Ecological footprints of the future

Posted: 12 June 2001

Author: Dr William Rees

Teacher, researcher and founding member of Canada's foremost environmental NGO, Pollution Probe, Dr William Rees has pioneered the concept of 'ecological footprint' analysis. This provides a way to estimate the biophysical load of cities, regions and whole countries on the ecosphere. Here Dr Rees warns that a major shift in values and consumption habits is essential both for moral reasons and to prevent our heavy footprints from destroying the earth's carrying capacity.

Have you ever asked yourself: "Just how much of the Earth is dedicated to sustaining just me?" Not many of us have - people today simply do not think of themselves as ecological entities. Urbanisation, trade, and technology have alienated modern urbanites from the land.

The fact is, however, that the ecological ties that bind have never been stronger. High income urban societies require a constant input of material and energy from nature not only to feed their citizens, but also to build and maintain their consumer and capital goods, the factories, buildings, machinery, service infrastructure - all the accoutrements of modern life.

The waste burden has, of course, increased proportionately. In fact, since the beginning of the industrial revolution, our industrial metabolism has grown so that it now far exceeds human biological demands on the ecosphere. As a result, popular illusions notwithstanding, people today make greater demands on nature's services than at any previous time in history.

Thirty years ago, American ecologist Eugene Odum wrote: "Great cities are planned and grow without any regard for the fact they are parasites on the countryside which must somehow supply food, water, air and degrade huge quantities of wastes." Indeed, with globalism and expanding trade, the material flows necessary to sustain our consumer lifestyles make direct and indirect claims on land and ecosystems all over the Earth. illustrationIllustration: © Phil Testemale, from, Our Ecological FootprintEco-footprint analysis enables us to estimate the extent of this global urban "parasitism". We define the 'ecological footprint' of any specified population as the total area of productive land and water required on a continuous basis to produce the resources that the population consumes and to assimilate the wastes that the population produces, whereever on earth the relevant land and water are located. Various case studies show that the citizens of high income countries typically use the output of between four and ten hectares of ecologically productive land per captia. It is a simple step from there to estimate the ecological footprint (EF) of a particular city or urban region.

The city's global hinterland

Eco-footprinting shows that wealthy cities and countries prosper by appropriating the carrying capacity of an area vastly larger than the spaces they physically occupy. For example:

  • The author's home city of Vancouver, Canada, had a political-geographical area of 11,400 ha and a population of about 472,000 residents in 1997. Using the Canadian average ecological footprint for food, fibre, and carbon sinks of about seven hectares per capita we can estimate that the aggregate eco-footprint of Vancouver city is 3,304,000 ha, or 290 times its nominal area.

  • In 1998, researchers in Toronto, Canada estimated a per capita ecological footprint of 7.6 ha for that city. Thus the 2,385,000 residents of Toronto proper have an aggregate eco-footprint of 18,126,000 ha, an area 288 times larger than the city's political area (63,000 ha).

  • In a more comprehensive study using region-specific data, researchers at the university of stockholm estimate that the 29 largest cities of Baltic Europe appropriate for their resource consumption and waste assimilation, an area of forest, agricultural, marine, and wetland ecosystems 565-1130 times larger than the area of the cities themselves.

These results are fairly typical and their implications are sometimes startling. A study by the International Institute of Environment and Development in london estimates that the food, forest products, and carbon assimilation footprint of London alone is approximately equivalent to all the productive land in the UK!fuelwoodTaking fuelwood to market, Ivory Coast© Mark Edwards/Still PicturesSuch data shows that as a result of enormous increases in per capita energy and material consumption, and growing dependence on trade, the ecological locations of large human settlements no longer even remotely coincide with their pinpoint locations on the map. Modern high-density settlements necessarily appropriate the ecological output and life support functions of distant regions all over the world through both commercial trade and natural biogeochemical cycles.

Great cities are among the brightest stars in the in the constellation of human achievement and they have become the engines of national economic growth. However, they also resemble entropic black holes, sweeping up the output of whole regions of the ecosphere vastly larger than themselves.

Perhaps the most important insight from this result is that no city or urban region can be sustainable on its own. Regardless of local land use and environmental policies, a prerequisite for sustainable cities is sustainability of the global hinterland.

Urban sustainability

For deep structural and ideological reasons, continued economic growth in both the North and South remains virtually unchallenged as a goal of global 'sustainable development'. Meanwhile, various studies suggest that even the present level of aggregate consumption exceeds the long-term human carrying capacity of the Earth. Let's assume a near-doubling of population and a quadrupling of world output over the next 50 years (this requires only 2-3 per cent growth per year). Scientists agree that in these circumstances, resource use and environmental impact per unit of consumption in high income countries must be reduced by up to 90 per cent if we are to achieve sustainability fairly within the planet's ecological means. pollutionHeavy pollution from steelworks, Jamshedpure, India© F.N. Petit/Panos PicturesCities present both unique problems and opportunities in closing this sustainability gap. In addition to their massive ecological footprints, modern cities typically disrupt the biogeochemical cycling of vital nutrients and other chemical resources through the very ecosystems upon which they depend. Removing people and livestock far from the land that supports them prevents the economic recycling of phosphorus, nitrogen, other nutrients and organic matter back onto farm and forest land. As a consequence, local, cyclically integrated ecological production systems have become global, horizontally disintegrated, throughput systems.

For example, instead of being returned to the land, Vancouver's daily appropriation of Saskatchewan mineral nutrients (in the form of various grain-based products) eventually goes straight out to sea as part of the city's sewage. Agricultural soils are therefore degraded (half the natural nutrients and organic matter from much of North America's once rich prairie soils have been lost in a century of mechanized export agriculture) and we are forced to substitute non-renewable artificial fertilizer for the once renewable real thing. This further damages the soil and contaminates water supplies.

All this calls for much improved accounting for the hidden ecological costs of urbanisation and a redefinition of economic efficiency. Given that at least 99.5 per cent of the land that cities occupy in ecological terms lies outside their boundaries, perhaps we should even rethink what we mean by 'urbanised' land.

On the plus side, the sheer concentration of population and consumption gives cities considerable leverage in reducing their ecological footprints. Properly planned, urbanisation can mean:

  • re-use, re-manufacturing, and the specialized skills and enterprises needed to make these things happen;
  • high population densities which reduce the per capita demand for directly occupied land;
  • more opportunities through economies of scale, co-generation, and the use of waste process heat from industry or power plants, to reduce the per capita use of fossil fuel for space-heating;
  • great potential to reduce (mostly fossil) energy consumption by motor vehicles through walking, cycling, and public transit.

Liberating ecological space

Keep in mind, however, that 65 per cent of environmental demands and impacts that can be traced to cities has nothing to do with the structure, form, or other inherent properties of cities per se. Rather, they are a reflection of societal and individual values and consumer behaviour. These impacts would occur regardless of settlement pattern.

For example, if an individual's personal consumption demands the continuous output of four hectares of land scattered about the globe it doesn't much matter where that individual resides. Thus, the issue here is whether the unique properties of cities make them inherently more or less sustainable than alternative settlement patterns. Until we know the answer to this question, we cannot know whether further urbanisation should be encouraged or resisted.

In the meantime, we clearly must liberate ecological space for the world's poor. There are only about two hectares of ecologically productive land and aquatic ecosystems per capita on earth. This means that the citizens of high income countries 'appropriate' of two to five times their equitable share of the world's ecological output. It seems that in these circumstances the wealthy clearly have a moral obligation to make their cities more ecologically benign and as part of this they will have to reassess their private consumption patterns.

Dr William Rees has taught at the University of British Colombia since 1969 and is currently a Professor in the School of Community and Regional Planning. He served as director of the school from 1993 to 1999. His latest book, co-authored with Mathis Wackernagel, is Our Ecological Footprint: Reducing Human Impact on the Earth, New Society Publishers, Gabriola Island BC and Stony Creek, CT.Related link:How Lightly Do You Tread Upon This Earth?