Abstract
Ecological footprint measures how much of the biosphere’s annual regenerative capacity is required to renew the natural resources used by a defined population in a given year. Ecological footprint analysis (EFA) compares the footprint with biocapacity. When a population’s footprint is greater than biocapacity it is reported to be engaging in ecological overshoot. Recent estimates show that humanity’s footprint exceeds Earth’s biocapacity by 23%. Despite increasing popularity of EFA, definitional, theoretical, and methodological issues hinder more widespread scientific acceptance and use in policy settings. Of particular concern is how EFA is defined and what it actually measures, exclusion of open oceans and less productive lands from biocapacity accounts, failure to allocate space for other species, use of agricultural productivity potential as the basis for equivalence factors (EQF), how the global carbon budget is allocated, and failure to capture unsustainable use of aquatic or terrestrial ecosystems. This article clarifies the definition of EFA and proposes several methodological and theoretical refinements. Our new approach includes the entire surface of the Earth in biocapacity, allocates space for other species, changes the basis of EQF to net primary productivity (NPP), reallocates the carbon budget, and reports carbon sequestration biocapacity. We apply the new approach to footprint accounts for 138 countries and compare our results with output from the standard model. We find humanity’s global footprint and ecological overshoot to be substantially greater, and suggest the new approach is an important step toward making EFA a more accurate and meaningful sustainability assessment tool.
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Notes
Two clarifications are in order. First, the footprint does not provide a way to measure the environmental area impacted from pollution directly, so these should not be inferred from our definition. Secondly, the freshwater footprint does not account for human water consumption, it only accounts for our use of inland fisheries. The first version of footprint ever circulated in academic circles by Dr William Rees and Mathis Wackernagel at the University of British Columbia in the 1990s did attempt to account for fresh water appropriation, but the approach was deemed inadequate and abandoned.
See www.myfootprint.org.
For example Staples, an office supply company in North America, recently released its corporate sustainability assessment report, with an emphasis in the text on the “environmental” footprint. However, the report presented raw descriptive data and no footprint calculations were performed.
See http://www.footprintnetwork.org/gfn_sub.php?content=standards.
It is also worth noting that the FAO considers GAEZ data to be of uneven quality and reliability and though various modes have been pursued for ground-truthing and verifying GAEZ suitability analyses, there is an acknowledged need for further validation of results and underlying databases (FAOSTAT 2005).
See www.rprogress.org/newprojects/ecolFoot/methods/.
The EF-GAEZ model seems to show a net negative footprint for fisheries. This, given the model assumptions, appears to be an indication of an error in the model or in the data. It amounts to about 0.0056 gha per capita. This may not have been reported previously due to rounding or could, in fact, be a relatively minor flaw.
GDP is an indirect measure of the absolute magnitude of energy consumption in a nation while the share of energy in the overall footprint is a relative measure. We included GDP in lieu of a more direct measure of energy consumption due to multicolinearity concerns with energy share and also because GDP is highly correlated with the overall size of the consumption footprint.
The proof is relatively straight forward. For crop land, a nation’s footprint = [crop production (C) in tons per year/global crop yield factor (G) in tons per hectare per year] × the crop land EQF (Q). Biocapacity = maximum crop land area (Am) × national crop yield factor (N) × the crop land EQF (Q) (Wackernagel et al., 2005). We can factor Q out of both sides of the equation, leaving [C/G] on the footprint side and AmN on the biocapacity side. We can rewrite N as [Y/G] since N is simply the ratio of a nation’s crop land yield (Y) to the global crop yield factor (G). For the world as a whole, however, Y = G so this term is simply 1. This leaves C/G on the footprint side and Am on the biocapacity side. C/G cannot be greater than Am on a global basis because G is simply global production/global crop land area in production or C/Ap leaving Ap on the footprint side and Am on the biocapacity side, with Ap ≤ Am by definition.
Abbreviations
- EF:
-
Ecological footprint
- EFA:
-
Ecological footprint analysis
- EF-GAEZ:
-
Ecological footprint based on GAEZ suitability indices
- EF-NPP:
-
Ecological footprint approach that employs net primary productivity
- EQF:
-
Equivalence factor
- FAO:
-
United Nations Food and Agricultural Organization
- GAEZ:
-
Global agricultural ecological zone
- GDP:
-
Gross domestic product
- GFN:
-
Global Footprint Network
- GHA:
-
Global hectare
- Gt C:
-
Gigatons of carbon
- HA:
-
Hectare
- IPCC:
-
Intergovernmental Panel on Climate Change
- NPP:
-
Net primary productivity
- RP:
-
Redefining Progress
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Venetoulis, J., Talberth, J. Refining the ecological footprint. Environ Dev Sustain 10, 441–469 (2008). https://doi.org/10.1007/s10668-006-9074-z
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DOI: https://doi.org/10.1007/s10668-006-9074-z