PCDForum Column #65, Release Date November 10, 1993
by William E. Rees and Mathis Wackernagel
Current discussions of the relationship between trade and the environment,
almost universally neglect a fundamental reality. The populations of all urban
regions and many whole nations currently exceed their territorial carrying
capacity. They survive only by appropriating material resources and waste
absorption capacities either from somewhere else through trade, or from future
generations through natural capital depletion. Furthermore, this appropriation
requires that the people living in the "Somewhere Else" be forced or
induced to absorb the related social and ecological costs.
Our calculations suggest that the typical high income urban industrial
region uses the bio-production of 10 to 20 times more land than it covers
spatially. Take our own region, the Vancouver-Lower Frazier Valley Region of
British Columbia in Canada as an example. With current management practices the
average Canadian diet requires 1.1 hectares (ha.) of land per capita for food
production. The forest products consumed require .5 ha. Producing the biomass
equivalent of current per capita fossil energy consumption (or alternatively the
absorption of CO2 emissions) requires 3.5 ha. Thus the 1.7 million people of our
region require at least 8.7 million ha of land in continuous production to
sustain current consumption. Since our valley is only about 400,000 ha, our
regional population "imports" the productive capacity of at least 22
times as much land as it actually occupies. The region is running a massive
As fundamental as this reality is with regard to questions of equity and
sustainability, human societies have not yet developed any means of accounting
for such ecological deficits. It is especially significant that since commodity
flows and trade balances are monitored in monetary, not ecological, units these
ecological deficits are completely ignored in discussions of the costs and
benefits of international trade. Indeed, nations are not even aware of them.
Urbanization and trade have the effect of physically and psychologically
distancing urban populations from the ecosystems that sustain them. Access to
bio-resources produced outside their home region both undermines peoples’ sense
of dependency on "the land" and blinds them to the far-off social and
ecological effects of imported consumption.
Because most products of nature can be so readily imported, and wastes so
easily exported, the population of a given region can expand its consumption
beyond local carrying capacity unknowingly and with apparent impunity by
geographically or spatially discounting ecological costs. The more open the
trading system, the weaker the negative feedback on the consequences of
population growth or increased consumption and the more limited the incentives
for a region to maintain adequate local stocks of productive natural capital.
For example, the ability to import food makes people less averse to the risks
associated with urbanization of locally limited agricultural land. Indeed, by
conventional economic reasoning, if low priced imports undermine the viability
of local agriculture, it becomes rational to convert the land to some other
activity that yields a higher return.
Paradoxically, while trade appears to increase carrying capacity in all
regions, it in fact encourages all regions to exceed local limits by drawing
down "surplus" natural capital stocks. This situation applies not only
to commercial trade, but also to the unmonitored flows of goods and services
provided by nature. Northern urbanites, wherever they are, are now dependent on
the carbon sink, global heat transfer and climate stabilization functions of
tropical forests far beyond their own borders.
The problem is defined by two simple statistics. In 1990 the eco-productive
land area available per capita for the world was 1.7 hectares. The per capita
land appropriation of rich countries to maintain high consumption life styles
was 4 to 6 hectares. In many instances it is trade that makes this imbalance
possible and masks the consequences of over-consumption.
If import dependent regions only drew on true ecological surpluses in the
exporting regions this would not necessarily be a problem. But often they don’t.
Many southern countries are virtually selling the food off their own table,
because much of the Northern land deficit is being made up by encouraging
Southern countries to devote their available productive lands to export crops.
This deprives their people of access to these lands to grow the staples needed
to meet their own basic needs. Those who are displaced move either to
overcrowded cities or to more fragile and less productive segments of the
ecosystem that are quickly taxed beyond their sustainable capacity.
Given the current haste to expand global trade there is an urgent need to
begin accounting for commodity flows and trade balances in ways that illuminate
these realities if we are to move toward a truly sustainable trading system that
serves the long-term human interest. We can no longer afford to base our
decision making in such matters on ecologically empty economic theories.
William E. Rees is a Professor in the School of Community and Regional
Planning, University of British Columbia, Vancouver, Canada. Mathis Wackernagel
is Ph.D. Candidate in the same school. This column was produced and distributed
by the PCDForum based on "Ecological Footprints and Appropriated Carrying
Capacity" to appear in Investing in Natural Capital, Island Press,
Washington, D.C., 1994.