A Bioproductive 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 Bioproductive 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.

For the purposes of calculating a Bioproductive Footprint, bioproductive land and sea is categorised into four basic types

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 Bioproductive Footprint - for example, the larger the Bioproductive Footprint the larger the responsibility to maintain biodiversity. As biodiversity is not included in the National Footprint Accounts, it is therefore not presented in the main Bioproductive Footprint results.

The capacity to produce biomass such as crops, grass or timber.

The total bioproductive area of a country or region.

TThe Bioproductive Footprint (as measured using global average yields) is normalised by applying equivalence factors. These are multipliers which adjust different area and sea types according to their relative bioproductivity.

When calculating the biocapacity of an area, the land types and sea available are normalised to world average equivalents using locally derived yield factors. These are multipliers which express the extent to which local bioproductivity is more or less than the world average for that land or sea type.

To enable comparisons between regions with different bioproductive capabilities, the Bioproductive Footprint is presented in global hectares (gha).

To convert different areas with different productivities into standardised global hectares, two conversion stages are required:

For each area type, the local area is converted to a 'global average' equivalent area using yield factors - so if one hectare of land is twice as productive as the global average, it becomes two 'global average hectares' of that area type. The National Footprint Accounts give 'yield factors' for each nation to enable this conversion. These results are presented in specific area types, for example 'global average arable area' or 'global average forest area'. However 'global average hectares' for different area types represent different amounts of bioproductivity.

'Global average' areas for each area type (arable, pasture, forest, built land) are converted into standardised units of area by applying equivalence factors. The equivalence factors, from the National Footprint Accounts, are subject to change due to both data availability and variability in the bioproductivity of the planet over time. This international, standardised unit of area is the global hectare (gha).