Have you ever asked yourself: How
much of the Earth is dedicated to sustaining just me? Not many of us have
urbanization, trade, and technology have alienated modern urbanites from the
land. The fact is, however, that the 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 themselves, but also to build and maintain the
consumer and capital goods, the factories, the service infra-structure all the
accoutreme nts 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 to far exceed our biological demands on the
ecosphere. As a result, popular illusions notwithstanding, people today are
more dependent on natures services than at any previous time in history. The
material flows necessary to sustain our consumer lifestyles and our cities make
direct and indirect claims on land and ecosystems all over the Earth. By
estimating these physical appropriations, my students and I have shown that the
citizens of high income countries typically use the output of between three and
five hectares of ecologically productive land per capita. It is a simple step
from there to estimate the true ecological footprint (EF) of a whole city,
region, or country. 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 all the resources consumed, and to assimilate all
the wastes produced, by that population, wherever on Earth that land is
located.
Why Cities Aren’t Where They Are Shown
On The Map?
Wealthy cities and countries prosper
by appropriating the carrying capacity of an area vastly larger than the spaces
they physically occupy. For example, the Canadian city of Vancouver had a 1991
population of 472,000 and an area of 114 km2 (11,400 hecta res). With a per
capita land consumption rate of 4.3 hectares, Vancouver s residents require
(conservatively) two million hectares of land to support current consumption
levels. However, the area of the city is only 11,400 ha. This means that the
city’s p opulation uses the productive output of a land area nearly 180 times
larger than its political area to maintain its consumer lifestyle. If we add the
aggregate marine footprint (.7 ha/capita), the total becomes 2.4 million
hectares or over 200 times the size of the city. These results are fairly
typical. The UK’s International Institute of Environment and Development
estimates that London’s ecological footprint for food, forest products, and
carbon assimilation to be 120 times the surface area of the city proper.
Researchers at Stockholm University report that the aggregate consumption of
wood, paper, fibre, and food (including seafood) by the inhabitants of 29
cities in the Baltic Sea drainage basin appropriates an ecosystem area 200
times larger that the cities themselves (the later study does not include an
energy component.)
These data show that as a result of
enormous increases in per capita energy and material consumption, and growing
dependencies on trade, the ecological locations of cities no longer coincide
with their geographic locations. 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. Cities may be the engines of economic growth and the brightest stars in
the in the constellation of human achievement. 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.
Toward Urban Sustainability
For deep structural and ideological reasons, continued GDP 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 (only 2-3% growth per year). Scientists agree
that in these circumstances, resource use a nd environmental impact per unit
consumption in high income countries must be reduced by up to 90% if we are to
achieve sustainability fairly within the planet's ecological means. Cities
present both unique problems and opportunities in closing this sustainability
gap. Perhaps the most significant problem is that cities typically disrupt the
biogeochemical cycles of vital nutrients and other chemical resources. 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 goes straight
out to sea. Agricultural soils are therefore degraded (half the natural
nutrients and organic matter from much of North America since 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
urbanization and a redefinition of economic efficiency. On the plus side, the
sheer concentration of population and consumption gives cities considerable
leverage in reducing their ecological footprints. Properly planned,
urbanization can mean: lower costs per capita of providing piped treated water,
sewer systems, waste collection, and most other forms of infrastructure and
public amenities; greater possibilities, and a greater range of options, for
material recycling, re-use, re-manufacturing, and the specialized skills and
enterprises needed to make these things happen; high population densities which
reduce the direct per capita demand for 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.
For a fuller appreciation of urban
leverage, particularly in auto-dependent cities, lets examine this last option
in more detail. Various estimates place suggest that the direct and indirect
public subsidy to private cars is as much as $US 2500 per year. Suppose we
gradually move toward full cost pricing of urban auto use and reallocate a
significant proportion of this subsidy to public transit. This would make
public transportation faster, more convenient, and more comfortable than at
present, and vastly cheaper than private autos. City residents would demand
improved public transit with the same passion they presently reserve for
expanded roadways. The resultant shift in modal split would not only be
ecologically more sustainable but also both economically more efficient and
socially more equitable. (It should therefore appeal to both the political
right and left.) Over time, it would also contribute to better air quality,
improved public health, greater access to the city, more affordable housing,
more efficient land use, the hardening of the urban fringe, the conservation of
food lands, and levels of urban density at which at least direct subsidies to
transit become unnecessary. In short, because of complex systems linkages,
seriously addressing even a single issue can affect many factors contributing
to urban sustainability and livability. I call this positive feedback effect
the urban sustainability multiplier.
Finally, we should recognize here
that many of the environmental demands and impacts that can be traced to cities
have 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 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 urbanization should be encouraged or resisted. In the
meantime, we clearly must liberate ecological space for the world’s poor. It
seems that the wealthy have a moral obligation both to make their cities more
ecologically benign and to reassess their private consumption patterns.
From People and Planet Magazine
William E. Rees,
University of British Columbia
School of Community and Regional Planning
University of British Columbia
School of Community and Regional Planning
