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Introduction and definition
Conceived in the early nineties by William Rees and Mathis Wackernagel at the University of British Columbia, the ecological footprint is now widely used by scientists, businesses, governments, agencies, civil society organizations and individuals, working to monitor ecological resource use and advance sustainability.
The ecological footprint is a measure of human demand on the Earth's ecosystems. It compares human demand on nature with Earth‘s ecological capacity to regenerate resources and provide services. The ecological footprint represents the amount of biologically productive land and water area needed to produce the resources an individual, population or activity consumes and to absorb and render harmless the corresponding waste, given prevailing technology and resource management practices. This area can then be compared with the amount of productive area that is available to generate these resources and to absorb the waste.
Ecological footprint analysis calculates the combined demand for ecological resources, expressed as the global average area needed to support a specific human activity. Demand for resource production and waste assimilation are translated into a common area unit by dividing the total amount of a resource consumed by the yield per hectare, or dividing the waste emitted by the absorptive capacity per hectare. Yields are calculated based on various international statistics, primarily from the United Nations Food and Agriculture Organization.
An important component in footprint calculations, particularly for rich countries, is inclusion of the amount of land with new vegetation that would hypotheticallly take up carbon dioxide emissions (in contrast to land actually used for food or timber). In fact, a large part of human-produced carbon dioxide emissions are not taken up through photoshynthesis on land but are taken up by oceans, with about half accumulating in the atmosphere causing the increased greenhouse effect. In ecological footprint calculations, land and water area is scaled according to its biological productivity. This scaling makes it possible to compare ecosystems with differing bioproductivity and in different areas of the world in the same unit, a global hectare (gha). Six main land use types are considered in ecological footprint accounts: cropland, grazing land, fishing ground, forests for timber and fuelwood, forests for carbon dioxide uptake, and built-up land. For all land use types there is a demand on the area, as well as a supply of such an area.
Usually the ecological footprint of a population is calculated from a consumption perspective, i.e., it measures the land demanded by the final consumption of the residents of the country. This includes household consumption as well as their collective consumption of items, such as schools, roads, etc. Most ecological footprint studies and published reports refer to this perspective. However, the ecological footprint can also be calculated based on production. In this case, a country‘s primary production ecological footprint is the sum of the footprints for all resources harvested and all waste generated within the country‘s geographical borders. The difference between the estimates provided by these two perspectives corresponds to the balance between imports and exports.
Footprint results and use
Metrics such as the ecological footprint are a useful tool in the sustainability debate, since they allow us to give an attractive representation (in terms of hectares), easy to grasp, of the present use of natural resources.
For example, using an ecological footprint analysis, Wackernagel and his associates estimate how many planet Earths it would take to support humanity if everybody lived a given lifestyle. According to the Ecological Footprint Atlas 2009 (available at http://www.footprintnetwork.org/images/uploads/Ecological_Footprint_Atlas_2009.pdf), in 2006, humanity‘s total ecological footprint was 17.1 billion global hectares (gha); with world population at 6.6 billion people, the average person‘s footprint was 2.6 global hectares. The area of biologically productive land and water on Earth was estimated at approximately 11.9 billion hectares, or 1.8 gha per person. This overshoot of approximately 40 percent means that in 2006 humanity used the equivalent of 1.4 Earths to support its consumption. This is of course a metaphor since there is only one planet Earth. The result is largely due to the accounts of hypothetical land for taking up carbon dioxide emissions. Global comparisons also clearly show the inequalities of resource use worldwide.
Per capita ecological footprint is a means of comparing consumption and lifestyles. While an average inhabitant of Bangladesh or Nepal consumes 0.5 gha per year (in 2006), an average Chinese takes 1.8 gha and an average American 9.0 gha (Figure 1).
Ecological footprinting is now widely used around the globe as an indicator of environmental sustainability. Footprints can inform policy by examining to what extent a nation or a region or a city uses more (or less) than is available within its territory, or to what extent the nation's lifestyle would be replicable worldwide. It can also be a useful tool to educate people about carrying capacity and overconsumption, with the aim of influencing individual behavior. Ecological footprints may be used to explore the sustainability of individual lifestyles, goods and services, organizations, industry sectors, neighborhoods, cities, regions and nations. A number of NGO websites allow estimation of one's ecological footprint (http://www.footprintnetwork.org/en/index.php/GFN/page/personal_footprint/ or http://www.myfootprint.org/ ).
Figure 1: Ecological footprint by country
(Source: Ecological Footprint Atlas 2009)
Problems and concerns
The Global Footprint Network (www.footprintstandards.org.) developed the first set of ecological footprint standards in a facilitated public process in 2006, detailing communication and calculation procedures, and continues to work toward an accepted standardized methodology. The ecological footprint is an intuitively appealing indicator (easy to communicate and understand with a strong conservation message). The indicator is most effective, meaningful and robust at aggregate levels (national and above), but concerns have been raised regarding the use of the ecological footprint as a sustainability indicator. Many criticisms are related to the lack of consideration of aspects such as land degradation, biodiversity loss, toxicity to humans and ecosystems, etc. Also issues such as the distinction between intensive and extensive agriculture, accounting for multifunctionality in ecosystems and neglecting resource scarcity have been raised. It should be acknowledged that the use of natural resources entails a large number of different environmental impacts. One single indicator is unable to illustrate the complexity of these impacts and their interrelations, in particular, regarding burden shifting between different types of impacts. Moreover, two important issues are not properly addressed in EF calculations. First, how much land should be devoted to the maintenance of other ―wild‖ species? Second, why to express the issue of excessive carbon dioxide emissions in terms of hypothetical land required to absorb it? Therefore, sustainability assessment should not rely on the use of a single tool or indicator, but use a set of indicators covering different perspectives and dimensions of sustainability. See for instance the WWF‘s Living Planet Report (http://www.panda.org/about_our_earth/all_publications/living_planet_report/lpr_2008/ ). Ecological footprints may be a powerful and useful tool in this context.
- Best, A., S. Giljum, C. Simmons, D. Blobel, K. Lewis, M. Hammer, S. Cavalieri, S. Lutter and C. Maguire. 2008. Potential of the Ecological Footprint for monitoring environmental impacts from natural resource use: Analysis of the potential of the Ecological Footprint and related assessment tools for use in the EU‘s Thematic Strategy on the Sustainable Use of Natural Resources. Report to the European Commission, DG Environment.
- Ewing B., S. Goldfinger, A. Oursler, A. Reed, D. Moore, and M. Wackernagel. 2009. The Ecological Footprint Atlas 2009. Oakland: Global Footprint Network.
van den Bergh, J. and H. Verbruggen, 1999, Spatial sustainability, trade and indicators: an evaluation of the ‗ecological footprint‘, Ecological Economics, Vol. 29(1): 63-74.
- Wackernagel, M. and W. Rees. 1996. Our Ecological Footprint: Reducing Human Impact on the Earth. New Society Publishers.
- Wackernagel, M., N., Schulz, D. Deumling,, A. Callejas Linares, M. Jenkins, V. Kapos, C. Monfreda, J. Loh, N. Myers, R. Norgaard, and J. Randers. 2002. Tracking the ecological overshoot of the human economy. Proceedings of the National Academy of Sciences, Vol. 99, Issue 14, pages 9266-9271, July 9, 2002.