The role of protected areas in preserving habitat and functional connectivity for mobile flying vertebrates: the common noctule bat (Nyctalus noctula) in Tuscany (Italy) as a case study

Preserving species within protected areas (PAs) does not guarantee adequate levels of protection if not coupled with conservation of functional connectivity for a target species. We propose an analytical framework to assess the effectiveness of PAs in preserving habitat and functional connectivity for mobile vertebrates. We implemented it in central Italy by using as a case study a bat species (common noctule, Nyctalus noctula) to: (i) determine suitable areas by means of Species Distribution Models (SDMs); (ii) identify potential commuting corridors through a functional connectivity analysis; (iii) develop a new tool to rank corridors according to their functional irreplaceability; (iv) implement a gap analysis on both suitable areas and functional corridors; and (v) propose management recommendations for the conservation of N. noctula. The SDM output and a set of proxies of commuting routes were used to build a resistance layer for the connectivity analysis. The resulting functional corridors were ranked according to their isolation (distance to other corridors and to suitable areas) to obtain an irreplaceability index, with isolated corridors scoring high values. The PA effectiveness assessed by overlapping the PA map with the SDM and the ranked functional corridors highlighted that PAs cover just a small portion of suitable sites (20.3%) and functional corridors for the species (20.8%). The irreplaceability index allowed us to identify those areas inside and outside the PAs that critical for persistence of the species in question require immediate protection regimes. The approach we present could be easily extended to other taxa and offers sound insight on how to promote the conservation at landscape scale.