Landscape planning and defragmentation measures: an assessment of costs and critical issues

Defragmentation, i.e. the systematic action of reconnecting even smaller and more isolated landscape patches, is a major concern for landscape analysists and planners. Landscape fragmentation (LF) can jeopardize both ecosystem continuity and quality. Transport and mobility infrastructures (TMIs) are considered one of the main causes of LF and trigger negative effects, such as death of wild animals killed by vehicular traffic, and decrease of landscape connectivity. The effectiveness of defragmentation actions can be monitored through indices, such as the Infrastructural Fragmentation Index (IFI) and, as a counterpart, the connectivity index (CI). In this paper, we aim at illustrating the effect of defragmentation actions based on the use of wildlife crossing structures (WCSs). WCSs are targeted for the wild boar and ideally located at different linear densities in the fragmented and car accidents very rich landscape unit of Alghero, Sardinia, Italy. Results demonstrate that the higher the WCSs’ density the higher the defragmentation effect and that the average cost of defragmentation increases for scenarios with denser WCSs.