The Ecological Footprint (EF) is a resource accounting tool designed to quantify human demand on the planet’s ecosystems. It measures how much of the Earth’s regenerative capacity is being used by a population, individual, or activity. As a standardized metric, the EF translates complex resource consumption and waste generation into a single comparable unit, providing a clear picture of sustainability.
Defining the Global Hectare
The direct answer to the measurement unit of the Ecological Footprint is the global hectare (gha). A global hectare represents one hectare of biologically productive land or sea area with the world’s average productivity for a given year. This unit is necessary because not all land is equally productive; for example, a hectare of highly fertile cropland yields far more resources than a hectare of arid grazing land.
The gha allows for a standardized comparison across different land types and regions globally. To achieve this standardization, the actual physical area of a specific land type is multiplied by an “equivalence factor.” This factor adjusts the area based on its biological productivity relative to the world average. For instance, a physical hectare of rich cropland might equate to a larger number of global hectares than a physical hectare of less productive forest land. This step ensures that the final Ecological Footprint calculation is a meaningful and consistent measure of resource demand regardless of where the consumption occurs.
The Six Land Use Categories
The total Ecological Footprint is calculated by aggregating the demand placed on six distinct categories of biologically productive surface area, all measured in global hectares. This comprehensive approach accounts for the diverse ways humanity uses and impacts natural resources. The categories cover the resources consumed and the waste absorbed by human activity.
The six categories are:
- Cropland: Measures the area required to grow all plant-based products, including food, animal feed, and fiber crops. This land type is typically the most biologically productive and often has the highest equivalence factor.
- Grazing land: Accounts for the pasture and rangeland needed to support livestock that provides meat, dairy, and leather products.
- Forest land: Calculates the area required to supply timber, fuelwood, and other forest products. This category also includes the land necessary to absorb the majority of human-generated carbon dioxide emissions (often called the Carbon Footprint component).
- Fishing grounds: Measures the aquatic area required to support the annual harvest of wild-caught and farmed aquatic species.
- Built-up land: Accounts for the biologically productive area converted for human infrastructure, such as housing, roads, and industrial structures.
The cumulative demand across these six categories, converted into global hectares, results in the final Ecological Footprint score.
Comparing Demand to Earth’s Capacity
The Ecological Footprint (human demand) is analyzed in direct comparison to the Earth’s Biocapacity (the planet’s supply of regenerative resources). Biocapacity is also measured in global hectares, quantifying the ability of ecosystems to produce resources and absorb waste. This comparison is the central function of the accounting framework for determining humanity’s sustainability.
When a population’s Ecological Footprint exceeds the available Biocapacity of a region, the area is considered to be running an ecological deficit. This means the population is consuming resources faster than the local ecosystems can regenerate them. At the global level, when humanity’s total demand exceeds the Earth’s total Biocapacity, the world is in a state of overshoot.
Overshoot occurs when humanity meets excessive demand by liquidating natural capital, such as depleting fish stocks, deforesting land, and allowing carbon dioxide to accumulate in the atmosphere. The date each year when the global Ecological Footprint exceeds the planet’s Biocapacity is marked as Earth Overshoot Day. The global hectare provides the metric needed to track this imbalance and demonstrate that human consumption currently requires the natural resources of more than one planet.