Effective mesh size as an indicator of connectivity: a comparative approach

Landscape fragmentation (LF) is a process widely caused by road infrastructure and urbanised areas. LF consists in dividing a natural environment in different fragments separated from each other and in reducing the original land surface. The most obvious effects are: the isolation of animal and plant species, the reduction of biodiversity and loss of connectivity between natural areas. In the literature, there are a number of indicators available for quantifying LF. In this work, we assess LF in four case study units, two located in Sardinia (Italy), and two in Wales (the UK). We apply an effective mesh size indicator, which expresses the probability that two randomly chosen points are then connectable, without roads or urban barriers impeding the connectivity. This index can provide answers on the degree of connectivity of a habitat, taking into account intra and inter patch movement. We consider as target species the hedgehog, which is widespread mainly in urban and suburban contexts and suffers from the negative effects of LF. We will assume five possible connection scenarios between isolated patches through the application of various buffers between 50 and 2000 m. The results of this research show that the LF (mesh size) is lower in the Limbara region of Sardinia and in Northeast Wales and provide useful indications to environmental and landscape planners and decision-makers involved in defragmentation policies.