1. Earth’s Ecological Limits

While economies, populations and resource demands grow, the size of Earth remains the same. Since the 1970s, when global ecological overshoot became a reality, we have been using more renewable natural resources than our planet can regenerate. This is akin to drawing down the biosphere’s principal rather than living off its annual interest. To support our demands on nature, we have been liquidating resource stocks and allowing carbon dioxide to accumulate in the atmosphere.

Ecological overshoot is only possible for a limited time before ecosystems begin to degrade and possibly collapse. Impacts of ecological overspending are apparent already in soil erosion, desertification, reduced cropland productivity, overgrazing, deforestation, rapid species extinction, fisheries collapse and increased carbon concentration in the atmosphere.

Natural capital constraints also pose a threat to economic performance and economic stability.

2. Terms Defined

  • The Ecological Footprint measures the amount of biologically productive land and sea area required to produce all the resources a population consumes and to absorb its waste. The Ecological Footprint takes every year’s technological advances into account.
  • Biocapacity is the biologically productive area that provides renewable biological capacity, i.e., the ability of an ecosystem to regenerate biological resources and absorb wastes generated by humans.
  • Ecological overshoot occurs when human demand exceeds the regenerative capacity of a natural ecosystem. Global overshoot occurs when humanity demands more than what the biosphere can renew. In other words, humanity’s Ecological Footprint exceeds what the planet can regenerate. The biosphere’s renewable capacity includes the replenishment of resources and the absorption of waste, such as carbon dioxide from fossil fuel.
  • Earth Overshoot Day marks the date when humanity’s demand for ecological resources (fish and forests for instance) and services in a given year exceeds what Earth can regenerate in that year. We maintain this deficit by liquidating stocks of resources and accumulating waste, primarily carbon dioxide in the atmosphere. Andrew Simms originally conceived the concept of Earth Overshoot Day while working at the UK think tank New Economics Foundation.
  • Global hectares are hectares of biologically productive land and sea area with world average bioproductivity. Both biocapacity and the Ecological Footprint are measured in global hectares. (A hectare contains 10,000 square meters and corresponds to about 2.47 acres.)

3. How Earth Overshoot Day Is Calculated

Every year Global Footprint Network calculates the number of days of that year that Earth’s biocapacity suffices to provide for humanity’s Ecological Footprint. The remainder of the year corresponds to global overshoot. Earth Overshoot Day is computed by dividing the planet’s biocapacity (the amount of ecological resources Earth is able to generate that year) by humanity’s Ecological Footprint (humanity’s demand for that year). This ratio is multiplied by 365 to get the date when Earth Overshoot Day is reached:

(Planet’s Biocapacity / Humanity’s Ecological Footprint) x 365 = Earth Overshoot Day

4. Overshoot Trends

The estimated level of resources and ecosystem services required to support human activities today is just over 1.6 Earths. Since 1961, the first year consistent United Nations statistics were available, humanity’s demand on resources has gone from being within the means of what nature could support to significantly over budget. Our planet went into global overshoot in the early 1970s.

On a positive note, the rate Earth Overshoot Day has moved up on the calendar has slowed to less than one day a year on average in the past five years, compared to an average of three days a year since overshoot began in the early 1970s.

5. The Carbon Footprint, Climate Change, and the Paris Agreement

A major component of the Ecological Footprint is the carbon Footprint, which represents the land area required to sequester carbon dioxide emissions from fossil fuel burning and cement production. (Carbon Footprints can also be expressed in tons per year. Tons per year then can be converted into area by dividing the weight by the sequestration rate of ecosystems.)

Today, the carbon Footprint makes up 60% of humanity’s total Ecological Footprint. It is also the fastest-growing part of the Ecological Footprint. One hundred years ago, the carbon Footprint was a very small fraction of the overall Ecological Footprint. Since 1970, our total carbon Footprint has more than doubled (in total global hectares).

Humanity’s carbon Footprint is the leading driver of climate change, which is the most pervasive result— together with biodiversity loss—of our ecological overspending. Because we are emitting carbon dioxide into the air at a rate much faster than it can be absorbed, it is building up in the atmosphere and ocean. Therefore, significantly reducing the carbon footprint is an essential step not only to end ecological overshoot and living within the means of our planet, but also to mitigate climate change.

Fortunately, the climate agreement that was adopted at the United Nations Conference of Parties (COP) 21 last December potentially laid down the path. It mandates maintaining global warming within 2 degrees Celsius over pre-Industrial Revolution levels. This shared goal will require nations to implement policies to completely phase out fossil fuels by 2050. Whether promises made are kept will obviously depend on political will.

6. Population and Consumption

Overshoot is driven by four key factors: 1) how much we consume, 2) how efficiently products are made, 3) how many of us there are, and 4) how much nature’s ecosystems are able to produce. Technology and more intensive inputs have helped expand biological productivity over the years, but that expansion has not come close to keeping pace with the rate at which population and resource demand have expanded.

Global Footprint Network’s data show that both world population and consumption are increasing. Higher per capita demand leaves a smaller pool of resources for everyone. Larger populations mean finite resources must be divided among more people. Whatever the factors — consumption or population — humanity is simply demanding more than Earth can provide. This overuse cannot be maintained for long.

If we continue on the course estimated by moderate United Nations projections for increasing population and consumption, Global Footprint Network data show that we would need the capacity of two Earths to keep up with our level of demand by 2030 . Whether such continued levels of overuse are physically possible is highly uncertain. Staying on this course would put the well-being of many of the planet’s residents increasingly at risk.

7. How Precise Are Footprint and Biocapacity Results?

The national Footprint and biocapacity calculations are based on United Nations data sets, and use about 15,000 data points per country and year, from 1961 to 2013. In addition, the calculations use some complementary data points from the most recent scientific literature. It is not possible to verify the precision and reliability of all of the  underlying data, which may vary from country to country.

Global Footprint Network not only updates its data on a regular basis, but also improves its methodology and incorporates better data where available. Global Footprint Network estimates that the absolute precision may be within 10 percent to 20 percent. However, the assessments of overall trends are more robust – this means the relative position of a country for one year compared to previous years within one edition is typically more robust. In this respect, the data shows unequivocally that humanity’s demand on nature is at an unsustainable level — one year is no longer enough to regenerate humanity’s annual demand on the planet, even using conservative data sets that underestimate the gap between how much humans use compared to what nature can renew.

8. Contact and Global Footprint Network Information

Global Footprint Network is a research organization that is changing how the world manages its natural resources and responds to climate change. Since 2003 we’ve engaged with more than 50 nations, 30 cities, and 70 global partners to deliver scientific insights that have driven high-impact policy and investment decisions. Together, we’re creating a future where all of us can thrive within our planet’s limits.

For media inquiries, please contact:

Laetitia Mailhes (English & French) – California, United States
Media & Outreach
Global Footprint Network
+1 (415) 794-2884 (PDT = GMT-7h)

Ronna Kelly (English) – California, United States
Communications Director
Global Footprint Network
+1 (510) 839-8879 x 302 (PDT = GMT-7h)
+1 (510) 834-2563 (mobile)