Using graph theory to analyse and assess changes in Mediterranean woodland connectivity

Abstract

Context The Portuguese montado is an agro-silvopastoral system, similar to the Spanish dehesa, known for its cultural, economic and ecological value. Despite its importance, contrasting processes such as land 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 connectivity is vital for many species that, in turn, contribute to the natural processes on which a healthy and sustainable montado relies. Objectives To study the montado connectivity in the recent decades and infer what the changes represent to the short and medium dispersal species regarding habitat availability.Methods The study was conducted in an area delimited by biogeographic boundaries in Southern Portugal where montado is abundant. We used a graph theory 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 to a global connectivity decrement likely to have nega tive implications for montado species. The most affected species are those more dependent on habitat characteristics, such as forest specialist birds, and those with low mobility that have lost great amounts of habitat not only due to montado loss but also due to the increasing fragmentation that makes suitable patches unreachable. Conclusions Given the montado environmental relevance, measures should be taken in order to stop its loss and preserve the core areas that have guaranteed the connectivity over time.