Ecological Footprint

The ecological footprint is a metaphor for ecological impact, regardless of where that impact occurs. The ecological footprint is also an ecological accounting tool, a measure of the environmental impact of consumption and subsequent waste discharge. Consumption items are divided into food, shelter, transportation, and consumer goods and services. The consumption impact is measured by converting impact variables into the single unit of land, measured in hectares or acres. This includes land appropriated by fossil energy use, the built environment, gardens, cropland, pasture, managed forest, and land of limited availability, including untouched forests and nonproductive areas, such as deserts and icecaps. The major strength of the ecological footprint as a way of measuring the sustainability of cities is that it enables a picture of the flow of materials into and out of the city.

Bill Rees and his students, particularly Mathis Wackernagel, developed the concept of ecological footprints (EFs) as a way of ascertaining sustainability at the University of British Columbia in Vancouver, Canada. Most analyses of sustainability, whether radical or mainstream, recognize that major concentrations of human consumption generate impacts far beyond a nation or city’s formal boundaries. Prior to the invention of the concept of EFs, very few policy, lobby group, or academic analyses successfully moved beyond highlighting these external impacts as issues that needed to be addressed. Ecological footprint analysis managed to put forward a way of both measuring and vividly demonstrating how ecological impacts extend far beyond the official area of cities or countries.

The EF approach is similar to the idea of “ghost acres” developed by the Swedish academic Georg Borgstrom in 1965. The focus of Borgstrom’s work was adequate nutrition for a growing population. The ghost acres were comprised of fish acreage and trade acreage. Jim MacNeill and colleagues extended the concept in the lead-up to the Earth Summit in Rio de Janeiro in 1992. The metaphor of ghost acres for food production was extended to include other consumption concerns, and repackaged as “shadow ecologies.” More recently, William Catton discussed the idea of “phantom land.”

This concept refers to how humans currently use the ecological productivity of ecosystems that no longer exist. For example, nature cannot replace fossil fuels such as coal and oil at the rate that humans are diminishing the stock of nonrenewable resources. The goal of ecological footprints is to document “overshoot,” which refers to the excess global demand over global supply, of nature’s resources for human use. Since the original EF methodology was developed, a number of different approaches have emerged. At the Footprints Forum in Siena, Italy, in June 2006, an international standard for footprinting was introduced to ensure consistency. This standard was divided into application standards and communication standards. Standard number 15 attempts to clarify the relationship between EFs and sustainability; that ecological footprinting is a necessary criterion for sustainability, but it is not an absolute indicator of sustainability.

This point is crucial because the EF is a tool that may be used to inform choices and policy development, but it is not a predictive tool, nor can it be a surrogate for environmental policy. Although the national scale is used as a benchmark in the 2006 Footprint Standards, the EF approach can be used at a variety of scales that have been labeled sub-national. These include cities, regions, states, counties, and organizations. In the case of a city, the approach can be used to calculate the equivalent amount of land consumed for a city to function. This equivalent amount of land is influenced by changes in both population and per capita material consumption.