Ecological Footprint
What Is the Ecological Footprint?
The Ecological Footprint is rooted in the fact that all renewable resources come from the earth. It accounts for the flows of energy and matter to and from any defined economy and converts these into the corresponding land/water area required for nature to support these flows. The Ecological Footprint is defined as "the 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 the land and water is located."1 It compares actual throughput of renewable resources relative to what is annually renewed. Non-renewable resources are not assessed, as by definition their use is not sustainable.
The total “footprint” for a designated population’s activities is measured in terms of ‘global hectares.’ A global hectare (acre) is one hectare (2.47 acres) of biologically productive space with an annual productivity equal to the world average. Currently, the biosphere has approximately 11.2 billion hectares of biologically productive space corresponding to roughly one quarter of the planet’s surface. These biologically productive hectares include 2.3 billion hectares of ocean and inland water and 8.8 billion hectares of land. The land space is composed of 1.5 billion hectares of cropland, 3.5 billion hectares of grazing land, 3.6 billion hectares of forest land, and 0.2 billion hectares of built-up land. These surfaces represent the sum total of biologically productive hectares we rely on for our survival. They represent the earth’s natural capital, and their annual yield represents our annual natural capital income. 
Ecological Overshoot Demonstrated
Dividing the 11.2 billion hectares available by the global population indicates that there are on average 1.8 bioproductive hectares per person on the planet. The 2004 Living Planet Report indicates that the actual usage was 13.5 billion global hectares or 2.2 hectares per person – more than a 20% overshoot.2 The overshoot result indicates that our annual draw down of natural capital is liquidating natural capital income, as well as reducing natural capital itself ( see Natural Capital and Income). Such an overshoot is ecologically unsustainable. Time series of the global Ecological Footprint indicate that human activities have been in an overshoot position for approximately three decades, and the overshoot is increasing over time.
Empirically demonstrating that ecological overshoot is now occurring by a significant margin is a major contribution to our understanding that we are exceeding sustainable ecological scale on a global level, and by roughly how much. The implications of these results are even more urgent when we realize that the Ecological Footprint is likely an underestimate of the actual demands we place on the earth’s ecosystems.3
The Footprint of Different Activities
This measure can also be presented in terms of the types of products or services provided by the global hectares, for example, in terms of goods from crop lands, animal products, fish, forest products, built up areas, and energy and water use. Such analyses identify which areas are placing the greatest strains on ecosystems, and can help set policy priorities. Growth in animal products and energy use, especially of fossil fuels, are two areas that are rapidly increasing these strains.
The Footprint of Nations
Ecological Footprint looks at the total amount of global hectares that are required to support a particular population, regardless of whether those hectares are within the national borders where that population lives. It does this by considering the net consumption of the population (or activity) of interest, subtracting the global hectares used for export from those used for imports and production. The Footprints of individual nations vary considerably, from highs of near 10 hectares per capita for such countries as the United Arab Emirates, the United States and Kuwait, to lows less than 1 hectare per capita for such countries as Haiti, Somalia and Afghanistan.
By comparing the Footprint measure with the actual bioproductive capacity of individual nations it is possible to determine if that country is in an ecological deficit (using more than it has) or has an ecological reserve. The US, Japan, the UK, and the United Arab Emirates are all in ecological deficit, using more global hectares than their own land mass provides. Countries with an ecological reserve include Australia, Mongolia, and Gabon.
Some, but not all, countries can run ecological deficits by appropriating bioproductive hectares from other countries. However, the global deficit represented by the 20% overshoot cannot be compensated for as there is only one planet available. These data highlight the intimate connection between ecological sustainability and just distribution, and the contribution of international trade to inequities in national Footprints.
Sound Methodology
The methodology for the Ecological Footprint is detailed but not overly complex. Data inputs are from publicly available national, international and private organizations. A variety of accounting assumptions are made, but they are explicit and always entail a conservative bias. Weaknesses in this pioneering endeavor have been acknowledged, many have been corrected, and others are being addressed with further research.
A Policy Tool: The Footprint as an Indicator
One of the many strengths of the Ecological Footprint is its immediate intuitive appeal. Along with its reasonable and continuously improving methodology, this appeal has led to its widespread use in a variety of settings, addressing national, regional, municipal and even individual footprints. The measure itself simply describes the size of the footprint for a particular population or activity. But its implication for policy and planning purposes has been recognized, leading to its use by several countries and municipalities to implement and monitor their sustainable development agendas. It has proven a useful research tool to explore the footprint of specific activities such as different modes of transportation or methods of farming. There is also an annual global footprint report that provides a useful overview across many specific areas.4
Limitations
The Ecological Footprint is not a precise measure of ecological sustainability. While it is perhaps the best estimate to date, it is important to recognize its limitations. In general, the Footprint underestimates the impact of human activities on the biosphere. Any applications of the Footprint methodology must keep this perspective in mind. Because it focuses on renewable resources, the Footprint provides limited information about most non-renewable resources and their impact on ecosystems (with the exception of fossil fuel impacts which it partially addresses).
The concept of “global hectares” of world average bioproductivity is useful for looking at issues related to global Footprint. But individual applications refer to specific locations where there is an impact. These local areas may have bioproductivity rates different from the global average; where available, local data can be used. Another limitation is that the approach allows only general types of bioproductive areas to be identified (e.g. cropland, forests, etc). Specific ecosystems within these areas are not addressed. These limitations do not invalidate the Footprint, but do underline the importance of interpreting any specific application with these limitations in mind.
Relation to ScaleThe Ecological Footprint is the closest empirical measure now available to estimate maximum sustainable scale (see Sustainable Scale). It captures the bioproductive capacity that is required to support a given level of material throughput, with current practices and systems of organization. Maximum sustainable scale relates the physical amount of material throughput in economic activities relative to the biophysical limits of the ecosystems which are involved as sources or sinks. Ecological Footprint differs only in that it involves the throughput involved in all human activities. Most, but not all, of these activities are economic ones.
The Ecological Footprint is connected to many of the other approaches to thinking about and measuring scale:
- Footprint and biocapacity is a way to measure historical human carrying capacity. Most Carrying Capacity studies try to answer a hypothetical quesiton: how many people could live on the planet. The Footprint indicates how much of the planet was occupied by people. This is an historical question that can be empirically determined rather than conjecturing on future possibilities.
- Footprint analysis provides a means of assessing the impact of population, affluence (consumption) and technology identified in the The IPAT Equation.
- Footprint was used extensivly in last update of the Limits to Growth to give a summary report of human demand on nature.
- Footprint translates material flows in areas necessary to support these flows (see Material Flow Analysis).
- Footprint translates some of the principles of The Natural Step into a resource account (particularly principle 1 and 3).
- Footprint is an ecological economics tool. (see Ecological Economics Perspectives).
Ecological Footprint could also be useful in making socio-political decisions regarding optimal scale (see Sustainable Scale). Optimal scale is an ecological and socio-political target for sustainability. The Footprint accounting process could be used to describe a rough, if cautious, target of optimal scale. The global target would have to be some level of global hectares below those available, to ensure overshoot does not inadvertently occur. By identifying who is contributing how much to the size of a footprint, it can help us understand the potential tradeoffs in setting optimal scale at different levels. It could also be used to identify throughput targets for various nations, industries, or regions.
Future Directions
Efforts are underway to standardize and refine the methodology underlying the Footprint, and to incorporate areas or issues not currently captured.5 This continuous attention to methodological and conceptual rigor is a positive move and promises to increase the usefulness of this sustainability indicator. The intuitive appeal of the Footprint is another asset, leading to its adoption for many projects. For applications of the Footprint to sustainable scale issues, it would be wise to keep in mind that this measure likely provides an underestimate of ecological impact.
References and Links
3"Global Footprint Network Homepage." Global Footprint Network. www.footprintnetwork.org
4"Living Planet Report 2004." World Wildlife Foundation. http://www.panda.org/downloads/general/lpr2004.pdf
5"Global Footprint Network Homepage." Global Footprint Network. www.footprintnetwork.orgtake from http://www.sustainablescale.org/conceptualframework/understandingscale/measuringscale/ecologicalfootprint.aspx
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