An ecological footprint is a measure of human activity's impact on the planet. It illustrates how much productive land and water is necessary to sustain a defined population. It is expressed in terms of a single number or factor, which is expressed as a single number reflecting the amount of productive land or water resource area worldwide required to meet the needs of humanity. It takes into consideration material used, waste released, energy used, and other factors that are used to provide goods and services. The total number is then compared with the total amount of land and area available in the world in order to calculate the humanity's ecological footprint. This measure gives policymakers insight about the demands placed on ecosystems and assists in decision-making for future development.

See also: carrying capacity, ecological economics, climate change, fossil fuel, population growth