only compare nations (or in some cases, states or other levels of governments). EF and EMPI are effective at comparing countries, but can also be used at scales from global down to individual products.

    All three of the EPIs compared here can be useful, but each has their limitations. Additionally, there are scenarios where none of these are useful. Specific environmental education projects, for example, would require different types of performance indicators.

    Case Study: UN Millenium Development Goals Indicators

    In 2000 the United Nations created the Millennium Development Goals (MDGs) to monitor and improve human conditions by the year 2015. This framework was endorsed by all UN member nations and includes goals in eight areas: hunger/poverty, universal primary education, gender equity, infant mortality, maternal health, disease, global partnerships, and environmental sustainability.

    Each of the MDGs on basic human rights has one or more targets, with each target having specific indicators for assessment. Most of the targets have a baseline year of 1990 and specify an achievement rate. For example, one target is to halve the proportion of people suffering from hunger. By specifying a proportion, targets can be monitored separately at national, regional, and global levels. Visit the interactive map at MDGMonitor to track and monitor progress of the Millennium Development Goals.

    The underlying principle of the MDGs is that the world has sufficient knowledge and resources to implement sustainable practices to improve the life of everyone. Annual progress reports suggest that this principle may be realistic only for some targets. The targets within environmental sustainability are the implementation of national policies of sustainable development, increased access to safe drinking water, and improvements to urban housing. There are success stories: efforts to increase availability of clean water have resulted in improvements faster than expected. However, not all indicators are showing improvement. Impacts of climate change are accelerating, and risks of physical and economic harm from natural disasters are increasing. Moreover, these impacts and risks are concentrated in poorer countries – those least able to handle the threats. Overall, results are mixed.

    The worldwide rate of deforestation is still high but has slowed. Large-scale efforts to plant trees in China, India, and Viet Nam have resulted in combined annual increases of about 4 million hectares of forests since 2000. Unfortunately, that is about the same rate of forest loss in South America and Africa each. Globally, the net loss of forest from 2000 to 2010 was 5.2 million hectares per year, down by a third from the 1990s.

    The world will likely meet the target of halving the proportion of people without access to clean water, with the majority of progress made in rural areas. By 2008 most regions exceeded or nearly met the target levels. The exceptions were Oceania and sub-Saharan Africa, which had only 50% and 60% respectively of their populations with access to improved water sources. Those regions will almost certainly miss the target. They, and most other developing regions, will also miss the target of halving the proportion of the population lacking improved sanitation facilities. In fact, the total number of people without such access is expected to grow until at least 2015.

    From 1990 to 2007, emissions of carbon dioxide rose in developed regions by 11%; in developing regions, which have much higher rates of population growth, emissions increased by 110%. While most indicators have shown either progress or minimal additional harm, carbon dioxide emissions stand out as one of the significant failures in achieving global sustainability.

    Efforts to preserve biodiversity have made only minimal progress. One target was to have 10% of each of the world's terrestrial ecosystem types protected by 2010; only half were. The proportion of key biodiversity areas protected stagnated in the 2000s, after showing faster improvements in the 1970s-1990s. As a result, the number of birds and mammals expected to go extinct in the near future has increased.

    The environmental sustainability target for urban housing was meant to significantly improve the lives of 100 million slum-dwellers by 2020. This target differed from most others not only by using a later date of 2020, but by lacking a specified proportion of the population. Setting a target as an absolute value for the entire globe obscures the progress in individual countries, so this criterion may be revisited. From 1990 to 2010, the proportion of slum-dwellers decreased from 46% to 33%. However, during the same time, the number of people living in slums increased from 657 million to 828 million. Over 200 million slum-dwellers achieved access to clean water and improved sanitation facilities, so the target was met. However, it is widely acknowledged that the target was set too low.

    Even as we continue to strive toward the MDGs 2015 target date, it is also necessary to think beyond them. Changing demographics will drive shifts in the global economy and the use of resources. Increased effects of climate change will result in greater volatility, while technological developments can open new opportunities. In light of these changes, evaluation of the MDGs must assess their utility after 2015. Should the general framework stay in place, should it be modified with new approaches, or should it be replaced with something fundamentally different?



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    Review Questions

    1. What is the difference between data and an index?
    2. What is the major challenge in measuring sustainability?
    3. Give three general categories of indicators that are used for measuring sustainability and provide one example of each.
    4. Why is it important to have experts provide input to rating systems?
    5. Choose a calculator from the box and calculate your own footprint. How does it compare to the national or global average? What can you do to reduce your footprint?
    6. Discuss what kind of inequities the various footprints represent between nations and the types of inequities.
    7. How might the “food print” of a vegetarian differ from a carnivore?
    8. What are some of the problems with comparing food miles for a cheeseburger to those for a vegetarian salad?
    9. Why might food producers in isolated but prosperous areas (like Hawaii or New Zealand) argue against the use of food miles?
    10. Do you think increased reliance on food miles is good or bad for rural areas in developing countries? Explain your decision.
    11. What is the difference between energy and emergy?
    12. In what way(s) is ESI a better method of assessing sustainability than EF and EMPI?
    13. The ESI creates indicators in five areas. In which of the areas do you think the indicators are the least reliable?
    14. Why do EPIs require multiple data points to be useful?


    Carrying Capacity

    The maximum population that a given environment can sustain.


    All living organisms and non-living things that exist and interact in a certain area at the same time.

    Ecosystem Goods and Services

    An essential service an ecosystem provides that supports life and makes economic activity possible. For example, ecosystems clean air and water naturally, recycle nutrients and waste generated by human economic activity.


    The amount of energy of one kind (solar) that has been used directly or indirectly (through a transformation process) to make a service or a product as one type and it is expressed in units of (solar) emjoule.


    The unit of emergy or emergy joule. Using emergy, sunlight, fuel, electricity, and human service can be put on a common basis by expressing each of them in the emjoules of solar energy that is required to produce them. If solar emergy is the baseline, then the results are solar emjoules (abbreviated seJ). Sometimes other baselines such as coal emjoules or electrical emjoules have been used but in most cases emergy data are given in solar emjoules.


    The degree of disorder in a substance, system or process as in the second law of thermodynamics that states that the make-up of energy tends to change from a more-ordered state to a less-ordered state, whereby increasing entropy.


    The maximum work that can be extracted from a system as it moves to thermodynamic equilibrium with a reference state.


    A variable equal to an operational representation of an attribute of a system.

    Indicator-Based Systems

    Systems that use quantitative measures of economic progress, social welfare, or environmental activity that can be interpreted to explain the state of that system. Examples of these are gross domestic product, greenhouse gas emissions, and the unemployment rate.

    Maximum Sustainable Yield (MSY)

    An outgrowth of carrying capacity and the goal is to reach the maximum amount of resource extraction while not depleting the resource from one harvest to the next.

    Narrative Assessments

    Descriptive documentation of a program, plan, or project.

    Quantitative Data

    Information that can be quantified numerically such as tons of waste, gallons of gasoline, and gallons of wastewater.


    The ability of an ecological community to change in response to disturbance and the degree or time needed for that system that provides desirable to go back to its original state.


    Relating to or resulting from the influence that humans have on the natural world.


    From creation to disposal; throughout the life cycle.

    Ecological Footprint (EF)

    Represents the area of land on earth that provides for resources consumed and assimilates the waste produced by a given entity.

    Global Warming Potential (GWP)

    Each gas, based on its atmospheric chemistry, captures different amounts of reflected heat thus contributing differently to the greenhouse effect contributing to its GWP. Carbon dioxide, the least capture efficient of these gases, acts as the reference gas with a global warming potential of 1.

    Gross Domestic Product

    The sum of gross value added by all resident producers in the economy plus any product taxes and minus any subsidies not included in the value of the products. It is calculated without making deductions for depreciation of fabricated assets or for depletion and degradation of natural resources.


    Removed from the atmosphere

    Triple Bottom Line

    Accounting for ecological and social performance in addition to financial performance)

    Emergy (EMbodied energy)

    The unit of energy into which any resource, product, or process can be converted to simplify comparisons between diverse items.

    Emergy Performance Index (EMPI)

    Value produced by converting all materials and processes to amounts of energy in order to evaluate renewability and sustainability.

    Environmental Sustainability Index (ESI)

    A composite value produced by including ecological, social, economic, and policy data.

    Environmental Performace Indicators (EPI)

    Any of the ways in which environmental outcomes and/or impacts can be assessed.


    Long-term and more widespread results of an activity.


    The specific resources or services used by an activity.


    The short-term results of an activity.


    The goods and services being created by an activity, and the manner and degree in which they are delivered.