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 responsible 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. MethodsThe 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. ResultsThe results show a loss of montado associated to increasing fragmentation over time. This led to a global connectivity decrement likely to have negative 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.

Fragmentation and Connectivity of Island Forests in Agricultural Mediterranean Environments: A Comparative Study between the Guadalquivir Valley (Spain) and the Apulia Region (Italy)

“…However, an intensive training course should be carried out to obtain optimum results. This software is based on graph structures [45][46][47], whereby, in our study, IFs were nodes and the distance between them connectors. Conefor calculates the PC index (Probability of Connection index), which is the probability that two points randomly located in the landscape are connected in a set composed of n patches and their connections [48,49].…”

Structuring of plant communities across agricultural landscape mosaics: the importance of connectivity and the scale of effect

“…The term 'connectivity' has been used in the field of landscape ecology to describe the movement of an organism through a landscape as a function of distance and landscape structure [1,22,23]. Connectivity is an important concept in community ecology because it affects dispersal among local communities and species interactions within them [24][25][26], and sustains ecosystem function [27,28].…”

Influence of land use changes on landscape connectivity for North China leopard (Panthera pardus japonensis)

“…Graph-theoretic approaches provide a new research idea for powerful leverage on ecological processes concerned with connectivity as defined by dispersal. Graph theory-based models and least-cost path models have gained increasing attention and are widely applied in connectivity modeling, conservation planning, and monitoring of land use changes and their environmental impacts (Minor and Lookingbill, 2010 ;Theobald et al, 2011 ;Piquer-Rodriguez et al, 2012 ;Rubio et al, 2012 ;Devi et al, 2013 ;Wang et al, 2016 ;Sahraoui et al, 2017 ;Liu et al, 2020 ;Machado et al, 2020 ).…”