From Land to Rivers: Exploring Landscape Connectivity and Nutrient Transport in River Basins

Landscape spatial patterns are critical drivers of ecological processes, including nutrient cycling from terrestrial to aquatic systems, which ultimately modulate microorganism biodiversity. The emergence of robust spatial analysis tools now makes it possible to disentangle these complex relationships through controlled scenario generation. This study assesses the influence of land use and land cover (LULC) configuration on the export of total nitrogen (TN) and total phosphorus (TP) in an anthropogenically impacted river basin. We characterized the baseline landscape and generated synthetic LULC scenarios using the rflsgen (version 1.2.2) R package. Landscape metrics were calculated with landscape metrics, and nutrient export was modeled with the Nutrient Delivery Ratio (NDR) module of InVEST. The results demonstrate that spatial arrangement of the landscape is a key determinant of nutrient dynamics. Agriculture and urban areas have the greatest impact on nutrient export. Nutrient delivery is maximized when these LULC classes are configured in large, compact, and simply-shaped patches with high connectivity, which facilitates efficient hydrological transport. Conversely, fragmented natural grasslands and aggregated forests with regular shapes are associated with lower nutrient export, highlighting their role as nutrient sinks. This integrative methodology provides a novel framework for reproducible spatial experiments, offering evidence-based insights for land-use planning aiming to mitigate eutrophication and enhance ecosystem health.