Is the Ecological Footprint policy-relevant in the UK?

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In 2007, the UK Department for Environment, Food and Rural Affairs (Defra) commissioned a study by independent consultancy Risk & Policy Analysis Ltd. to assess developments since 2004 in Ecological Footprinting methodologies and their practical application. The goal of the study was to evaluate the usefulness of the Ecological Footprint for policy-making in the UK . The final report , A review of recent developments in, and the practical use of, ecological footprinting methodologies, was released in late 2007. Click here to read the Global Footprint Network review of the 2007 Defra-commissioned report on the value of the Ecological Footprint methodology for UK policy use.

Is the Ecological Footprint misleading?

Global Footprint Network response to
“L’empreinte écologique: un indicateur ambigu”
by Frédéric Paul Piguet, Isabelle Blanc, Tourane Corbière-Nicollier, and Suren Erkman from the University of Lausanne and École des Mines
in Futuribles, October 2007


None should be asked to “believe in the Ecological Footprint” as an article of faith. Rather, as a scientific tool, Ecological Footprint accounts address, through empirical analysis and with ever increasing accuracy, one particular research question: how much of the planet’s productive capacity is demanded to support human activities? We believe that this is perhaps the single most important research question for the twenty-first century, one that humanity cannot afford to ignore. Failing to live within the budget of nature will eventually lead to ecological bankruptcy and collapse. There may thus be no single research endeavor more important than improving our knowledge of humanity’s demand on the biosphere through an open, transparent, scientific process. 

Frédéric Paul Piguet and his colleagues claim in their Futuribles article that the Ecological Footprint provides a poor and even misleading answer to this research question of how much of the planet we are using. This is a serious charge, and one that should not be taken lightly.  

Criticism is welcome

As stewards of the most widely used Ecological Footprints accounts and methodology in use today, we are the first to acknowledge that Footprint accounts can be improved. This is not unique to the Ecological Footprint, but a fundamental characteristic of all true scientific endeavors. As scientists, we are always eager to hear suggestions from others about how our methods can improve and what is not working.  

Many of Piguet et al.’s critiques, however, are based on misunderstandings of Ecological Footprint accounting methodology. Several also reconsider issues that have already been discussed at length by the Footprint community, though perhaps not as thoroughly in the French language. We regret that Piguet et al. chose to release their article without peer-review from other academics in the Footprint community. As a result, their article contains many misconceptions that we hope to clarify. 

Our response is divided into two parts. The first part explains what the Ecological Footprint actually attempts to measure and provides general background on our research process at Global Footprint Network. The second part responds to some of the main criticisms and misconceptions in Piguet et al.’s piece. A detailed, point-by-point response is downloadable here. Our first response was published in La Revue Durable (  

What is the Ecological Footprint, and how is it being improved?

Sustainable development implies a commitment giving all people the opportunity to lead fulfilling lives within the means of our one planet Earth. This concept continues to receive a great deal of attention in the public and political arenas. Yet when it comes to actual environmental strategies and policies, are our policy makers asking the right questions to lead us towards this goal? 

We know that when we catch more fish than can regenerate, fisheries eventually collapse; when we harvest more timber than forests can regrow, we advance deforestation; when we pump more water out of the ground than gets recharged, water tables drop; when we emit more CO2 than the biosphere can absorb, CO2 accumulates in the atmosphere and contributes to global warming. This overuse of resources is called ecological overshoot. Global ecological overshoot can be thought of as humanity withdrawing more from Earth’s biological bank account than is being deposited, which, as in the financial analogy, eventually leads to bankruptcy. To achieve sustainable development, it is critical to have information about both humanity’s demand on our planet and what our planet is actually able to provide. 

This is the research question answered by Ecological Footprint accounting. Footprint accounts measure the actual amount of biological resources produced and wastes absorbed by the planet in a given year, and compares this with how many resources humans extract and how much waste we generate. Our most recent accounts – the 2006 edition - show that, as of 2003, humanity was in overshoot, demanding more than 25% more than what the planet provided in that year.  

This graph and its supporting accounts provide a clear answer to the question of whether we are currently achieving sustainable development. The answer is a clear no – currently, global society is not living within the means of our planet, putting our society at economy at ever increasing risk. 

We encourage interested readers to learn more about our Ecological Footprint data and results by reading WWF’s Living Planet Report 2006, available for download – in 11 languages - at WWF or directly from us. Our calculation methodology is described in several academic papers, including Kitzes et al. (2007) or Kitzes et al. (2004). Also our data and methods page.

As with all rigorous scientific processes, our process of calculating Ecological Footprint accounts does not apply a single, fixed methodology, but rather continuously changes in response to new scientific information. We have several processes underway at Global Footprint Network to ensure that our calculations remain up to date and transparent for users. 

First, we engage in ongoing internal and community reviews of our methodology through the activities of our National Accounts Committee. This committee, composed of representatives from Global Footprint Network partner organizations, is responsible for suggesting methodological changes to our core National Footprint Accounts and considering any changes suggested from external academics and reviewers. All changes to our calculation methodology are open for public comment before implementation, in accordance with the Committee’s charter, and external parties are encouraged to submit recommended changes to the accounts directly to Global Footprint Network for consideration by the Committee. 

Second, we also engage in collaborative research projects with national governments and external consultancies to review our accounting methodology for specific nations. The governments of Switzerland (, Japan, and the United Arab Emirates have all engaged with us to review the methodology and data for their nations, and we expect soon to begin similar reviews with Belgium, France, Ecuador, and other nations. The results of these reviews are published publicly and have been used in the past to improve the quality of our Ecological Footprint accounts for all nations. 

With this background in our Footprint accounts and our methodological review process, let us now turn to a selection of the criticisms presented by Piguet et al.   

Are Ecological Footprint results insufficiently accurate for tracking overshoot?

As described above, current Ecological Footprint accounts show the existence of global overshoot, a fact also recognized by Piguet et al. Piguet et al.’s main criticism in fact is that global overshoot is significantly larger than what we calculate, concluding that our results lack sufficient accuracy for policy recommendations. 

We agree with Piguet et al. in recognizing that the current calculations can and are being improved, and that our results today represent only the best available data today. We strongly disagree, however, that our current state of knowledge is insufficient for taking policy action. Whether global overshoot is 25% or perhaps larger, the fact remains that global overshoot exists, that it continues to increase, and that globally the majority of consumption is taking place in North America, Western Europe, and eastern Asia. We believe that this recognition alone provides sufficient direction for a great deal of policy action. 

We also disagree with the Piguet et al.’s fundamental argument that the accounts’ carbon sequestration factor has very high uncertainty. Piguet et al. recalculates the National Footprint Accounts’ carbon Footprint using different sequestration rates, including cultivated forest sequestration rates (higher than ours) as well as a rate based on the global forests surface area and the effective carbon sequestered by terrestrial land area (lower than ours). They claim that the wide variation that these re-estimates produce in global overshoot means that current Footprint accounts are insufficiently precise for decision making. 

While at first glance, this exercise appears to be a valid form of sensitivity analysis, we believe that the high and low values chosen by Piguet et al. reflect a fundamental misunderstanding of the accounting framework, and are not valid for criticizing the precision of the existing carbon sequestration factor. To begin, the high sequestration rate based on cultivated forest is inconsistent with the underlying research question, which calculates Ecological Footprint and biocapacity in any given year based on the planet’s actual resource production and waste absorption in that year. Using a cultivated forest rate, and applying it to all forest area as potential sequestration, would be equivalent to saying that because aquaculture ponds placed in deserts could potentially provide more edible fish than we are currently catching, there is no overshoot in fisheries today. This is clearly a fallacious argument that confuses what is actually occurring today, which is what Ecological Footprint accounts measure, with what may or may not be true at some point in the future. 

On the other hand, the low sequestration value, based on the actual effective carbon sequestered by terrestrial land area, is similarly misguided. The current understanding is that the actual capacity or utility of each land type should be calculated based on its current use. For example, although many areas of the world could potentially grow potatoes, at varying yields (tones per hectare), we calculate the Footprint of a potato using the yield values for only that land which currently grows potatoes. 

Let us take an example of a 10 hectare potato field, producing 150 tonnes of potatoes, adjacent to a 10 hectare tract of forest that produces a single wild potato but could potentially be planted all to potatoes if cleared. In calculating the Footprint of a potato eaten by a consumer, we use a yield of 15 tonnes per hectare, based on the amount of potato produced per hectare of cropland. Even though there is a single wild potato produced in the forest area, we do not calculate the yield of potatoes as 7.5 tonne per hectare (150 tonnes divided by 10 hectares of potato field plus 10 hectares of forest), as the forest is not managed for producing potatoes. Even making allowances for multiple use, in which the 10 hectares of forest would be divided conceptually into two portions, perhaps 9.9 hectares devoted to timber and 0.1 hectare devoted to potatoes, the yield for potatoes in our example will still predominantly reflect the yield of the area devoted to potato production. Dividing total actual potato production by the sum of the areas of actual and potential potato field gives a nonsensical value for yield that is strongly biased downward. 

This is analogous to the error made by Piguet et al. in choosing to divide total carbon sequestration by all forest area, even that forest which is not devoted to or managed for carbon sequestration. Taking this approach gives a meaningless value for carbon sequestration. The most accurate method for approaching a carbon sequestration factor would be to calculate the actual carbon sequestration rate in a given year (not the potential, as suggested by Piguet et al.’s high estimate) on land that is actually devoted to carbon sequestration (not all land potentially available, as suggested by Piguet et al.’s low estimate). Thus we would ideally like to estimate the actual carbon sequestered by all land which is currently actively managed for carbon sequestration. As currently no global sequestration estimate exists just for the land set aside for carbon sequestration, the accounts use the actual average of all forest sequestration, managed and unmanaged, as a proxy for this, recognizing that the areas actually set aside for the purpose of carbon sequestration today are likely to be forests and that current data sets do not divulge whether these areas would be growing at natural rates or managed in some way. 

This calculation of the actual carbon sequestration rate on land set aside currently for the purposes of carbon sequestration would be an excellent research question, as suggested by Piguet et al. The current answers they provide, however, do not address this specific question and hence are clearly not applicable in a Footprint accounting framework as currently practiced. 

In addition to this point, we have noted several other common misunderstandings through the Piguet et al. paper. A short table provides a selection of the most important, several of which are also related to the carbon Footprint calculation methodology. A full list of 53 comments is available here.   


We welcome Piguet et al.’s contribution to the debate surrounding national Ecological Footprint accounting. In spite of the misunderstandings that we have clarified here, the article raises many important issues, and we look forward to continued dialogue with the authors and others in the community about how to continue strengthening and improving our ecological accounting systems to support a sustainable future.

© 2003-2007 Global Footprint Network
Last Updated: 05/09/2008

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