Landscape Connectivity Modeling in Fragmented Forests

Abstract

Landscape connectivity -- the degree to which the landscape facilitates or impedes animal movement and gene flow among habitat patches -- determines the long-term viability of wildlife populations in fragmented forest landscapes and is a primary target for conservation investment under the EU Biodiversity Strategy 2030 connectivity restoration commitments. This study modelled landscape connectivity for eight forest-dependent vertebrate species (Lynx lynx, Canis lupus, Meles meles, Cervus elaphus, Martes martes, Sciurus vulgaris, Dryocopus martius, Strix uralensis) across a 284,000 km2 boreal-hemiboreal forest landscape in Estonia, Latvia, and Lithuania using three complementary approaches: graph-theoretic network analysis (Conefor 2.6), circuit theory (Circuitscape 5.0), and least-cost path modelling (ArcGIS 10.8), parameterised from GPS telemetry data (284 GPS-collared individuals; 8,420,000 positions) and validated against genetic distance data (RADseq; 18,420 SNPs from 284 individuals in 42 populations across the resistance surface gradient). All three methods identified the same 12 critical connectivity bottlenecks -- infrastructure corridors, urban areas, and agricultural fields intersecting forest patch networks -- but differed in their characterisation of the degree of connectivity bottleneck severity. Circuitscape effective resistance showed the strongest correlation with pairwise genetic distance (Mantel r = 0.74, p < 0.001) for all eight species combined, outperforming least-cost path distance (r = 0.62) and graph-theoretic betweenness (r = 0.48). A Connectivity Priority Index (CPI) integrating all three methods ranked the 12 bottlenecks by urgency, identifying three motorway crossings and two urban expansion zones as requiring immediate wildlife crossing infrastructure investment to maintain effective connectivity for large-bodied species. These results provide a validated, policy-ready connectivity model for the Baltic States under the EU Nature Restoration Law