Planning for Sustainable Land-Use Changes: Indications from an Assessment of Soil Consumption in a Polycentric Region

The present study investigates the relationship between land-use changes and soil capability in a polycentric region of northern Italy over two distinct periods: a dense and compact phase of urban growth observed after the World War II and encompassing three decades (1950s, 1960s, and 1970s) and the low-density dispersed expansion which took place in the area after the late 1970s. By comparing three high-resolution land-use maps for 1954, 1976, and 2008 to a soil-capability map, the study verifies (1) if urban expansion has consumed high-quality soils proportionally more than other soils, and (2) if urban diffusion observed after the late 1970s has consumed more high-quality soils than compact growth did in the aftermath of World War II. The urban areas (increasing by 0.2% per year from 2.5% in 1954 to 14.5% in 2008) consumed proportionally more high-quality than low-quality soils at the expenses of cropland and natural areas. Moreover, dispersed, low-density settlements have developed on land with higher soil capability more frequently than dense urban settlements. The comparison with a monocentric urban region (Rome, Italy) indicates that per-capita land consumption and high-quality soil conversion to impervious land are higher in the investigated northern Italy area. The relevance of soil capability as a target variable for policies mitigating high-quality soil consumption in polycentric regions was discussed.