What Is Ecological Footprint? Definition and How to Calculate It

Ecological footprint is a method of gauging humans’ dependence on natural resources by calculating how much of the environment is needed to sustain a particular lifestyle. In other words, it measures the demand versus the supply of nature.

The ecological footprint is one way of measuring sustainability, which refers to the ability of a population to support itself in the present without compromising that ability for the future. Environmental sustainability occurs when a population can support a particular lifestyle indefinitely while still meeting the demands placed on an environment. An example of environmental sustainability is producing an amount of pollution that the environment can handle.

Ecological Footprint Definition

More specifically, the ecological footprint measures the amount of “biologically productive” land or water that enables the population to sustain itself. This measurement takes into account the resources a population needs to (1) produce goods and (2) “assimilate,” or clean up, its waste. Biologically productive land and water can include arable land, pastures, and parts of the sea that contain marine life.

The units for ecological footprint are global hectares (gha), which measure the amount of biologically productive land with a productivity equal to the world average. This land area is measured in terms of hectares, which each represent 10,000 square meters (or 2.47 acres) of land.

For some perspective, some ecological footprints of several countries are listed below. These values were listed for the year 2017 in the Global Footprint Network's Open Data Platform:

• United States: 8.0 gha/person
• Russia: 5.5 gha/person
• Switzerland: 4.5 gha/person
• Japan: 4.7 gha/person
• France: 4.6 gha/person
• China: 3.7 gha/person
• Indonesia: 1.7 gha/person
• Peru: 2.1 gha/person

Note that ecological footprints can be counterbalanced by biocapacity, which refers to the ability of a biologically productive area to continuously generate renewable resources and clean up its wastes. An area is considered unsustainable if a land’s ecological footprint is greater than its biocapacity.

Britannica reports that the ecological footprint concept was developed by a Canadian ecologist named William Rees and was further developed in a dissertation by Swiss urban planner Mathis Wackernagel, under Rees' supervision. The pair published a book in 1996 called "Our Ecological Footprint" that expanded the concept for a lay audience.

Ecological Versus Carbon Footprint

Ecological footprints and carbon footprints are both ways of measuring something’s impact on the environment. However, a carbon footprint measures the total amount of greenhouse gas emissions caused by an individual, organization, or activity. A carbon footprint is measured in units of carbon dioxide equivalents, or CO2e, which quantifies how much a certain amount of a greenhouse gas would impact global warming in reference to carbon dioxide.

The carbon footprint thus concentrates on activities that would be related to greenhouse gas emissions, rather than considering an entire lifestyle as might be the case for calculating an ecological footprint. A carbon footprint would be used, for example, to determine the impact that burning fossil fuels or consuming electricity would have on the environment.

Ecological Footprint Calculation

The ecological footprint considers many variables, and the calculations can become complicated. To calculate the ecological footprint of a nation, you would use the equation found in this research paper by Tiezzi et al.:

EF = ΣT_i/Y_w x EQF_i,

where T_i is the annual amount of tons of each product i that are consumed in the nation, Y_w is the yearly world-average yield for producing each product i, and EQF_i is the equivalence factor for each product i.

This equation compares the amount of goods consumed in a nation relative to how many of those goods were produced in the world, on average. Equivalence factors, which differ depending on land use and year, help convert a specific land area into the appropriate number of global hectares. Yield factors take into account how different types of land can have smaller or larger impact on an ecological footprint calculation that factors in many types of products.

Example Calculation

The ecological footprint factors in the influence from many sources, but the calculation is very similar for each individual product. After finding out the ecological footprint for every product, you would add all your answers to figure out the overall ecological footprint.

Let's say you are growing carrots and corn on your farm and you want to figure out your farm's ecological footprint based solely on your crop production.

You know a few things:

• This year, you are harvesting 2 tons of corn and 3 tons of carrots from your farm.
• Your farm's average yield per hectare for carrots is 8 tons/ha for corn and 10 tons/ha for carrots.
• The yield factors for your corn and carrots are both 1.28 wha/ha. Here, wha stands for world-average hectare, which describes how much area of a specific type of land has a productivity equal to the world average.
  World-average hectares differ from global hectares in that global hectares do not discriminate by the type of land, and so allows for the direct comparison between vastly different products.
• The equivalence factor for your corn and carrots are both 2.52 gha/wha.

First, let's calculate the ecological footprint of your corn:

EF_corn = T_corn/Y_corn x YF_corn x EQF_corn

EF_corn = (2 tons) / (8 tons/ha) * (1.28 wha/ha) * (2.52 gha/wha) = 0.81 gha

Now, let's do the same for your carrots:

EF_carrots = (3 tons) / (10 tons/ha) * (1.28 wha/ha) * (2.52 gha/wha) = 0.97 gha

Therefore, the ecological footprint of growing your crops is:

0.81 gha + 0.97 gha = 1.78 gha

This means that in order to grow your crops, you would need 1.78 hectares of biologically productive land with a productivity equivalent to the world average. You can add in more terms to take into consideration other factors, like how much electricity you might need to run your farm.

To see if your farm is sustainable, you should check whether the ecological footprint you calculated is less than the biocapacity of the land you are growing your crops on. If so, your farm is producing crops at a rate that the land can handle.

Applying the Equation to Other Categories

The equation can also be applied to different individuals and situations. If you are growing crops and wanted to calculate your own ecological footprint, for example, you would take into account the annual yield of the product on your farm instead of the annual national yield, and calculate the yield factor for your particular location relative to the world. The product does not have to be a crop, either. The equation can be applied to other goods such as electricity.

Online Calculators

If you want to find out your own ecological footprint, some organizations have set up online calculators. You can check out Global Footprint Network, an organization aiming to create a sustainable future. It gives each person an estimate of their "personal overshoot day" and the results may surprise you.

This is a reference to Earth Overshoot Day, when the planet goes into resource overdraft to support lavish lifestyles, and when "humanity’s demand for ecological resources and services in a given year exceeds what Earth can regenerate in that year." Overshooting means that resources are being depleted at a rate that exceeds the capacity for regeneration.

Sources

• “Ecological Footprint.” The Sustainable Scale Project, Santa-Barbara Family Foundation, www.sustainablescale.org/conceptualframework/understandingscale/measuringscale/ecologicalfootprint.aspx.
• Galli, A., et al. “An Exploration of the Mathematics behind the Ecological Footprint.” International Journal of Ecodynamics, vol. 2, no. 4, 2007, pp. 250–257.
• “Handout: Ecological Footprints From Around the World: Where Do You Fit In?” Sierra Club BC, Sierra Club, 2006.
• “Open Data Platform.” Footprintnetwork.org, Global Footprint Network, data.footprintnetwork.org/#/.
• Srinivas, Hari. “What Is an Ecological Footprint?” Urban and Ecological Footprints, The Global Development Research Center, www.gdrc.org/uem/footprints/what-is-ef.html.