A. Definition

Ecological Footprints (EFs) are an assessment of humanities dependence on natural resources. For a certain population or activity, EFs measure the amount of productive land and water required for the production of goods and the assimilation of waste required to support that population or activity.

In 1999 the world average EF was 2.3 global hectares (5.6 acres), 20% above the current global capacity (Redfining Progress, 2002). In other words, the lifestyle of the average global citizen is unsustainable. We are using natural resources faster than they can be regenerated.

B. Main Features

Ecological Footprints provide concise, credible, comprehensive, detailed and scalable data based on best available scientific data and technology. The size of an EF can change over time, depending on population, consumption levels, technology and resource use.

EFs are measured in global acres (or global hectares). One global acre (or hectare) represents one acre (or hectare) of biologically productive land or water. Dividing a region's EF by its population gives the global acres (or hectares) per capita.

Wackernagel et al (1997) defined biologically productive areas as (a) arable land; (b) pasture; (c) forest; (d) sea space (used by marine life); (e) built up land; and (f) fossil energy land (land reserved for carbon dioxide absorption). The current global biologically productive area is 10.8 billion hectares, of which, 21% is productive ocean and 79% is productive land. This represents less than one-quarter of the Earth's surface (Redefining Progress).

An individual's resource consumption is not restricted to local resources. Humans use resources from around the world. Consequently, local, regional and global productive areas utilised by a certain population or activity, have to be incorporated into the EF. The final EF can be compared to the existing biologically productive area to determine how sustainable the activity, lifestyle or population is.

Various uses, mostly mutually exclusive uses, compete for biologically productive land and water. This includes human; flora; fauna; and conservation uses. Flora, fauna and biological conservation are accounted for in EF calculations. However, the amount of productive land given to this group varies between calculations.

EF calculations use official statistics and peer reviewed literature to gather data. Five assumptions underpin any EF calculation (Redefining Progress):

• Most of the wastes generated and resources consumed can be tracked.
• Most of these resource and waste flows can be converted into the biologically productive area that is required to maintain these flows.
• These different areas can be expressed in the same unit (acres or hectares) once they are scaled proportionally to their biomass productivity. That is, each particular acre can be translated to an equivalent area of world-average land productivity.
• Since these areas have been standardised and stand for mutually exclusive uses, they can be added up to a total representing humanity's demand.
• This area for total human demand can be compared with nature's supply of ecological services, since it is also possible to assess the area on the planet that is biologically productive.

The Association of Charted Certified Accountants (ACCA) defined the basic steps in an EF calculation - (a) define the scope of the study (what environmental and natural resource aspects or components will be incorporated in the EF calculation), (b) collect and tabulate data for each component, (c) multiply data by its conversion factor (this creates EFs for each data component), (d) add each individual EFs to generate the total EF, (e) normalise the total EF to generate per unit values (eg per capita, per $1000, per tonne, etc), (f) create scenarios by modifying input and output values, and (g) use the result in decision making processes, education, etc.

The advantage of EF calculations is that it uses a single, easy to understand unit of measurement which is comparable between activities and populations. EFs reinforce concepts such as "earthshare" and linkages can be made between local and global consumption. However, EFs can oversimplify issues, data can be hard to source and not all impacts (eg toxic waste) are calculated.

C. Organizational Proponent

Mathis Wackernagel and William Rees defined the concept of EF.

D. Case Studies and Examples

1. Ecological Footprint of London City
A resource flow and ecological footprint analysis of Greater London, prepared by Best Foot Forward Ltd in 2002 found that London's EF was 42 times London's current capacity, or 293 times the size of London. This equated to 49 million global hectares, twice the size of the UK, and roughly the same size as Spain.

2. Ecological Footprint of Countries
Redefining Progress calculated the 1999 EFs for a variety of nations. They found that Belgium and Luxembourg had the biggest ecological deficit at 5.6 hectares per capita. The USA, Japan and Netherlands also had high ecological deficits of greater than 4 hectares per capita. New Zealand, Australia, Peru and Brazil were found to be living within their biological capacity.

3. Ecological Footprint of Car Travel
The EF for UK car travel per person per kilometre for 1 year was calculated to be 0.000043 ha/passenger-km. Car occupancy, vehicle km traveled, fuel consumption, manufacture and maintenance of the car, road space and car road share were considered in the calculation.

E. Target Sectors / Stakeholders

Consumers, industry, research institutions and government are the main stakeholders. Government is responsible for implementing legislation, plans and policies, as well as providing support to encourage EF studies and recommendations. Research institutions are required to develop better technology or methodologies to do more with less whilst protecting the environment. Research institutions and government are also responsible for education and promotion.

F. Scale of Operation

Ecological footprints can be created on any scale - an individual, a business, a city, a country, a specific activity (eg driving to work), or a group of activities.

G. Links

• Global Development Research Centre - Urban and Ecological Footprints
• Redefining Progress 2002 Ecological Footprint Accounts: Moving Sustainability From Concept To Measurable Goal
• City Limits London
• Association of Charted Certified Accountants (ACCA) Ecological Footprinting Analysis: Towards a Sustainability Indicator for Business