On the demand side, the Ecological Footprint measures a population’s demand for plant-based food and fiber products, livestock and fish products, timber and other forest products. It also accounts for space occupied by urban infrastructure, as well as the surface of forested land needed to absorb all the carbon dioxide emissions generated by that population through burning fossil fuels. The Ecological Footprint can be calculated for a single individual, city, region, country, or the entire planet.
On the supply side, the biocapacity of a given geographical entity (country, province, city) represents the capacity of its biologically productive land and sea area to provide ecological resources and services, given current technology and management practices. Biocapacity include forest lands, grazing lands, cropland, fishing grounds, and built-up land.
The gap between Ecological Footprint and biocapacity is determined by several factors. Our personal Footprint is the product of how many resources one uses and how efficiently these resources are being produced. The biocapacity per person is determined by how many hectares of productive area are available, how productive each hectare is, and how many people (in a city, country, or the world) share this biocapacity.
When a country’s biocapacity is greater than its population’s Ecological Footprint, the country has an “ecological reserve.” Many countries are “in the red,” however, meaning that they use more natural resources (Ecological Footprint) than their ecosystems can regenerate (biocapacity). They are running an “ecological deficit.”
Countries can run ecological deficits by liquidating their own resources (e.g. overfishing); importing resources from other areas; and/or emitting more carbon dioxide into the atmosphere than their own ecosystems can absorb.
When the entire planet is running an ecological deficit, as it has been since the early 1970s according to Global Footprint Network data, it is called “overshoot” since there can be no net import of resources to the planet.
Overshoot occurs when humanity’s Ecological Footprint is larger than Earth’s biocapacity. According to the most recent data, humanity’s Ecological Footprint amounts to 1.75 Earth’s biocapacity, with carbon emissions making up 60% of the Ecological Footprint.
Earth Overshoot Day marks the date when humanity’s demand for ecological resources and services (Ecological Footprint) in a given year exceeds what Earth can regenerate in that year (biocapacity). In 2019, it landed on July 29.