How do we measure sustainability? If not the ecological footprint, then what?

For years I have thought that the ecological footprint was a simple, powerful and accurate measure of sustainability. However a recent discussion has dethroned this concept in my mind. The idea of an ecological footprint makes intuitive sense. It measures the amount of land necessary to support one’s consumption habits. More intense consumers, with super-sized homes, gas guzzling SUVs, and larger lawns, have a larger ecological footprint because they consume more of our Earth’s resources.

The power of the ecological footprint is that it reduces consumption down to one measurable unit, land area, that is physically constrained by the size of our planet. Therefore accepting the ecological footprint also means accepting physical constraints to growth. Accepting the idea of limits to growth is subtly revolutionary and contrary to mainstream thought. For a traditional economist, there is no limit to how high GDP may soar, or how high the Dow Jones can fly, or how much wealth can be accumulated. The ecological footprint shatters this notion. If it requires 8 planet Earth's for global population to maintain the same consumption patterns as the United States, then there simply are not enough resources to go around for everyone.

This has implications for global trade. Proponents of free trade promise developing countries that opening their borders will bring growth and prosperity. The underlying assumption is that there is enough wealth to rise all boats. But the ecological footprint analysis says that this simply is not true. Not everyone can consume the same amount, there just isn’t enough water, iron, copper, fish, timber, or fish in the sea for everyone. Under conditions of scarcity, these resources will go to the highest bidder.

And that is exactly what is happening. Wealthy and developed countries are net importers of natural resources while poorer countries are next exporters of these resources. The question remains: how to break this cycle? How do free trade economists reconcile their promise of future wealth with the existing limitations on natural resources?

The only answer is technology and increased productivity. By producing more with less, so the theory goes, we will be able to satisfy everyone’s needs. In that case, developing countries should be more concerned with increasing productivity than with opening their borders.

The point is that that ecological footprint was a useful way to think about how our consumption impacted the planet, and by extension, how our cumulative consumption patterns could not be exported because we face physical constraints.

Three scientific articles and two conversations have forced me to question all that. Moreover, by questioning the idea of an ecological footprint, my conception of sustainability has begun to crumble – or mature. Three teams of researchers have tried to operationalize the ecological footprint idea. In doing so, they have encountered a complex globalized economy. While they came up with hard numbers, the longer one thinks about how to calculate an ecological footprint, the more one realizes that there are too many variables to take into account. (See articles below).

Furthermore, the environmental historian William Cronon, makes it clear that a city’s impact is goes beyond the needs for its residents, but includes people elsewhere because cities serve as central nodes of repackaging and storage to move elsewhere.

Supporters of the ecological footprint can counter-argue that just because humans do not have the capacity to measure an ecological footprint does not mean that it does not exist. There are different consumption patterns that have different degrees and magnitudes of impact on our planet’s ecosystem.

Still, these readings have thrown a wrench into my conception of sustainability. If an ecological footprint cannot measure sustainability, what can? Sustainability cannot be about creating a 100% efficient metabolic cycle - no perfectly efficient system exists, it would violate the laws of thermodynamics-, so at what rate of efficiency do we agree that the process is “sustainable”?

Perhaps I am conceding that sustainable is not as easily defined as I had once believed. I am also conceding several points in a discussion I had with city planner Josep Anton Acebillo, the director of Barcelona’s urban planning agency Barcelona Regional, who argued that sustainability is not as desirable as believed. My idea of a sustainable city was one in which resources were used efficiently, waste was minimized and any waste emitted could be easily assimilated by our ecosystems. This still may be an ideal, but without a method for measuring sustainability such as the ecological footprint, it will be much more difficult to steer our society toward this goal. If we can’t measure our progress, how do we know if we are getting there?


Eaton R.L, G.P. Hammond and J. Laurie 2007. Footprints on the landscape: An environmental appraisal of urban and rural living in the developed world. Landscape and Urban Planning. (83) 13-27.

Folke C., A. Jannsson, J. Larsson and R. Costanza 1997. Ecosystem Appropriation by Cities. Ambio. (26)3:167-172.

Luck M.A., G.D. Jenerette, J. Wu and N.B. Grimm. 2001. The Urban Funnel Model and the Spatially Heterogenous Ecological Footprint. Ecosystems. 4:782-796.