A term coined by ecologist William Rees and Mathis Wackernage to describe the total ecological impact (the amount of land, food, water, and other resources needed) to sustain a person or organization. This is usually measured in acres or hectares of productive land. It is used to determine relative consumption and is frequently used as an education and resource management tool. When addressing large populations (such as countries), the total productive capacity of the Earth is sometimes used. For example, on average, the population of the USA consumes so many resources that were the rest of the world’s population to consume at the same level, several more Earths would be needed to meet the demand.
More information: www.myfootprint.org and en.wikipedia.org/wiki/Ecological_Footprint