Redefining Progress - The Nature Of Economics

Ecological Footprint

See also

  • Ecological Footprint

Ecological Footprint Modeling

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Strengths, Limitations, and Model Variations

The footprint's greatest strength may be in its conceptual simplicity as an indicator of sustainability. It is very clear that, if a society's footprint (appropriated bioproductivity) is larger than its available bioproductivity, it will not be able to sustain itself in the long term unless it appropriates biocapacity from others. Thus, tracking footprints over time can provide a clear indictor of progress toward sustainability and a clear indicator of resource injustice. Indeed, national footprint comparisons clearly reveal the systematic appropriation of global carrying capacity from poor nations by affluent nations. The large ecological footprints of the affluent nations very significantly transcend their own boundaries. For example, according to Footprint 2.0, the ecological footprint of North America is 1.8 times larger than it available bio-capacity and that of Western Europe is 2.7 times larger than its bio-capacity. By comparison, Africa's footprint is only 27% of its biocapacity.
Footprints can be calculated for any size population allowing resource use comparisons to be made on any scale of interest. For example, footprints are calculated for:

These strengths explain the large and growing use of ecological footprints as an indicator of sustainability and resource justice.

Limitations

While acknowledging the strengths of ecological footprinting, its limitations and variations in assessment methodology argue for its careful use. While EFA does provide a clear, intuitive measure of one important aspect sustainability, by accounting for demands on Earth's biological capacity, it does not capture other environmental strains that also systematically undermine sustainability and carrying capacity. Thus the ecological footprint cannot be relied upon alone to confidently assure that sustainability requirements are met.

Consider the following examples:
  • Ecological footprints do not account for the systematic degradation of ecological productivity from overgrazing, soil erosion, and unsustainable land management practices. For example, the ecological footprint of crop production is assessed as the land area under production, whether or not the production method is sustainable. (With respect to the energy footprint this relates to energy crop production such as corn for ethanol.)
  • Footprinting ignores the effects of toxic pollution on organisms and processes that sustain Earth's life support systems. For example pollinator populations like bats and bees are disproportionately impaired by toxic pollution from pesticide applications, undermining biological productivity. The inability to capture problems of cumulative environmental contamination is particularly problematic from an energy perspective.
    • Consider as examples the impacts of air pollution emissions from fossil fuel combustion:
      • Coal combustion is the larges source of mercury contamination worldwide, which is undermining the reproductive health of wildlife populations and the neurological development of children globally.
      • Combustion of leaded gasoline in motor vehicles was the largest source of lead to the environment, and still is in some countries. Its effects are similar those of mercury.
      • Oxides of sulfur and nitrogen from fossil fuel combustion cause acid rain, which has destroyed large fractions of forests and aquatic ecosystems in many parts of the world (by more than 50% in parts of Eastern Europe, for example). While air pollution regulations have contained these effects to a significant degree in affluent countries the problem is growing rapidly in Asia.
      • Ozone (produced by chemical reactions of primary combustion emissions in the atmosphere) has had similarly devastating effects, stunting forests and significantly reducing crop production.
    • Consider also the effects of energy-related toxic spills and wastes.
      • The potential future impact of high level nuclear waste (spent fuel) on future generations is not accounted for.
      • Neither is the systematic contamination of soils and groundwater by leaking fuel tanks accounted for. (More than 50% of tanks storing gasoline at US gas stations were found to be leaking before the problem was discovered and mitigation begun.)
As explained by Venetoulis and Talberth, "while such declines may be reflected in lost biocapacity in the future, they are not reflected in negative ecological balances in the present." Thus, ironically, while ecological footprints are used as indicators of sustainability, they fail to capture the systematic erosion of earth's carrying capacity that is the basis of sustainability. (Best Foot Forward summarizes the main critiques of the ecological footprint and the responses of its defenders.)

Finally, experience has demonstrated that we cannot predict all important sustainability impacts of human resource use. Examples include the unanticipated destruction of earth's protective ozone layer by chlorofluorocarbons and other chemicals. Ozone loss well on its way to undermining life on earth before the problem was discovered and addressed. Another example is the unanticipated endocrine disrupting effects of many chemicals now in widespread commercial use that are impairing reproduction of wildlife populations. Emerging new technologies whose sustainability implications are largely unknown but potentially serious include widespread use of genetically engineered crops, new introductions of genetically engineered livestock and other organisms, and just emerging products of nanotechnology.

Thus we must anticipate ecological surprises by building in a large buffer to our assessments of sustainability requirements.
This approach also makes sense given that we cannot begin to anticipate the synergistic effect of combined stresses on ecosystems. For example, air pollution makes forests more susceptible to pests, global warming increases pest populations. So, while each effect individually might cause manageable perturbation. Together they may result in total ecosystem collapse.

A first step toward including a buffer in a sustainability indicator was made by Redefining Progress in their most recent footprint modeling. Footprint 2.0, discussed below sets aside 13.4% of biocapacity for other species before calculating biocapacity available to humans. While essential, note that this approach to buffering puts all other species in peril of our miscalculations.

These arguments demonstrate that:

Footprinting really gives a lower bound on the sustainability impacts of human resource use. Having an ecological footprint smaller than available bio-capacity is a necessary condition for sustainability, but it is not a sufficient condition. To be reasonably confident that sustainability requirements are met, other factors must be tracked and a large substantial buffer must be incorporated to account for environmental surprises. Given the large uncertainties and the large stakes, the author recommends aiming to include a 50% buffer.

Differences in footprint models

While the footprint concept is simple--an accounting of the magnitude of humans' demand on biocapacity (i.e. the life support system)--methods of accounting that demand differ and therefore assessments of impacts differ as well. This section describes the two main national accounting systems reported in the Footprint of Nations report and the Living Planet Reports produced by Redefining Progress (RP) and the Global Footprint Network (GFN). The primary differences stem from how the energy footprint is assessed, which in turn changes the assessment of available biocapacity. The differences in the results of the two models are significant. Therefore it is important, if footprint comparisons are to be made across geographic regions or over time, one must stick to a single model.

The RP and GFN model evolved from the same original model, which I call Footprint 1.0 here. The model used to generate GFN's Living Planet Reports is unchanged from Footprint 1.0 in its basic assumptions, though model parameters were updated over time as better scientific information became available (1). In contrast, RP significantly modified the model for its most recent report, the Footprint of Nations 2005. That revised model is referred to here are Footprint 2.0.

The major differences come specifically from how the fossil fuel footprint is handled and related assumptions on how biocapacity is handled. Both models calculate the fossil fuel footprint as the land area needed to absorb the carbon dioxide emitted from combustion (see Calculating Fossil Fuel Footprints). But they make different assumptions on where carbon absorption is occurring and therefore on the carbon uptake rate.
  • Footprint 1.0 takes the total fossil carbon emissions, subtracts out the amount absorbed by oceans, and then calculates how much regrowing forest ecosystem would be required to absorb the remaining carbon. Thus carbon uptake is assumed to occur at the rate at which a regrowing forests fix carbon.
  • Footprint 2.0 assumes that the entire global ecosystem (land and water) absorbs excess carbon at the current net uptake rate. This implies a far lower rate per hectare than assumed by Footprint 2.0, as indicated in the table below.

These assumptions force very different approaches to biocapacity estimates. Footprint 1.0 restricts biocapacity to selected ecologically productive lands and waters and allows land to serve only one resource provisioning or waste assimilation service at a time. In sharp contrast, Footprint 2.0 has the entire planet sequestering carbon, while at the same providing other services (crop, forest, and pastureland products, fish and built area). Details and justifications are provided in Venetoulis and Talberth. These differences and those discussed below are summarized in the Table 1.

Table 1. Different assumptions used in footprint models.

Table 1. Different assumptions used in footprint models.
Footprint 1.0 (Living Planet Report 2004) Footprint 2.0 (Footprint of Nations 2005)
Land and water can only serve one resource provisioning or waste assimilation service at a time. Land and water serves for resource provisioning and carbon sequestration at the same time.
Biocapacity area is restricted to selected ecologically productive lands and waters. Total biocapacity is equal to that total land plus water area, which is considerably smaller than earth's surface. Biocapacity includes all of earth's surface, land plus water. Because these are allowed to serve double duty for resource provisioning and carbon absorption the total biocapacity is considerably larger than the surface of the earth.
Carbon sequestration occurs at the rate of regrowing forests (0.95te-C/gha/yr). Carbon sequestration occurs at rate of global net primary productive (0.06te-C/gha/yr).
No biocapacity is reserved for other species. Sets aside 13.4% of biocapacity for other species.
Uses global agricultural ecological zone (GAEZ) suitability indices to determine the relative biological capacity of different areas. Uses net primary productivity (NPP) to determine the relative biological capacity of different areas.

The results of these different assumptions are large differences in footprint and biocapacity estimates, as shown in Table 2. Note that biocapacity and footprint areas are measured in different units from the actual land and water areas because these incorporate both the area of the indicated ecosystem and a measure of its relative productivity. To make that distinction clear, the units of biocapacities and footprints are called global hectares (gha) rather than hectares (ha).

global hectares = actual hectares x equivalence factor

The equivalence factors indicate how productive a given ecosystem is compared to global average productivity, but Footprint 1.0 and 2.0 use a different basis to determine the productivities of different regions. Footnote 1.0 bases productivity values on the Food and Agriculture Organization (FAO) Global Agricultural Ecological Zone (GAEZ) suitability indexes, effectively a measure of how good land is for agriculture. Footnote 2.0 uses the average net primary productivity of the land areas to determine their productivity. These differences are documented in Table 3.

Using 'global hectares' for bioproductivity and footprints, rather than actual land areas, allows one to make meaningful comparisons. For example, two nations with comparable land areas will have very different biological productivities, and hence very different abilities to provide a given population with ecological resources and services if one is located in semi-arid dessert and the other in tropical rainforest. Similarly more area will be required to provide ecological resources from a low productivity region than from a high productivity region.

Table 2. A comparison of actual land areas, biocapacities, and footprints for Footprint 1.0 and 2.0.

Table 2. A comparison of actual land areas, biocapacities, and footprints for Footprint 1.0 and 2.0.
Region Actual land areas
(B ha)		 Biocapacity
Footprint 2.0
(B gha)		 Biocapacity
Footprint 1.0
(B gha) 		Footprint
Footprint 2.0
(B gha)		 Footprint
Footprint 1.0
(B gha)
crop land 1.5 2.8 3.2 3.2 3.2
forest 3.6 10.9 5.1 2.9 1.2
pasture 3.0 7.4 1.6 2.9 0.6
built areas 0.2 0.1 0.6 0.3 0.6
less productive lands 6.6 4.8


energy land(*)
50.9
119.2 7.0
Total land 14.9 77.0 10.6 128.5 12.6
WATER AREAS




marine and inland fisheries 2.1 5.4 0.8 6.4 0.8
open ocean 34.4 14.4


Total water< 36.5 19.8 0.8 6.4 0.8<
TOTAL (land + water) 51.4 96.7 11.4 134.9 13.5


Table 3. Equivalence factors used in Footprint 1.0 and 2.0.

Equivalence factors indicate the productivity of an ecosystem relative to an average productivity.
Table 3. Equivalence factors used in Footprint 1.0 and 2.0.
Ecosystem Footprint 2.0 Equivalence Factors (based on NPP) Footprint 1.0 Equivalence Factor (based on GAEZ suitability indicators)
Crop land
 2.12
 2.11
Forest land
 3.29
 1.35
Pasture land
 2.42
 0.47
Built space
 0.5
 2.11
Less productive land
 1.04
 na
Marine and inland fisheries
 2.67
 0.35
Energy land
 na
 1.35
Open ocean
 0.47
 na

Questions

  1. What human activities are captured in ecological footprints?
  2. What units of measure are used to quantify ecological footprints?
  3. How do the ecological footprints of nations illustrate global environmental justice problems? (Use footprint estimates from the Living Planet Report 2006 to support your argument.)
  4. Calculate your own footprint using the Ecological Footprint Quiz. How does your own ecological footprint compare to the available per capita biocapacity on earth?
  5. What are the strengths and shortcomings of the footprint as an indicator of ecological sustainability?
  6. Name several kinds of environmental stresses that are not captured by the ecological footprint?
  7. How can the problem of ecological surprises be handled when assessing sustainability requirements? Give a concrete example.
  8. Explain the problem of synergisms and how they compound ecological uncertainties.
  9. Give some examples of how the ecological footprint is currently being used.
  10. What does the current size of human's global ecological footprint imply about the sustainability of current societal activities?
  11. If different footprint models give significantly different results does footprinting have any utility? Think of the big picture of the results. What do both sets of results tell us?
  12. Is a society that has a footprint smaller than its available biocapacity necessarily operating sustainably? Explain your answer.

Independent Study

To get an idea of what the ecological footprint ignores, research the impact of air pollutants from fossil fuel combustion on ecosystems and human health, worldwide or in your region. (Hint: What pollutants are emitted? Where do those pollutants end up in the environment? What are their impacts on biocapacity?)

Sources

Venetoulis, Jason and John Talberth, Redefining the Ecological Footprint (Submitted for publication). Download.

Notes

(1) We note that model parameters in Footprint 1.0 and 2.0 have diverged somewhat over time as well, though their effect is much smaller than the differences resulting from differences in carbon uptake assumptions. Footprint 1.0, used for the 2004 Footprint of Nations (FPN) report, assumed oceans absorb 35% of fossils fuel emissions. The most recent Living Planet Report model assumed 27%. Footprint 1.0 used a carbon sequestration rate of 0.95 te-C/ha/yr while FPN used 1.0te-C/ha/yr. While the latter may be due to rounding, the former, the former appears to result from the use of different sources and time periods. The 35% is consistent with the 1989 - 1998 reported in IPCC Special Report on Land Use, Land Use Change and Forestry, and reproduced in the Fossil Fuel Footprints page. The 27% figure is an average for the 1980 and 1990 taken from the Intergovernmental Panel on Climate Change in Chapter 3 of their synthesis report Climate Change 2001: The Scientific Basis. These differences are legitimate, reflecting uncertainties in underlying climate science. The same variation arises in the climate change modeling performed by different groups, and is reflected in the spread of predictions about the magnitude of warming to be expected from a doubling of the atmospheric carbon dioxide concentration.