The Necessity of Eco-Cities

Part 1 An introduction to urban ecology

Don Alexander


Why cities are central to achieving sustainability

By the year 2000, approximately half of the human population will live in cities, yet until a few years ago most discussions of sustainability focused on non-urban systems and on resource issues. This is ironic in light of the fact that, to quote one author, "[c]ities are where most resources are transformed into finished products and consumed." They are also "the prime focus for the generation of waste and other pollutants that impact non-urban areas." A good example of the environmental significance of cities is the problem of global warming. Global warming is overwhelmingly the result of emissions from private automobiles, and the vast majority of these are concentrated in cities.

To take this example one step further, the predominance of private transportation can be directly linked to patterns of land use in the built environment. Where cities are spread out, it becomes difficult to use mass transit cost-effectively and people are forced to commute to work and to shopping. This underscores the importance of what Richard Register calls the eco-city insight: a recognition "that the structure of the built habitat is the foundation of environmental and social success and failure." He suggests that this insight is almost completely missing from the current debate.

Ted Fowler, a planner and writer from Toronto, makes a similar point: "[w]hen local officials talk about what they are doing to support the environment, they point to recycling programs, tree plantings and banning [CFCs]. And while such policies are significant, they ignore the basic patterns of land use which must be changed before our cities can be ecologically sensible settlements."

Over the past decade, researchers and activists have begun to address these issues, and much of this discussion has occurred under the phrase of "sustainable urban development." This literature is concerned with the environmental impacts of our current cities; with what sustainable cities might look like in a more ideal world; and with what policies, plans, and actions might help us get there. In addition to the work of policymakers and academics, there is also the on-the-ground work of thousands of urban dwellers both North and South who, through their activism, are demonstrating in an embryonic form many of the solutions that are needed to transform our cities.

Obviously, the problems in the cities of the North and South are quite different. In the cities of the North, the problems are largely those of affluence and over-consumption, though many people are still victimized by poverty and a lack of access to adequate services. In the South, many of the urban environmental problems are the result of poverty and overcrowding, though there is also a wealthy stratum whose lifestyles mimic those of people in the rich countries. All of this suggests that the challenges involved in making the transition to sustainable cities involves not only changes in technology and infrastructure, but also changes in the distribution of wealth and in the cultural attitudes that foster overconsumption in the North, and rapid population growth and urban flight in the South.

Another way in which cities are important to the achievement of sustainability lies in the impact that the built environment has on what might be called "the cultural prerequisites for sustainability." In order for people to be part of the solution, rather than part of the problem, citizens - all of us - need to feel a sense of community with our fellow humans, need to feel that we can participate in and shape the decisions that affect our lives, and need to recognize our dependence on natural systems and the important role that nature, both on a material and a spiritual level, plays in our lives. If we are alienated socially, politically, and ecologically it will be very hard for us to contribute to achieving a sustainable society.

It can be argued that the way cities are built has a lot to do with whether, in fact, people feel alienated. This dimension of the issue has somewhat been ignored by those who have written about the ecological impacts of having relatively more or relatively less dense cities. The challenge, really, is how do we create cities that are ecologically efficient and relatively benign, but which also enhance the quality of life for the people living in them, while at the same time ensuring a more equitable sharing of resources between people.

A good example of how these issues can get tangled is in relation to neighbourhood density. Many people in the Vancouver region enjoy living in single family neighbourhoods or suburbs, even though they contribute to making affordable housing scarce, are more expensive to service, consume more land, promote urban sprawl, and make mass transit options more difficult to implement. Despite the fact that European cities - which are renowned for their quality of life - are much denser than Canadian cities, it is very difficult to sell people on giving up the suburban ideal.


The concept of an urban ecosystem

One of the ideas that researchers and activists have used to make sense of these issues is the "urban ecosystem" concept. Basically, cities can be seen as functioning like ecosystems. Neither natural ecosystems nor urban ecosystems are closed systems; they are both dependent on outside inputs in order to function. These include sunlight, water and some outside nutrients, in the case of natural ecosystems, and a number of life support systems in the case of cities. One way of thinking about this is what would happen if one were to put a glass or Plexiglas bubble over a city. How long would it be able survive? What are the inputs that cities require, and what outputs does it generate that it needs to get rid of?

To get a better sense of the differences between natural and urban ecosystems, let's look at some of the ways that cities transform the natural environment over the course of their development. First of all, there are the inputs and outputs that are needed or generated by a city - such as fresh air, water, food, energy, raw materials, and various forms of pollution and solid waste. In addition to the "throughput," we can classify the impacts of cities into four main areas: those that affect land, those that affect water, those that affect air, and the impact in terms of energy and raw materials - as follows:


  • loss of forest cover
  • grading of landforms, soil erosion and compaction
  • loss of large mammals and biodiversity, including the introduction of "exotics"
  • loss of farmland


  • filling in and culverting of streams and wetlands/ loss of fish habitat
  • eutrophication, siltation, and introduction of garbage into stream courses
  • toxic run-off and misuse of storm sewers
  • loss of percolation
  • excessive water demand
  • contamination of bays, inlets and rivers
  • dyking of rivers


  • destruction of oxygen-producing and pollution-absorbing vegetation
  • industrial and transportation smog
  • particulate pollution
  • relationship of air pollution to sprawl
  • sulphur dioxide and nitrous oxide, leading to acid rain and ground-level ozone pollution

Energy and Raw Materials

  • transition from solar power to fossil fuels and hydro-power
  • massive consumption of raw materials
  • urban heat island
  • solid waste problems

An understanding of these impacts leads to the concept of the "ecological footprint," first developed by Bill Rees and Mathis Wackernagel at the University of British Columbia. Basically, what `ecological footprint´ theory says is that city dwellers, particularly in the relatively wealthy countries of the North, borrow or appropriate carrying capacity from other regions of the globe. Many of the food items and raw materials that we use in our daily production and consumption come from elsewhere, and usually the environmental degradation that accompanies the growing of food or the extraction of raw materials stays in the region where these products are produced. Not only that, but cities often export their pollution and waste products to other regions, forcing other people to live with the consequences of our activities.

Kirkpatrick Sale once wrote, and these figures are out of date now, that a "city of one million... takes in 9,500 tons of fossil fuels, 2,000 tons of food, 625,000 tons of water, and 31,500 tons of oxygen every day - and puts out 500,000 tons of sewage, 28,500 tons of carbon dioxide, and great quantities of other solid, liquid, and gaseous wastes. The contemporary high-rise city," he says, "is an ecological parasite as it extracts its lifeblood from elsewhere and an ecological pathogen as it sends back its wastes."

It is estimated that the people living in the Greater Vancouver region, for instance, require 18 times more land to sustain themselves - that is, to provide needed resources and to assimilate wastes, many of which are not adequately assimilated now - than the area they currently occupy.

A good example of the ecological footprint is the damage inflicted on the environment and on Native people by the massive hydro dams in the hinterlands of B.C. whose energy is siphoned off to run our cities, the air pollution from cars that is generated in the Vancouver area, when is then carried by wind up the Fraser Valley to Chilliwack and Hope, or else carried up into the atmosphere where it contributes to the problem of global warming or acid rain, or the garbage from Vancouver that is shipped out to Cache Creek.

As mentioned earlier, natural ecosystems are not closed systems. Not only do they depend on external solar energy, their permeable boundaries allow for the movement of water, nutrients, sediments, and species from one ecosystem to another. But, despite this, natural ecosystems are relatively self-sufficient, something that the contemporary city is not. Of course, if we define cities as those areas in which the built environment predominates over the natural environment - even the modified natural environment that is forest land or farmland - then urban ecosystems will never strictly be self-sufficient.

But if we define a city-region as encompassing the area that is in close proximity to the city, as was the case with the old city-states of Greece and medieval Europe, then in theory there's no reason that cities couldn't at least be somewhat self-sufficient. And, for some people, this is the definition of a sustainable city - one that does not drain carrying capacity away from other parts of the world and which does not contribute to a deteriorating global environment through ozone depletion or global warming.


Competing visions of sustainable cities

Ever since radical planners and ecologists came on the scene - say, within the last 100 years - and especially with the rise of the literature on sustainable urban development, there has been debate over exactly what a sustainable city would look like, and over how we go about achieving it. Partly this is a debate over competing visions or ideals, and partly it is a debate over practical considerations and social justice.

Many of the people who have written about ecologically sound cities have been motivated by more than ecological concerns. They have wanted to create cities that have a sense of human scale, where people can easily get to know one another, where they can develop a strong sense of kinship; where participation is relatively easy to accomplish and people can meet to discuss issues of common concern in a face-to-face setting; and where nature is not something remote, but permeates people's lives, along with the seasons, the cycles of vegetation, and the migrations of birds and animals.

Traditionally, this decentralized city is the ideal of the ecology movement. It is one that is favoured by many anarchists and by those who seek an optimum quality of life. However, things have changed somewhat since this ideal was first put forward. The earth now contains 5.8 billion people, attempts at limiting urban growth - even in authoritarian societies such as the Soviet Union - have proven fairly ineffectual, and there are those who say that, if we spread the human population out in a decentralized way, we will create even more devastation. They believe that, only by penning people up in large, relatively high-rise, cities can we spare the farmland that we need to grow our food and protect tracts of wilderness, thereby conserving biodiversity.

Moreover, many of these people argue that big cities are more innovative and cosmopolitan, that their efficiency in using energy and raw materials is greater than that of small settlements, and that massive population concentrations are necessary in order to underwrite the costs of mass transit, sewage and waste treatment, and so on. They also argue that trying to halt city growth - or dispersing populations to the countryside - could only be accomplished by dictatorial means, and that halting immigration or freedom of movement is potentially racist and a violation of social justice.

Thus, we see the major division on the subject of sustainable cities - between decentralist and centralist positions - with many gradations in between. Each embodies a different ideal: decentralists favour self-reliance and centralists favour efficiency. Each side has some points to its credit. Giant cities are potentially alienating places, and people in them tend to assume their food comes from the supermarket and their garbage and sewage simply go `away.´ Moreover, if cities are already exceeding the carrying capacity of their respective regions, and are borrowing resources from elsewhere, it's hard to see how continuing to allow them to grow - even if they do become more efficient consumers and generators of waste - is going to solve the problem.

On the other hand, spreading the human population out in a web of smaller settlements would potentially put more areas of the earth at risk, and stopping the growth of cities and forcing resettlement could very well require policies that would be racist and authoritarian. So, what can we do? In the next installment, we will look at some of the innovative measures that have been advocated, and in some cases implemented, for making cities more sustainable places to live that borrow elements from both of these schools of thought.