By William E. Rees
June/July 2006
For the first time in history, more than half of humanity now lives in cities. But just how sustainable are the world’s cities—-both rich and poor?
LONDON. ROME. Sydney. Tokyo. Even for people who have never visited them, the mere mention of the world’s great cities leaves many of us itching to pull up roots and go there to experience what they have to offer. Even my hometown of Vancouver draws people from all over the world, and can justifiably bask in the glow of its on-going recognition as “the world’s most livable city.”
But there is another side to cities and their gravitational pull, which is only too evident in the swelling slums and barrios of cities as far flung as Jakarta, Lagos and Rio de Janeiro. The world is currently experiencing the greatest human migration in history—-a worldwide rural-to-urban migration that has swelled the population of the world’s cities by fifty percent, from two billion in 1985 to three billion in 2002, and which is expected to add another 2.2 billion people to the world’s cities by 2030. This means that in just three decades the urban population alone is expected to grow by the equivalent of the total human population in the early 1930s. Think about it: cities will add more people in thirty years than the planet had accumulated in the previous 2.5 million years of hominid history! And most of this explosive growth will take place in the poorest of the world’s cities, adding millions of people to their already overcrowded slums.
All of which raises a critical question: in an age of allegedly “sustainable development,” just how sustainable are the world’s cities, both rich and poor?
To some analysts, this question is silly, even meaningless. They argue that people come to cities to take advantage of economic opportunities, to better themselves (ignoring the fact that many of the rural poor are actually being kicked off their land, victims of the land consolidation demanded by “structural adjustment”). These experts agree that the barrios are social disasters but argue that slums are temporary, a transitional phase that will be eliminated by economic growth. Just look at the seeming wealth creation that has lifted so many Chinese cities from the poverty mire in the past quarter century.
Appalled by pollution? No problem, say such analysts. Once people get rich enough to care about air and water quality, they’ll deal with it. In the words of economist Wilfred Beckerman, “the surest way to improve your environment is to become rich.”
Worried about resource shortages? No issue here either, now that technology can substitute for nature and thus decouple the economy from the ecosphere. As Nobel lauriate economist Robert Solow famously put it over thirty years ago, “If it is very easy to substitute other factors for natural resources, then—- the world can, in effect, get along without natural resources, so exhaustion is just an event, not a catastrophe.”
But is escaping our natural limits really that easy? Can economic growth and technological prowess really fill all the potential potholes on the road to global sustainability? If we look more closely at the biophysical and ethical dimensions of the problem, we will see that the answer is no.
First, what do we mean by sustainability? Analysts often avoid this question because of ongoing debate over the many conflicting interpretations. This is unhelpful because we do need criteria and standards against which to measure progress. On the simplest level, then, let me propose that something is sustainable if can safely remain in its present state or maintain its present course indefinitely. Thus, a sustainable society might be one that is experiencing positive social, cultural and economic change—-i.e., development—-that does not degrade the ecosystems upon which that society is dependent. Note that development, as defined here, can occur with or without growth in the economy. (Development means getting better; growth means merely getting bigger. The fact that we have confused the two for so long goes a long way toward explaining the nature of the environmental and social problems we face.)
But how can we determine whether a society is over-using its critical ecosystems? We can begin by applying ecological footprint analysis, a quantitative tool I pioneered with my students at the University of British Columbia. The “ecological footprint” of a given population is the total area of terrestrial and aquatic ecosystems required, on an ongoing basis, to produce the resources that the population consumes, and to assimilate the wastes that the population produces, wherever on earth those ecosystems are located. Thus, a community that consumes large amounts of energy and material resources will have a substantially larger ecological footprint than an otherwise similar community that uses fewer resources.
“The ecosystems that support city-dwellers� consumer lifestyles are often located in other countries half a world away.”
How does the ecological footprint of our cities measure up? It turns out that the residents of the world�s rich cities require the life support services of five to ten hectares (twelve to twenty-five acres) of global average productive ecosystem per capita, compared to the half hectare demanded by the poorest of the poor. By this measure, in 2001, greater Vancouver’s 2.1 million residents had an aggregate ecological footprint of almost fourteen million hectares. This is forty-eight times the size of the Greater Vancouver Regional District, or about twenty times the area of the entire Lower Fraser Valley.
If this seems mind-bogglingly unsustainable, consider the world’s largest metropolis. Tokyo’s thirty-three million residents—-about a quarter of the country’s population—-have a collective ecological footprint of 142 million hectares, or 1.6 times the equivalent productive capacity of their entire country! In short, Japan could not sustain even its capital city at current material standards if it had to rely solely on the output of its domestic ecosystems. These data show that Japan—-along with most other wealthy consumer societies—-has overshot its domestic carrying capacity and is running a massive “ecological deficit” with the rest of the world.
In effect, ecological footprint analysis shows us that, while modern urbanites may reside in cities, they do not actually live there in ecologically meaningful terms. The ecosystems that support wealthy city-dwellers� consumer lifestyles are often located in other countries half a world away. For example, most of the pollution generated by China�s factory cities is attributable not to newly-urbanized Chinese, but rather to consumption by people living in high-income cities like London, New York and Vancouver. It seems that far from decoupling humanity from nature, technology serves largely to extend the scope and intensity with which humans exploit ecosystems everywhere—-and globalization gives the rich access to just about everyone else’s ecosystems.
With every increment of economic growth, the human ecological footprint expands. So it is that modern high-income cities have become ravenous parasites on the global hinterland. And to complicate matters, the separation of production from consumption renders complacent urbanites both blind to the degradation resulting from their consumer lifestyles and unconscious of their increasing dependence on a deteriorating resource base.
This is no small problem because the entire planet is in a state of overshoot. The urbanizing human enterprise, losing touch with its ecological roots, is destroying the habitat on which it depends. The average human ecological footprint is 2.2 hectares, but there are only 1.8 hectares of truly productive land and water ecosystems remaining per person on Earth. To bring just the present world population up to average North American material standards, would require four additional Earth-like planets!
Ecological footprint analysis thus provides a biophysical standard measure for sustainability—-our current “fair share” of 1.8 hectares per capita—-and this in turn suggests an ethical directive for people concerned about sustainability: No lifestyle is sustainable if it could not safely be shared by all members of the human family. Vancouverites may be justifiably proud of the region’s numerous innovative sustainability initiatives, but until we have made significant progress toward reducing our average ecological footprint from almost seven to a sustainable 1.8 hectares, this “most liveable” of cities will remain one of the least sustainable on Earth.
William Rees, PhD, has taught at the University of British Columbia�s School of Community and Regional Planning (SCARP) since 1969-70. Founder of SCARP�s Environment and Resource Planning concentration, Professor Rees is best known for inventing “ecological footprint analysis.” His 1996 book on the subject Our Ecological Footprint (co-authored with then-PhD student Mathis Wackernagel) is now available in nine languages.
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