EM SC 240N
Energy and Sustainability in Contemporary Culture

Ecological Footprint


Learning Objectives Self-Check

Read through the following statements/questions. You should be able to answer all of these after reading through the content on this page. I suggest writing or typing out your answers, but if nothing else, say them out loud to yourself.

Speaking of costs and benefits, in simple terms, there are two fundamental quantities a business (or individual) needs to know to determine if they are making or losing money: how much money is going into the budget (revenue) and how much is going out (expenses). If revenue exceeds expenses, then the business makes money. If costs exceed expenses, the business loses money. A business cannot lose money forever. Eventually, it will not be able to sustain itself.

The same principle applies to most natural resources in two fundamental ways: 

  1. I think we can all agree that the earth has a limited ability to produce natural resources such as trees, fish, crops, meat, fresh water, and so forth. If we harvest resources faster than they are replenished, the populations will diminish. You've probably seen images of clear-cut forests, read about places that are running out of fresh water, and heard about crop shortages, as well as other symptoms of overuse of resources.
  2. The earth also has a limited capacity to absorb carbon dioxide and other wastes/emissions. We can see the immediate result of exceeding that limit because we know that the concentration of CO2 in the atmosphere is increasing. But the bottom line is that if we emit wastes faster than they can be reabsorbed, they will accumulate in the environment.

Lesson 3 provides a lot of examples of the symptoms of overuse of natural resources, but for now, I'd like you to reiterate these two following basic truths:

  1. When a resource has a limited capacity to be replenished, if it is harvested faster than it is replenished, it will diminish.
  2. When waste is emitted faster than it can be absorbed, it will accumulate in the environment.
Graph of Atmospheric Carbon Dioxide at Mauna Loa Observatory
Figure 2.3: The concentration of carbon dioxide in the atmosphere has been directly measured since 1958, increasing from just above 315 parts per million (ppm) in 1958 to over 419 ppm currently. At a fundamental level, this increase is due to more carbon being emitted into the atmosphere than pulled from it.
Click Here for Text Alternative for Carbon dioxide Chart

A chart showing global carbon dioxide increase since 1958. The line gradually increases from 315 parts per million (ppm) in 1958 to over 419 ppm in August of 2019. Seasonal fluctuations occur, but only a few ppm each year. The graph shows a steadily increasing rate from 1958 to 2021.

Just as a business that loses more money than it makes runs a deficit, when humans overuse the capacity of the earth to replenish resources, it could be said that these places are running an ecological deficit. It stands to reason that if we could figure out our planetary capacity to generate natural resources (aka our "budget" or "revenue" of natural resources) and compare it to how much of that capacity we use (aka our "costs"), we could determine if we are losing or gaining ecological capacity. Luckily for us, some people have been working on this for the last decade or so and have come up with the concept of ecological footprint.

Illustration showing that if you cut 3 out of 5 trees down and 1 grows back, you have 3 trees left, then if you cut 3 more down and 1 grows back, you have 1 left.
Figure 2.4: Overharvesting of natural resources. This is a simple example of how renewable but limited resources can be diminished. If you start with five trees and harvest three of them while one grows back, you are left with three trees. If you then harvest three more of them while one grows back, you are left with one tree. This is obviously not sustainable, regardless of the scale or resource, as long as that resource has a limited capacity to regenerate itself.
Image Credit: D. Kasper, tree images courtesy of GoodFreePhotos

To Watch Now

Watch this short (2:58 minute) video from Mathis Wackernagel, who originated the concept of ecological footprint. He is currently Executive Director of the Global Footprint Network, which specializes in calculating ecological footprints.

The Ecological Footprint: Accounting for a Small Planet
Click Here for Transcript of The Ecological Footprint Video

We have been the most successful species on this planet. Two hundred years ago, nobody could have imagined the kind of lives we are living today: the cities we have been able to construct, and the technologies we have been able to create. And so, we are asking ourselves, how will we be able to maintain success in the future? Since the end of World War Two, we have more than doubled our population, and we are consuming far more per capita. In the last century alone, we are now consuming tenfold the energy that we did hundreds of years ago, and we are recognizing that the planet is getting awfully small.

If we just compare, you know, how successful we have become as a species. We as a species, together with our cows and pigs, are about 97 percent of the biomass of all vertebrate species. But only about three percent are wild species, so we have been able to dominate the whole ecosystem of the planet. Now that may be a success, but its success also had its cost: that the planet is getting awfully small. That’s why we have developed the ecological footprint to start to measure how big are we compared to the biosphere; how can we actually use our ecological assets more effectively to live well on this planet? Now the ecological footprint is a very simple tool. It's a tool like a bank statement that tells us on the one hand how many resources do we have that renew itself, thanks to the biosphere that is powered by the sun, and how many do we use, and then you can see to what extent we are actually dipping into the overall capital or to what extent we're really living within that interest that nature provides us.

If you want a real simple and effective model of how the economy operates, just take the cow. Because everything that enters the cow as food will leave again. Very similar to an economy, a cow also produces a value-added, the milk. The milk, too, whether you consume it or not, becomes waste.

So, a farmer knows how much area, how much pasture, how much cropland, and how big of a farm is necessary to maintain his or her cow herd. Now the same way we can see how much area is necessary to support me or to support our cities, to support our economies, to support the world as a whole, all humanity - to maintain all the resources we consume and to absorb the waste - that's what the ecological footprint measures for you.

Credit: Bullfrog Films

Suggested Reading

For some deeper insight into ecological footprint, read Chapter 4 of Is Sustainability Still Possible?: "Getting to One-Planet Living," by Jennie Moore and William E. Rees. (See the Modules tab for a digital copy.)

"Ecological Footprints estimate the productive ecosystem area required, on a continuous basis, by any specified population to produce the renewable resources it consumes and to assimilate its (mostly carbon) wastes."
~Jennie Moore and William Rees, "Getting to One-Planet Living", p. 40

Dr. Wackernagel sums up the goal of ecological footprint analysis by asking a simple question: "How will we be able to maintain the success (of our society) in the future?" The ecological footprint is based on the recognition that humans depend on the earth's natural resources for survival, and that our "success" is predicated on the ability of the earth to replenish natural resources through time. In the simplest terms, the question we need to answer is:

  • "How many resources do we have that renew itself...and how many do we use?" as Dr. Wackernegel mentions.

We only have one earth, and this one earth can only regenerate so many resources in a given year (produce food, filter water, pull carbon dioxide out of the atmosphere, etc.) - this is our stock of resources. How can we use this information to determine whether or not we are overusing natural resources? In principle, it's relatively simple: If we compare the number of resources that are provided each year by the earth (one "earth") to the amount we use (our global ecological footprint), we can determine whether or not we are living within our ecological budget.

There are many implications of this, but there are two fundamental ones:

  1. If our global ecological footprint is one earth or less, we are living sustainably from the perspective of ecological footprint (note that this says nothing about the quality of life of people on the planet or the survival of specific species).
  2. If the global ecological footprint is greater than one earth, then the stock of biocapacity will diminish over time.

If biocapacity diminishes, eventually ecosystem collapse will occur, and ultimately societal collapse as well. This is what scientists refer to as a "very bad thing."

The bad news is that according to the Global Footprint Network, humans have been living beyond their ecological means for about 40 years now, as the chart below shows. The good news is, uh <checking notes>, well unfortunately in terms of global ecological footprint, there is very little good news. Just about every country across the world has an increasing ecological footprint.

A chart showing the ecological footprint vs. ecological capacity of the earth, through time.  We are now about 50% above ecological capacity. See link in caption for details.
Figure 2.5: Global ecological footprint through time. According to the Global Footprint Network, humans began to use more than one earth's worth of resources in the 1970s. The horizontal black line indicates an ecological footprint of 1. Under current conditions, we would need about 1.5 earths to sustain ourselves indefinitely. Note that this image indicates the contribution of various sectors to ecological footprint with color-coding.
Click here for a text description
According to the Global Footprint Network, humans began to use more than one earth's worth of resources in the 1970s. Under current conditions, we would need about 1.5 Earths to sustain ourselves indefinitely. Note that this image indicates the contribution of various sectors to ecological footprint with color-coding. The following components and approximate percentages correspond to the 2010 ecological footprint: Carbon: 53% Fishing grounds: 3% Cropland: 22% Built-Up Land: 4% Forest Products: 10% Grazing Products: 8%
Image Credit: Living Planet Report 2014, World Wildlife Fund

The Global Footprint Network (GFN) created another way to illustrate the same phenomenon by publishing the annual "Earth Overshoot Day." Earth Overshoot Day indicates the date in a given year after which humanity starts using more than a sustainable level of natural resources. As the GFN puts it: Earth Overshoot Day is when "we began to use more from nature than our planet can renew in the whole year." So, an earlier Earth Overshoot Day means that we are using up our resources faster. In 2016, this happened on August 8th. Pretty sad, right? Well, unfortunately in 2017, this occurred on August 2nd, and in 2019 it was July 29th! This is not the kind of downward trend sustainability-types like yourselves want to see. For the first time since they've been keeping track, Overshoot Day moved back about four weeks (to August 22nd) in 2020, but it was at the cost of millions of deaths and countless lives ruined. And of course, it was back to July 19th in 2021.

Sustainable Yield Natural Resource Management

While humans are unfortunately overusing resources on a global scale, it is not all bad news. If the natural replenishment rate of a renewable resource is known, then it is possible to harvest them at a sustainable rate. How can this be done? I want you to think about this for a minute before moving on. (Maybe take a look at Figure 2.4 for some inspiration.) 

Okay, here's the oh-so-elusive secret: If you want to maintain a supply of renewable natural resources, don't harvest them any faster than they can be naturally replenished. This practice is generally referred to as the principle of sustainable yield (you might also see it referred to as "maximum sustainable yield" or "sustained yield"). This is a pretty self-descriptive term, but Encyclopaedia Britannica provides a concise definition:

Sustainable yield "can in principle be maintained indefinitely because it can be supported by the regenerative capacities of the underlying natural system."

This can in theory be done for any renewable natural resource in order to maintain a steady supply over time. This is most often thought of in forest management and fisheries management but can be applied to any resource (e.g., soil, water, animal populations, plant populations). There are numerous examples of this in practice. For example, most of Sweden's forests are harvested using sustainable yield practices, and in fact, the total amount of forest has been increasing since at least the 1950s. Some forest areas under U.S. federal jurisdiction are required to be managed using sustainable yield practices, and the Maine lobster industry has been maintained for well over 100 years because of sustainable yield practices.

Please also keep in mind that - as indicated above - the same principle applies to emissions/pollution. If pollution is emitted faster than it can be safely absorbed, it will build up in the environment and/or cause damage to the environment. Rising CO2 levels are one example of this.

Unsustainable vs sustainable forest management. See link in caption for details.
Figure 2.6: Sustained yield forestry. If the rate of regeneration is known, and resources are harvested no faster than that, the resource can be sustained over time. Click for a text description.

Unsustainable Forest Management: Illustration showing that if you cut 3 out of 5 trees down and 1 grows back, you have 3 trees left, then if you cut 3 more down and 1 grows back, you have 1 left.

Sustained Yield Forest Management: Illustration showing that if you cut down 1 of 5 trees and 1 grows back, you have 5 trees left. Then, if you cut down one more and 1 grows back, you still have 5 trees left.

Image Credit: D. Kasper, tree images courtesy of GoodFreePhotos

It is very important to note a few caveats regarding sustained/sustainable yield management:

  • It can be very difficult to determine exactly how much of a resource is regenerated in a given time period. It is particularly difficult for large, dispersed resources such as fish and wild animals.
  • Even if the rate of replenishment is known, it can be very difficult to make sure everyone respects that limit. Again, open ocean fishing is a good example of this because there are thousands of fishing boats spread across the world, and not one single entity oversees them.
  • Even if a given resource is harvested at a sustainable rate, there may be other problems associated with that harvest. For example, industrial fishing operations - whether or not they take out too many fish - often cause incredible damage to wildlife and the ocean bottom. Here is a paper that describes some of these issues in fisheries management.

Overshoot and Collapse

How much longer can we continue to live beyond our ecological means? Unfortunately, there is no way to know. As Moore and Rees put it in the optional reading: "System collapse is a complicated process...We may actually pass through a tipping point unaware because nothing much happens at first" (p. 41). There is a phenomenon, most often used in biology/ecology, called overshoot and collapse that can help us understand some of the risks involved with overusing renewable resources and passing through such "tipping points."

To Read Now

This short article describes the well-documented example of overshoot and collapse on St. Matthew Island in Alaska. The rest of the article describes how this may be an analogy for humans, specifically with regard to energy. It is good food for thought.

  • St. Matthew Island - Overshoot & Collapse, Ned Rozell, and Dan Chay, writing for resilience.org. (By the way, resilience.org is a great website for sustainability-focused articles in a variety of fields.)

Overshoot and collapse can occur when there is insufficient immediate or short-term feedback to prevent an organism from acting against its own self-interest. If widespread human suffering occurred because of ecological overuse and it could be proven that resource overuse was the cause, it is likely that we would try to do something about it.

Of course, suffering is happening now, some of which is due to resource scarcity, but apparently not enough for us to address it. Regardless, it is possible to use more than our allotted biocapacity and survive, at least for a while. What's scary is that no one knows exactly how long we can keep using resources at this rate without reaching a tipping point. It may be 10 years, maybe 20 years, maybe even 50 years (very unlikely). It depends on a lot of factors, but one of the main problems is that by the time we realize collapse is occurring, it may already be too late to do anything about it. That is the "collapse" part of "overshoot and collapse." On St. Matthew Island, by the time the deer started running out of lichen to eat, it was too late. Humans are of course much more resourceful than reindeer (one would hope so, anyway), but there are likely tipping points that are points of no return. Chief among these are climate change and biodiversity loss, which will both be addressed in future lessons.

Check Your Understanding - Ecological Footprint

If the people in a country have a bigger ecological footprint than the physical size of the country, how can they continue to survive? For example, according to Global Footprint Network data (from overshootday.org):

  • The people of the U.S. collectively need an area more than twice the area of the U.S. to sustain themselves.
  • South Koreans would need more than eight (8!) South Koreas to sustain themselves!
  • And the population of the world as a whole would need 1.6 earths to sustain itself.

How is this possible? In other words, how can a country or the whole world use more resources than can sustainably be provided, and still survive?

Optional (But Strongly Suggested)

Now that you have completed the content, I suggest going through the Learning Objectives Self-Check list at the top of the page.