Configurational Fragility of Forest Landscapes Under Multiple Anthropic Uses

The conversion of native vegetation to anthropogenic land uses and landscape fragmentation are primary drivers of biodiversity loss and ecosystem services decline in tropical watersheds. Understanding how land use shapes the spatial configuration of forest fragments is essential to inform conservation and restoration strategies. We evaluated the configurational fragility of forest remains in the Lower São Francisco River Watershed, Brazil, combining structural metrics (area, core area and shape index) with land use and land cover (LULC). Fragility levels were defined through hierarchical classification and their relationship with LULC was tested using distance-based redundancy analysis (db-RDA). A principal component analysis (PCA) first summarized LULC variation. The watershed is dominated by anthropogenic matrices, with agriculture and pasture occupying 66.9% of the area, mainly pasture (57.7%). This resulted in 37,022 highly reduced and discontinuous forest fragments, of which 72.2% exhibited high configurational fragility. Savanna formation, the most representative native vegetation, had 96.1% of its patches within intermediate to high fragility levels. The PCA revealed three dominant gradients: herbaceous formations, wooded sandbank vegetation and wetlands (PC1), contrast between savanna formations and pasture (PC2), and heterogeneity of forests, forest plantation and mosaic of uses (PC3). db-RDA confirmed this pattern (adjusted R ² = 0.362), with CAP1 explaining 92.2% of the constrained variation, demonstrating a strong opposition between natural environments and anthropogenic land uses. This study shows that configurational fragility is strongly driven by anthropogenic LULC, revealing that landscapes with the same forest cover may differ in fragility depending on the spatial organization of the remnants. In the area analyzed, sublevels High III and Intermediate I predominated, where small fragments dominated by edges coexist with larger and irregular patches, with occasional occurrences of Low III. As a management guideline, it is recommended to protect strategic remnants, intervene in intermediate areas, and restore zones of high fragility. Future studies should integrate these sublevels with functional indicators and temporal dynamics.