May 4th, 2022 – The day we consumed beyond our means for this year
Which key figures are used for the calculation?
Two key figures are required to calculate the overshoot days: the ecological footprint and the biocapacity of a country in gha (global hectares). The gha corresponds to one hectare with world average biological productivity.
Why these metrics and where do they come from?
The concept was developed in 1994 by Mathis Wackernagel and William Rees. The Global Footprint Network was founded by Wackernagel in 2003. supported by Nobel laureate Wangari Maathai, founder of the Worldwatch Institute Lester R. Brown and Ernst Ulrich von Weizsäcker.
The ecological footprint refers to the biologically productive area on earth that is necessary to permanently enable a person's lifestyle and standard (under today's production conditions). It includes land needed to produce clothing and food or to provide energy, but also for disposal of waste or to bind the carbon dioxide released by human activities.
Biocapacity is the available biologically productive area.
The Global Footprint Network obtains these two metrics from National Footprint and Biocapacity Accounts (NFAs). They have the data from 1961, but only up to 2018 due to the UN reporting process. This creates a delay of three to four years between the last data year (2018) and the presence.
How is the number of earths required and the specific overshoot day of a country calculated?
Let's take Germany as an example.
Germany's ecological footprint is 4.7 gha per person (as of 2018).
The global biocapacity is 1.6 gha per person (as of 2018).
Therefore, it would take (4.7 / 1.6) = 2.94 earths if everyone lived like the German population.
The exceeding day of Germany is calculated as follows:
365 x (1.6 / 4.7) = 124.25 rounded up to 125
The 125th day of the year 2022 is May 4th.
Do all countries have an overshoot day?