Spatially targeted nitrogen management in a coastal megaregion: A hybrid framework from food production-consumption to source-sink relationships

Abstract

Sustainable nitrogen (N) management is urgently needed in coastal megaregions, yet a systematic understanding of the spatial drivers of N losses, linking metabolic inefficiencies (“sources”) to landscape-driven transport (“sinks”), remains lacking. We address this gap by integrating Substance Flow Analysis, Minimum Cumulative Resistance modeling, and convergence analysis to quantify N flows and efficiency across nine cities in the Shanghai Metropolitan Area (2011-2020). Results revealed that nitrogen losses occurred predominantly through atmospheric dispersion (45.6%) and surface water (39.8%), with high spatial variability linked to landscape resistance and subsystem metabolism. Significant spatial convergence (a narrowing of efficiency gaps among cities) was observed in crop (−0.271, p < 0.05, t_life = 19.736) and aquaculture (−0.376, p < 0.01, t_life = 13.228) nitrogen use efficiency, whereas livestock and recycling systems exhibited divergent trends (a widening of gaps), reflecting uneven regional coordination. This hybrid framework uniquely links metabolic performance to landscape-mediated risk patterns, diagnosing why hotspots emerge. This provides a systemic basis for spatially differentiated management, underscoring that sustainable N governance in coastal megaregions requires concurrently optimizing system metabolism and ecological connectivity.