Urban form, structure and dynamics
Despite being relatively well-planned and therefore spatially organised from a human perspective, urban environments are ecologically complex and heterogeneous in structure. This complexity depends upon the spatial scale considered, so that at the broadest scales particular typologies or patterns of urban form are observable, with implications for the ecology of the urban region. At ﬁner spatial scales, patterns or trends in the arrangement of biotic and abiotic components can be observed (such as the density of buildings, gardens or street trees), again with related inﬂuences on urban ecology. Furthermore, urban environments are by nature dynamic, with relatively frequent changes in their physical fabric (e.g. construction and organisation of the built environment) and social organisation (e.g. as groups broadly deﬁned by socio-economic or cultural characteristics shift location over time). Consequently, this chapter focuses on the different forms and structures of urban areas at different spatial scales, from the broad spatial layout and organisation of entire regions (including the formation of urban typologies), to the spatial organisation of landscape components within the urban complex. The biophysical dynamics of urban environments at each scale are also brieﬂy discussed. Although this topic is vast and could form the basis for an entire book, and as such one chapter cannot provide comprehensive coverage, a broad overview of spatial organisation in urban regions is essential for developing an understanding of urban ecosystems and their ecology.