William Rees: Rethinking the City as Complete Human Ecosystem
Stewart Brand called it an environmental heresy to say that cities are green. These days, the apostasy seems to have reversed, and more often than not cities receive environmental praise.
So I was intrigued by the post "Are Cities Sustainable?" by Rex Weyler on the Greenpeace blog. Here is the key part:
Dr. William Rees at the University of British Columbia, who developed the 'ecological footprint' analysis, points out that most cities require the environmental services from a land base 300 to 1000 times the city area. Rees points out that a city is a 'biophysical entity' that includes the complex of land, water, atmosphere, resources, and waste sinks required to support the human population.
Rich consumer cities of Europe and North America require the most ecological space, but all modern cities carry an ecological debt to nature. I live in Vancouver, Canada, which prides itself as being a fairly 'green' city with bike paths and urban gardens, but even so, Vancouver requires a global biophysical area about 390 times the city itself.
In the study Ecosystem Appropriation by Cities published by the Royal Swedish Academy of Sciences, Carl Folke and colleagues estimate that the 29 largest Baltic cities - including Copenhagen, Stockholm, Oslo and Helsinki - appropriate for their resource consumption and waste an area of forest, agricultural, marine, and wetland ecosystems over 560 times the area of the cities themselves. New York requires a total eco-footprint almost 1000 times the city's geographic area. Tokyo requires twice the entire domestic bio-capacity of Japan.
The Folke study shows that the 744 largest cities worldwide require more CO2 sequestration than the entire world's forests could provide. "If the goal is sustainable human settlements," write the authors, "the increasingly limited capacity of ecosystems to sustain urban areas has to be explicitly accounted for in city planning and development."
Here are the conclusions listed by Bill Rees in a 2007 presentation. The slide is titled, "Rethinking the City as Complete Human Ecosystem" (pdf):
If 99%+ of the land that supports cities lies outside their boundaries, shouldn’t we redefine what we mean by ‘urban land’in a whole-systems framework?
A ‘city-as-(eco)system’ would be an urban region comprising both the built environment and as much as possible of the population’s supportive hinterland.
Ideally, it would be politically organized as a modern regional-scale city-state.
Bioregionalism and permaculture provide pre-formed philosophical and conceptual models for human ecosystem planning.
