Environmental degradation caused by urbanization of the Andean piedmonts and related pre-mountain systems can be observed along both Chilean and Argentinean slopes, with a consequent decrease in vegetation productivity, biomass and soil moisture, and generation of heat islands. This leads to degradation of Andean environmental services such as water infiltration and flood control. Fragmentation of vegetation patches and corridors are among the other main impacts on the natural environment. These land cover and land use changes have in turn increased the frequency and magnitude of natural hazards, and the concentration of air, water and soil pollution. Unfortunately, this makes large Latin American cities examples of unsustainable development.

Urban sprawl seems to be directly related to the increase in total imperviousness areas, runoff coefficients, and the interruption of the ecological integrity of the Andean watershed. Significant impacts can also be observed on the social environment, as the recent urbanization process has substantially increased social segregation and socioecological fragmentation in cities. Urban planning and regulations have not explicitly taken account of the environmental effects of urbanization on mountains in Chile. Urban development urgently needs to be strategically assessed in social and environmental terms, and not only as a relevant component of economic growth. The introduction of ecological planning and consideration of environmentally sensitive areas as a relevant form of regulation are proposed here.