The Urban Ecosystem

Cities are complex ecological systems dominated by humans. The human elements make them different from natural ecosystems in many ways. From an ecological perspective, urban ecosystems differ from natural ones in several respects: in their climate, soil, hydrology, species composition, population dynamics, and flows of energy and matter (Rebele 1994, Collins et al. 2000, Pickett et al. 2001). Humans create distinctive ecological patterns, processes, disturbances, and subtle effects (McDonnel et al. 1993). Planners must consider all these factors in order to effectively plan cities that will be ecologically resilient. Managing these systems requires an understanding of the mechanisms that link human and ecological processes and control their dynamics and evolution. Because change is an inherent property of ecological systems, the capacity of urban ecosystems to respond and adapt to these changes is an important factor in making cities sustainable over the long term (Alberti and Marzluff 2004).