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What is an ecological footprint?

An ecological footprint is the area required to provide the goods and services consumed by individuals, communities or organisations. It can also be derived for products or for particular activities. Using an 'area equivalence' expressed as 'global hectares', the ecological footprint expresses how much of nature's renewable bioproductive capacity (or 'interest') we are currently appropriating. If more of nature's interest is consumed than is available (i.e. nature's 'capital' is being reduced), then it is possible to assume that the rate of consumption is not sustainable (Chambers et al., 2000).

A snapshot approach

An ecological footprint is a 'snapshot' methodology. It is based on a year-specific data set - 2001 for Stepping Forward. An ecological footprint tells us how much bioproductive area would be required to support current consumption, and does not attempt to predict future or measure past impacts. It is likely that, due to technological changes and variations in material flows through the economy (consumption of resources), the ecological footprint (and biocapacity) will change over time, hence the need to focus on one year.

Area types

For the purposes of calculating an ecological footprint, bioproductive land and sea is categorised into four basic types (see Figure 3):

Figure 3
Area and sea types used to calculate an ecological footprint

fig 3
  • Bioproductive land - land required to produce crops, grazing (pasture), timber (forest) etc. Use of these land types is usually calculated separately.
  • Bioproductive sea - sea area required to provide fish and seafood.
  • Energy land - 'new' forest required for the absorption of carbon emissions to stabilise CO2 levels in the atmosphere. Calculations take into account the absorptive capacity of the oceans and discount it (Loh, 2002).
  • Built land - such as buildings and roads. Once built on, land is no longer bioproductive in any year.

In addition, a fifth type - biodiversity - refers to the area of land and water that would need to be set-aside to preserve biodiversity. This area of land and water is allocated in proportion to the ecological footprint – for example, the larger the ecological footprint the larger the responsibility to maintain biodiversity. As biodiversity was not included in the headline National Footprint Accounts, it was not therefore presented in the main ecological footprint results. If biodiversity were included, a South West resident's ecological footprint would increase to 6.31 gha per person.

The following examples illustrate the relationship between the four main types of bioproductivity when an ecological footprint is calculated.

Example 1

A cooked meal of fish and rice would require bioproductive land for the rice, bioproductive sea for the fish, and forested 'energy' land to re-absorb the carbon emitted during processing and cooking.

Example 2

Driving a car requires built land for roads, parking and so on, as well as a large amount of forested 'energy' land to re-absorb the carbon emissions generated from petrol use. In addition, energy and materials are used for construction and maintenance of the vehicle.