Earth Overshoot Day marks the date when humanity’s demand for ecological resources and services in a given year exceeds what Earth can regenerate in that year. We maintain this deficit by liquidating stocks of ecological resources and accumulating waste, primarily carbon dioxide in the atmosphere..Earth Overshoot Day marks the date when we (all of humanity) have used more from nature than our planet can renew in the entire year. We are using 1.7 Earths.
We use more ecological resources and services than nature can regenerate through overfishing, overharvesting forests, and emitting more carbon dioxide into the atmosphere than ecosystems can absorb.
A country’s overshoot day is the date on which Earth Overshoot Day would fall if all of humanity consumed like the people in this country. Countries’ overshoot dates are calculated with Global Footprint Network’s National Footprint Accounts.
The date of Earth Overshoot Day is calculated by comparing humanity’s total yearly consumption (Ecological Footprint) with Earth’s capacity to regenerate renewable natural resources in that year (biocapacity).
Global Ecological Footprint and biocapacity metrics, in turn, are calculated each year with National Footprint Accounts. Using UN statistics, these accounts incorporate the latest data and the most updated accounting methodology (the National Footprint Accounts 2018 Edition feature 2014 data.) To estimate this year’s Earth Overshoot Day, Ecological Footprint and biocapacity are “nowcasted” to the current year using the latest data from additional sources, such as the Global Carbon Project and others.
To maintain consistency with the latest reported data and science, the Ecological Footprint metrics for all past years since 1961 (the earliest year data is available) are recalculated every year, so each year’s metrics share a common data set and the exact same accounting method. The annual dates of Earth Overshoot Day are recalculated accordingly.
Consequently, it is inaccurate to simply look at media accounts from previous years to determine past Earth Overshoot Days. Indeed, a true apples-to-apples comparison of Earth Overshoot Days can only be made using the same edition of the National Footprint Accounts. For instance, it would make no sense to compare the date of Earth Overshoot Day 2007 as it was calculated that year—and reported by the media at the time—with the date of Earth Overshoot Day 2018, because improved historical data and new findings such as lower net carbon sequestration by forests have slightly shifted the results. Even a few percentage points change can shift the date of Earth Overshoot Day by a good number of days.