Chapter 10 described the conflict between urbanization and sustainable human - ecosystem interaction. Cities depend upon agricultural ecosystems for food and other products. They rely on natural ecosystems for water, wood, recreation and other resources and services. However, despite this dependence, as cities grow they tend to displace or damage agricultural and natural ecosystems, thereby diminishing the environmental support systems upon which they depend. Cities expand over agricultural lands and natural areas; and even where they do not displace agricultural or natural ecosystems, excessive demands for the products of those ecosystems can lead to overexploitation and degradation. Cities also expand indirectly at the expense of natural ecosystems because displacement of agricultural ecosystems and increasing demands for agricultural products can stimulate agricultural expansion far from the city, displacing natural ecosystems there. Modern urban ecosystems can have a strong impact on distant natural ecosystems because their supply zones extend to so many parts of the world.
Why do urban social systems show so little restraint in destroying or damaging the natural and agricultural ecosystems on which they depend? Part of the explanation (as discussed in Chapter 10) is alienation of urban society from nature, particularly if people have no contact with natural or agricultural ecosystems during childhood. The implications for design of urban landscapes are far reaching and profound. Urban landscapes that provide childhood experience with nature may be essential for an ecologically sustainable society. Until recently, virtually all cities contained a landscape mosaic of urban, agricultural and natural ecosystems that provided opportunities for direct contact with nature within walking distance of most people’s homes. Unfortunately, many large cities today have become ‘concrete jungles’ in which this opportunity is no longer available. The result may be a positive feedback loop between an increasingly urbanized society and cities with fewer opportunities for childhood nature experience, creating adults whose lack of emotional connection with nature does not constrain them from damaging their city’s environmental support system. Ensuring that natural ecosystems are retained as part of urban landscapes - or finding ways to restore green areas where they have already been lost - should be high on the agenda of urban communities.