Urban Ecosystems

Cities of the future will embrace the ecology of the landscape,
rather than set themselves apart

One of the articles in Designing A Sustainable Future (IC#35)
Originally published in Spring 1993 on page 43
Copyright (c)1993, 1996 by Context Institute

John T. Lyle is professor of landscape architecture at California State Polytechnic University, Pomona, and acting director of the Center for Regenerative Studies. This article includes excerpts from his book
Regenerative Design for Sustainable Development, to be published this year by John Wiley and Sons, Inc., and portions of an address delivered to the International Symposium on Cities in Coexistence with the Earth, sponsored by the Council on Urban Ecosystems, Osaka, Japan, September 14, 1990.

For thousands of years, cities have existed apart from nature. Why should we begin now to think of cities in terms usually reserved for the natural environment?

The fact is, in the world that we’ve created for ourselves, cities occupy pivotal positions, for better or worse, in the patterns of global ecology. This becomes clear when we put aside our standard images of cities and consider their ecological functions.

Cities of the industrial era have consciously excluded natural processes, substituting mechanical devices made possible by intensive use of fossil fuels. Rather than using the solar energy continuously falling on their streets and buildings, they dissipate it as excess heat. At the same time, they import immense quantities of concentrated energy in various forms, most of it derived from petroleum coaxed from the ground in distant landscapes.

They rush the water falling upon their roofs and streets as rain out through concrete pipes and channels into the nearest bay or river and, at the same time, bring water in from distant landscapes through similar concrete channels.

From outer landscapes, too, they import nutrients in the form of food, use it once, then send it out through pipes as sewage waste.


If we think of the industrial city at the simplest possible level in systematic terms, we can visualize it as a system of one-way flows of energy and materials. The flows proceed from sources in the outer landscape, to production and consumption in the city, to waste sinks in the air, water, and land.

Among the sources are farms, forests, mines, oil fields, and large areas of the oceans. Sinks are in both the upper and lower atmosphere, where the by-products of combustion tend to accumulate; in lakes and bays, where we usually put our sewage wastes; and in the land, where we bury garbage and chemical and nuclear wastes. Altogether, the sources and sinks include virtually the entire Earth.

We might see our overwhelming problems of depletion and pollution as largely outgrowths of our ways of shaping the urban environment. Sources are continuously depleted and have few means of regeneration because the materials that might otherwise replenish them are going into distant sinks. The sinks are continually overfilled because their natural capacity to assimilate energy and materials is far exceeded by the concentrated quantities being put out from the cities.

Although the global system of one-way flows took shape during the industrial period – that is, over the past 200 years – one-way flows of smaller dimensions have existed in various forms at least since the origins of agriculture some 10,000 years ago. From the perspective of that time, both sources and sinks looked unlimited. Now we know better, but changing such ancient patterns will not be easy. It will require us to rethink our patterns of production and consumption, as well as our concepts of waste. Most dramatically, it will require that we rethink our ways of designing cities.


If we concern ourselves with the materials of primary life support – water and nutrients – the medium for recycling in the city, as in nature, is the landscape. In cities of the future, the working landscape becomes the unifying, integrating network of urban form, rather than a decorative addition as in the industrial city.

The urban landscape collects water when it rains and holds it in ponds or tanks for future use or allows it to infiltrate slowly into underground storage. Thus, the surface will be sculpted with swales and retention ponds, some holding water through the year, some usually dry.

The working landscape also processes water – both sewage and water polluted by contact with roofs or streets – filtering it through plants in ponds and wetlands. Plants and microorganisms assimilate nutrients and other materials, recycling them through the landscape and in many cases eliminating the need for a mechanical treatment system.

The same working landscape that filters, assimilates, and stores water and nutrients also serves to filter, cool, and direct the flow of air. Masses of trees are located around heavily traveled streets, industrial plants, and other sources of air pollution, where they assimilate some pollutants, such as carbon dioxide, and produce oxygen. They also create micro-climates within the city.

Food production also becomes an important part of the urban landscape. Just how great the potential for growing food actually is remains a question, but the examples of Chinese cities show that urban farms can produce a great deal of food. And certainly the biomass produced can be used in a great many ways – for composting, for energy, and for making other products.

As we shift to regenerative energy sources, we can also expect to see energy generating apparatus appearing in the urban fabric.


Making visible the ecological processes that support life is an important part of this emerging landscape. The child who grows up in a regenerative city of the 21st century will know very well where the water she drinks comes from and where her wastes go. She will have an inner feeling for the atmospheric fluxes that make cool and warm places, and she will know how food grows and in what season. All this will be part of her daily experience.

She will also know that the same landscape that accomplishes all this provides a place to run, to play hide-and-seek or baseball, and to ride her bicycle to the grocery store. In the same landscape, she will see birds and squirrels and snakes, all as inhabitants of the same world she lives in.

Within this green matrix, communities form identifiable neighborhoods. Though cities will continue to spread over the landscape, we can hope that with planning, the undifferentiated metropolis of the industrial era will give way to a pattern of discrete, identifiable, interrelated communities, joined together by the working landscape.

If this happens, transportation will again have a great deal to do with it. The need to use less energy will make it more desirable to walk or ride a bicycle to schools, shops, meeting places, and local services. This will pull residential, commercial, and civic areas closer together.

Roads, like virtually all the elements of the landscape, will feature multiple uses accommodating pedestrians and bicyclists as well as cars.


In regenerative cities, buildings will be elements of the landscape like hills or lakes or groves of trees, rather than discrete objects standing apart from the landscape. Within the green matrix, they will cluster more tightly together than the buildings of industrial cities. Rather than asserting themselves and competing for attention, they will blend together more in the manner of a medieval town, forming harmonizing clusters that reflect a sense of interrelationship and community, as well as a sense of rootedness in the earth. Structures within each cluster will be close enough together to avoid wasting land and to minimize circulation routes, but far enough apart to allow for sunlight and air movement.

The buildings in a particular locale will have similar forms, reflecting the climate and landscape. Buildings in the desert are likely to merge into the earth, exposing little of their skins to the desiccating sun, while buildings in the tropics will generally rise above the water-laden ground into cooling breezes.

In every climate, rooftops can be fertile and productive. Their walls can be sheathed in living green as well. In most climates, buildings will turn transparent faces towards the sun, with a variety of adjustable shading devices moving and casting shadows that vary through the seasons. The sizes of individual structures will vary from high-rise structures to single-family houses. The mass of each building will be relatively small, however, to allow for cross ventilation and natural lighting in every space.

Within each cluster, or local neighborhood, uses will be mixed. Dwellings, shops, offices, and schools will be close together, sometimes within the same structure or grouped around a plaza or courtyard. Sizes and shapes of neighborhood clusters will vary, especially since most will evolve out of cities first built during the industrial period. Within the clusters, outdoor spaces will be relatively small, scaled for human activity, in contrast to the larger areas of the green matrix that envelope each cluster and knit them all together.

Within the green urban matrix, local communities are likely to vary greatly in character and density. Cities everywhere, but especially American cities with their enormous ethnic and social diversity, have always featured distinct neighborhoods identified with distinct cultures.

Densities can vary from highly concentrated mid- to high-rise communities to dispersed communities made up of single-family homes. Though such cities will spread over the landscape, they can be designed to embrace the ecology of the landscape rather than obliterating it. Nature’s processes can continue to function in concert with human culture. In such a future, the conflicts between nature and culture that characterized the industrial era will no longer exist.