Using graph theory to analyse and assess changesin Mediterranean woodland connectivity

Abstract

The Portuguese montado is an agro-sil-vopastoral system, similar to the Spanish dehesa,known for its cultural, economic and ecological value.Despite its importance, contrasting processes such asland abandonment and land use intensification,together with several other factors, have been respon-sible for montado degradation in the last decades.Biodiversitywise, assuring high levels of connectivityis vital for many species that, in turn, contribute to thenatural processes on which a healthy and sustainablemontado relies.Objectives To study the montado connectivity in therecent decades and infer what the changes represent tothe short and medium dispersal species regardinghabitat availability. The study was conducted in an areadelimited by biogeographic boundaries in SouthernPortugal where montado is abundant. We used a graphtheory based approach and montado maps of 1984,1999 and 2014 derived from remote sensing.Results The results show a loss of montado associ-ated to increasing fragmentation over time. This led toa global connectivity decrement likely to have nega-tive implications for montado species. The mostaffected species are those more dependent on habitatcharacteristics, such as forest specialist birds, andthose with low mobility that have lost great amounts ofhabitat not only due to montado loss but also due to theincreasing fragmentation that makes suitable patches unreachable.