Within the Chilean region with a mediterranean climate sensu stricto (Aschmann, 1973; di Castri, 1973) there are two main types of landscapes: the low flatlands and the lower mountainous areas (Fuentes, 1988). The flatland areas are mainly found along the coast, in major river valleys, and constitute the Intermediate Depression (Figure 4.1). The second type of landscape, the low mountainous, occurs as the coastal ranges and the lower part of the Andes. Above these two landscapes are the desolate high Andean landscapes in which winter temperature is low and precipitation high. These high Andean landscapes are very important for land use in the areas with mediterranean climate because they serve as snow accumulators during the winter and supply water during the nonwinter seasons for agriculture and the urban centres of the lowland areas (Weischet, 1970). It is this high altitude water reservoir, all along central Chile, that allowed the lowland flatter areas to be developed and transformed into various types of cultivated fields.

The transformation of the low flatlands has been radical, to the extent that the original vegetation is frequently unknown and still a topic of some debate (see Oberdorfer, 1960; Mann, 1968; Fuentes et al., 1989, 1990). These lowlands are undoubtedly the most ‘domesticated’ or ‘artificial’ areas, where introduced plants and animals are most frequent and native species scarcest. These are also the areas where the overwhelming bulk of the Chilean human population lives and has lived since pre-Columbian times (García Vidal, 1982).