The Day the Earth Ran Out

The Causes and Consequences of Earth Overshoot Day

Officials from the China's Water Conservancy Bureau walk on the fringe of a desert.
Officials from the China's Water Conservancy Bureau walk on the fringe of a desert, which has been planted with grass to prevent desertification, December 8, 2010. (Courtesy Reuters)

Many readers will be familiar with the worrisome, white-knuckle wait that comes when you drain your checking account long before payday, the anxiety that builds until the coffers are replenished. That is what all of humanity has signed on for, effective today.

Earth Overshoot Day marks the moment when, according to Global Footprint Network, an independent think tank based in the United States, Switzerland, and Belgium, humanity’s demand for natural resources exceeds the earth’s ability to renew them in a year. As of today, just 34 weeks into 2013, we are officially in ecological overdraft.

Scientists and data-crunchers at Global Footprint Network calculate Earth Overshoot Day by dividing the earth’s current biocapacity (the area of land and water available to produce renewable resources and absorb CO2 emissions) by the world’s ecological footprint (the area of land and water required to meet humanity’s demand for resources and absorb waste). They then multiply the quotient by 365, the number of days in a calendar year. That number reveals Earth Overshoot Day. This year, that day arrived two days sooner than it did last year. It has come earlier, by about three days each year, since 2001. 

Both biocapacity and ecological footprint are measured in global hectares, a common unit that encompasses the average productivity of all the biologically productive land and sea area in the world in a given year. Measurements are drawn from Global Footprint Network’s National Footprint Accounts, datasets for more than 230 countries, territories, and regions that contain more than 6,000 annually gathered data points per country. Although not yet perfect, these accounts provide the most comprehensive available aggregate indicator of human pressure on ecosystems. 

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