Ecological Footprint (EF)

“ECOLOGICAL FOOTPRINT” (EF) refers to a system of measurement developed for estimating human appropriation of ecological resources relative to biologically productive (bioproductive) land area. EFs can show how much land is needed to sustainably support a human population, nation, or a specific component of society, such as a commodity (e.g., soybeans), transportation system (e.g., auto transit), or lifestyle (i.e., a consumption pattern). The utility of footprint analysis (FA) is best understood by considering the ecology of a modern city. Urban inhabitants are concentrated within city bounds but they rely on the importation of resources and exportation of wastes to survive.

Therefore, the land area necessary to produce resources and absorb wastes far exceeds the actual geographic boundaries of the city (or nation)—in wealthy nations ecological flows may be distributed across the planet. FA provides a framework for tracking these resource and waste flows and converting them into a common metric—land area (hectares) per capita—by making use of widely available economic statistics.

The calculation of an EF is based on two key assumptions. First, it is possible to reasonably track most human resource consumption and waste generation, and translate these flows into bioproductive land areas. Second, it is possible to standardize varying land areas by weighting each according to their “potential biomass productivity.” The latter refers to production potential that is of economic interest to society, not the diverse assemblage of other organisms necessary for human survival, or biodiversity. Biodiversity is included in national and global analyses but there is much debate over how much land must be set aside. (Estimates range from 8 to 75 percent; in practice, the conservative World Commission on Environment and Development [WCED] estimate of 12 percent of bioproductive land is simply added to the footprint total for the given social unit.) EFs omit resource uses for which conversions into bioproductive land are difficult, such as the impact of local fresh water use, as well as any impact that systematically reduces the ability of ecosystems to regenerate, such as the release of nonassimilable and/or bioaccumulating chemicals (e.g., uranium, polychlorinated biphenyls [PCBs], and mercury).