This chapter is about some basic geometric considerations and scaling laws in the spatial structure of habitats and (meta)populations.
Conservation of a valuable species, or conversely, eradication of an invasive species can be significantly helped by mapping its potential habitats. It is not easy, however, to measure the value of a habitat patch for a population or subpopulation. Not only the quality, but also the size and shape of the patch can influence birth, death, migration or dispersal (Forman, 1995; Wiens, 1997; chapter 8 in Turner, Gardner & O'Neill, 2001). The wider context, patch-to-patch neighborhood is another matter of consideration, because it can directly influence the movement of individuals (cf. borderline penetrability; Wiens, 1997) or survival and reproduction (cf. edge effects, ecotone effects; chapter 3 in Forman, 1995; Milne et al., 1996; Harrison & Bruna, 1999). Spatial patterns on larger, regional scales are not negligible either. For example, habitat fragmentation is often a serious threat to survival (Fahrig, 2003). Many species require multiple patch types for completing the life cycle, or performing different activities (e.g. feeding and breeding). In this case, the proximity of different patch types in the patchwork also matters. Finally, the patches are rarely constant: they can shrink, expand, or shift; new patches can appear and old ones disappear. The changes can seriously challenge survival (Keymer et al., 2000; see also Wiens, 1997 about habitat tracking).