Assessing landscape fragmentation in Sardinia (Italy): the barrier effect

Transport and mobility infrastructures (TMIs) are well-known causes of landscape fragmentation (LF). TMIs have negative effects on ecosystem integrity, flora, and fauna. Several metrics able to measure LF are discussed in international scientific literature, but few indices have been proposed to quantify LF due to TMIs. In recent years, some authors have proposed -and applied in different contexts- the Infrastructural Fragmentation Index (IFI) for measuring such a type of LF. The IFI does not take into account the so-called ‘barrier effect’, namely how wild fauna perceives the TMIs. We aim to propose and apply a modified IFI-based index, the Barrier Fragmentation Index (BFI), to consider the barrier effect in measuring LF as perceived by given target species. Furthermore, we aim to measure the probability of connectivity (PC) between fragments (or patches). The PC measures the probability that two animals, located in two different adjoining patches, are able to reach each other. We calculate BFI and PC for three landscape units of Sardinia, Italy, by means of a GIS including data on roads and railways, and discontinuities, such as bridges and tunnel, and ortho-photos. We select the hedgehog (Erinaceus europaeus italicus) as target species. We verify that BFI values are lower than the corresponding IFI figures and that the two indices display similar variations in time. In areas with high values of BFI, mitigation strategies should be planned to reconnect isolated fragments.