September 28 is Earth Overshoot Day


What is Overshoot?

Just like any company, nature has a budget — it can only produce so many resources and absorb so much waste every year. The problem is, our demand for nature’s services is exceeding what it can provide.

In 2008, humanity used about 40% more in one year than nature can regenerate that same year. That means it takes over a year and three months for the Earth to regenerate what humanity is using in one year. This problem — using resources faster than they can regenerate and creating waste faster than it can be absorbed — is called ecological overshoot.

We currently maintain this overshoot by liquidating the planet’s natural resources. For example we can cut trees faster than they re-grow, and catch fish at a rate faster than they repopulate. While this can be done for a short while, overshoot ultimately leads to the depletion of resources on which our economy depends.

In fact, overshoot is at the root of the most pressing environmental problems we face today: climate change, declining biodiversity, shrinking forests, fisheries collapse and several of the factors contributing to soaring world food prices.

Why is Earth Overshoot Day Earlier Than Last Year

Earth Overshoot day (also known as Ecological Debt Day) was a concept devised by Global Footprint Network partner, nef (the new economics foundation). Each year, Global Footprint Network calculates humanity’s Ecological Footprint (it’s demand on cropland, pasture, forests and fisheries), and compares this with global biocapacity, the ability of these ecosystems to generate resources and absorb waste. Ecological Footprint accounting can be used to determine the exact date we, as a global community, begin living beyond the means of what the planet can regenerate in a calendar year.

Humanity first went into overshoot in 1986; before that time the global community consumed resources and produced carbon dioxide at a rate consistent with what the planet could produce and reabsorb. By 1996, however, humanity was using 15 percent more resources in a year than the planet could supply, with Earth Overshoot Day falling in November. This year, more than two decades since we first went into overshoot, because we are now demanding resources at a rate of 40 percent faster than the planet can produce them, Earth Overshoot Day has moved forward to September 23.

How is Earth Overshoot Day Calculated?

[ world biocapacity / world Ecological Footprint ] x 365 = Ecological Debt Day

Put simply, Earth Overshoot Day shows the day on which our total Ecological Footprint (measured in global hectares) is equal to the biocapacity (also measured in global hectares) that nature can regenerate in that year. For the rest of the year, we are accumulating debt by depleting our natural capital and letting waste accumulate.

The day of the year on which humanity enters into overshoot and begins adding to our ecological debt is calculated by calculating the ratio of global available biocapacity to global Ecological Footprint and multiplying by 365. From this, we find the number of days of demand that the biosphere could supply, and the number of days we operate in overshoot.

This ratio shows that in 2008, in just 267 days, we demanded the biosphere’s entire capacity for the year. The 267th day of the year is September 23.

If you have further questions about the Ecological Footprint and overshoot calculations, there are a number of resources available through our website to learn more: See the Living Planet Report and the Earth Overshoot Day Media Backgrounder for definitions, data and further information about overshoot. You can also read our methodology paper for a more technical overview of our calculation methods, and visit our glossary page for definitions of terms. If you have further inquiries about Earth Overshoot Day, please contact Nicole Freeling.

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