In-between sprawl and fires: long-term forest expansion and settlement dynamics at the wildland–urban interface in Rome, Italy

Abstract

Understanding the intimate dynamics of urban–wildland interfaces in Mediterranean landscapes is particularly challenging because of multiple biophysical factors (dry or arid climate, low-quality soils, poor vegetation cover) determining an increased environmental sensitivity to human pressure. Although dense and compact cities were sprawling rapidly in the most recent decades, many suburban areas in southern Europe still preserve biodiversity-rich habitats, traditional crop mosaics and high-quality relict forest stands. Diachronic forest and settlement maps were analysed over two time intervals (1936–1974 and 1974–2006) representing different socio-economic contexts on a local scale with the aim to assess trends in forest land cover vis à vis urban growth in Rome, central Italy. Forests expanded into agricultural land during the whole time period following cropland abandonment and benefiting from a higher level of land protection from urbanisation, especially during the most recent decades. Although the broadleaved wood dominated the composition of forest fragments at the wildland–urban interface at both the beginning and the end of the study period, coniferous stands showed a slower decrease compared to other wood types, such as those dominated by chestnut or beech. The observed changes in forest composition are the result of a higher disturbance level, possibly triggered by the increase of fire frequency and severity, a higher fragmentation of natural land, intense soil sealing and a larger occurrence of invasive species. Forest diversity increased especially in areas with medium-density settlements, indicating a tendency towards more heterogeneous forest structures at the urban–wildland interface compared to natural landscapes. A long-term monitoring of settlement dynamics and woodland expansion is required to inform a sustainable management of Mediterranean suburban forests.