Summer 2001 ■ 19 Gray City, Green City New thinking and new settlement patterns can bring about urban sustainability. BY MARK DEKAY AND MICHEAL O’BRIEN BY MARK DEKAY AND MICHEAL O’BRIEN BY MARK DEKAY AND MICHEAL O’BRIEN BY MARK DEKAY AND MICHEAL O’BRIEN BY MARK DEKAY AND MICHEAL O’BRIEN T he American city, if one can still call such a sprawling, gray metropolis a city, is an ecological disaster. The way cities use land and re- sources profoundly alters the qual- ity of the local and global environ- ment. Uncontrolled growth devours land, water, and energy from the surrounding landscape. Contempo- rary settlement patterns create auto dependence, high energy demands for buildings, water pollution from excessive toxic runoff, air pollution, and such other adverse environmen- tal effects as increased health risks caused by coal mining, nuclear waste, and fuel burning. For their exorbitant ecological price, these urban patterns do not even buy a high quality of life. Early 21st century Americans are sepa- rated from the aesthetic and ecologi- cal experience of nature while spending hours every day commut- ing and several more hours work- ing to pay for their cars. Neighbors are not friends, community is not tied to place, and millions, too poor to own cars, are disenfranchised. The city is noisy, congested, frus- trating, and unhealthy. Our society has created this habitat for our- selves. In addition to the global macro- ecological problems caused by or contributed to by cities, current settlement patterns create a host of local ecological problems. Wildlife habitat in cities is scarce; native spe- cies are replaced with consumptive exotics; streams are channelized, piped and buried; wetlands are filled and aquifers depleted. Urban heat islands drive up energy use for cool- ing and trap air pollutants in the city. Downstream areas are flooded and polluted by quick runoff from acres of paved surfaces. Each of these local problems reduces the ability of local ecosystems to accom- plish their ecological functions. Local ecological systems are rapidly losing their ability to produce clean water, air, and food, and to main- tain a rich variety of inhabitants— in short, they are losing the ability to sustain life. Each of these environmental problems is related in some way to the design of cities, to our settle- ment pattern, to our urban spatial structure. Changes in land-use pat- terns take decades, so if our cities are to be ready for mid-21st-century energy and resource scarcities, in- creasing population, and potential extinctions, structural changes must be initiated almost immediately. Human habitat must be restruc- tured so that we live within the lim- its imposed by our life-sustaining ecosystems and follow the organiz- ing principles by which all life flour- ishes. Green City Consciousness To correct the ecological damage caused by today’s gray city, we first have to shift our perceptions. It is impossible to get us out of the ur- ban ecological crisis with the same kind of thinking that created it. We have to learn to think ecologically. We also have to learn to integrate multiple new, and sometimes seem- ingly paradoxical, ways of thinking and perceiving. A sustainable city can be built on three interrelated mental models, each depending on a different set of values for what counts as success. ■ The city as a living system. This way of thinking asks, What form would the city take if we understood it as a manifestation of natural pro- cess? The central insight of the living city concept is that cities and land- scapes are living systems. A city is a