One of the major consequences of expansive urban growth is the degradation and loss of productive agricultural land and agroecosystem functions. Four landscape metrics—Percentage of Land (PLAND), Mean Parcel Size (MPS), Parcel Density (PD), and Modified Simpson’s Diversity Index (MSDI)—were calculated for 1 km × 1 km cells along three 50 km-long transects that extend out from the Adelaide CBD, in order to analyze variations in landscape structures. Each transect has different land uses beyond the built-up area, and they differ in topography, soils, and rates of urban expansion. Our new findings are that zones of agricultural land fragmentation can be identified by the relationships between MPS and PD, that these occur in areas where PD ranges from 7 and 35, and that these occur regardless of distance along the transect, land use, topography, soils, or rates of urban growth. This suggests a geometry of fragmentation that may be consistent, and indicates that quantification of both land use and land-use change in zones of fragmentation is potentially important in planning.

The loss of agricultural land at urban fringes is often monitored but rarely analysed under different scenarios of urban sprawl. This study adopts a multi-criteria spatially-explicit approach to investigate agricultural land vulnerability to urban sprawl under opposing policy directions in the Adelaide metropolitan area. Six land-use change parameters representing the socio-economic and land-use planning effects were analysed under the scenarios of; Business-As-Usual (BAU), Accelerated Economic Development (EDS) and a high Environmental Protection Scenario (EPS). The study shows higher agricultural land vulnerabilities in EDS and BAU scenarios that extends into rural areas displaying a leap-frog effect, which confirms the need to sacrifice farm land uses to maintain land supply for urban development. The LGA-based results enable transfer of farmland vulnerability knowledge into practice by identifying high priority areas for land management interventions and by specifying the types of agricultural land to be strategically managed in these urban fringe landscapes.