Picture a city totally enclosed by a transparent dome. The city’s people would obviously be unable to survive for long inside it unless they had access to air, water and other essential resources from outside. Think through how far the dome would have to extend in order to keep the city going indefinitely given a certain level of consumption, energy and resource supply and technological development and you are ecological footprinting. London was found to have a footprint of 49 million hectares, about the land area of Spain (!) in a study by Best Foot Forward in 2002. You could also picture a dome totally enclosing a person, a house, factories, offices, a country, group of countries – or indeed a planet! You could draw a boundary around various products, say beef or cars, and assess the ecological footprint of the product’s lifecycle.
An ecological footprint is the total land and sea area required to supply the resources and safely absorb the wastes and pollutants from a certain lifestyle and can be thought of at a range of levels. The unit of land area used is global hectares, where one global hectare is equal to one hectare (2.47 acres) of world average biological productivity with current technology. Some, like WWF, use ‘planets’ as a unit, which is good because any footprint greater than one immediately illustrates the unsustainability, excess demand or ecological debt (world footprint is now 1.3 planets and if current patterns are not changed we are heading for a 2 planet footprint by 2035). Land and sea is needed for: crop, animal and forest products; for housing and infrastructure; to absorb carbon emissions from fuel burning; biodiversity preservation; human wellbeing and quality of life.
William Rees came up with the ecological footprint idea, publishing the first academic paper on the subject*. Personal Environmental Impact Accounting, a concept closely related to ecological footprinting, was developed in the early 1990s by Don Lotter and released in 1992 as EnviroAccount software which became Earth Aware software in 1996 (still available as a free download from the internet). Rees worked on footprinting with Mathis Wackernagel in the early 1990’s at the University of British Columbia, Canada, the two publishing a book Our Ecological Footprint in 1996 explaining the concept. Much work has since followed eg the book Sharing Nature’s Interest published in 2000, written by Wackernagel, Nicky Chambers and Craig Simmons.
Footprinting’s methodology for the national level is detailed in the 2006 Living Planet Report and the Global Footprint Network's method paper. The Global Footprint Network has clearly indicated how research should be used to improve the method. This is important because different methods have been used in various studies with respect to: sea area; fossil fuels; imports and exports; and nuclear power. Data sources used have varied. Whether to use average global numbers or local numbers when looking at a specific area has been an issue. Including space for biodiversity has been debated. Footprint standards, are bringing methods closer together, making data more consistent and comparable. EU assessment of footprinting has been positive and ackonwledges the work being done to perfect methods.
When consideraring footprint data it is important to remember what they don’t tell us in addition to what they do. The footprint concept is itself inevitably a simplification of reality. The computer models used to calculate footprints are further inevitable simplifications. This is both a plus and a minus of course. Footprints do not deal with that which it is difficult or impossible to convert to a land area: pollutant toxicity; health impacts; the depletion of non-renewable resources (though it does account for the energy, land and resources needed to process them); socio-economic impacts; noise and visual impacts, for instance.
Keeping in mind its limitations, ecological footprinting is an excellent tool for awareness raising, getting a sense of the overall scale of unsustainability by comparing it with actual land area. The biological capacity of an area indicates resources that can indefinitely regenerate without depletion or degradation. Most industrialised countries have insufficient capacity to support their population eg Netherlands (average footprint 4.8 gha/person, land area 0.8gha/person in 1999) unless they have large land areas and low population densities eg Canada (footprint 2.7 gha/person, land area 8.8 gha/person, in 1999). The world as a whole went into ecological debt (where consumption exceeds regerative capacity) on 19 Dec 1987 and because of unsustainable living we enter into this debt earlier every year – in 2008 we went into debt on 23 Sept!
*Rees, William E.(October 1992). "Ecological footprints and appropriated carrying capacity: what urban economics leaves out". Environment and Urbanisation 4 (2): 121–130.