Landscape Signatures

Abstract

Urban landscapes exhibit some fundamental features of complex systems. They are open, nonlinear, and highly unpredictable (Hartvigsen et al. 1998, Levin 1998, Portugali 2000, Folke et al. 2002, Gunderson and Holling 2002). Furthermore, they are highly heterogeneous, spatially nested, and hierarchically structured (Wu and David 2002). Disturbances are frequent— an intrinsic characteristic of such systems (Cook 2000). Many factors cause these disturbances, which can follow multiple pathways as they develop and depend greatly on historical context; that is, they are path-dependent (Allen and Sanglier 1978, 1979, McDonnell and Pickett 1993). As other complex systems, urban landscapes are made up of many interacting heterogeneous components, and these interactions lead to emergent patterns that cannot be predicted from an understanding of the behavior of the individual parts. The evolution of such landscapes is in itself an emergent property. Furthermore, uncertainty is important, since any change that departs from past trends can affect the trajectories of landscape dynamics. What makes urban landscapes particularly complex is that they are hybrid phenomena emerging from interactions between human agents and ecological processes (Forman 1995, Spirn 1998, Bell 1999, Wu and David 2002, Alberti et al. 2003, Cadenasso et al. 2006). Consider, for example, the patterns of natural and built elements in an urbanizing watershed. They reflect simultaneously pre-existent biophysical factors, such as land cover, geomorphology, hydrology, climate, and natural disturbance regimes. At the same time, they reflect the decisions regarding land and infrastructure development of multiple human agents (both individuals and organizations) who interact in economic markets and public institutions (e.g., governments). Both the emerging natural and built elements of the landscape, in turn, affect human and ecosystem functions.