Multi-Scale Synergistic Optimization and Life Cycle Assessment of Blue-Green Infrastructure for Addressing Agricultural Non-Point Source Pollution and Conserving Amphibian Habitats

Abstract

Agricultural intensification has increased non-point source pollution and degraded freshwater habitats essential for amphibian survival and reproduction. Existing control strategies generally focus on local pollution reduction while overlooking habitat connectivity and the life-cycle carbon footprint of blue–green infrastructure. This study examines a typical intensive agricultural watershed in the middle and lower reaches of the Yangtze River and develops an integrated framework combining spatial optimization, carbon accounting, and amphibian habitat conservation. The SWAT model is used to simulate watershed pollution processes and identify critical source areas and transport pathways affecting wetlands, riparian zones, and potential amphibian breeding habitats. The NSGA-II algorithm is then applied to optimize the spatial configuration of blue–green infrastructure across fields, drainage ditches, and river corridors. Life-cycle assessment is employed to quantify pollution-reduction efficiency, carbon footprint, and implementation cost. The optimized configurations reduce total nitrogen and total phosphorus loads by 15.8%–19.1% and 20.5%–23.1%, respectively, while maintaining a comparatively low net carbon footprint. Improved nutrient interception and the restoration of connected wetland and riparian features can reduce environmental pressures on amphibian breeding and dispersal habitats. These findings demonstrate the potential of multi-scale blue–green infrastructure to coordinate agricultural pollution control, low-carbon watershed management, and amphibian habitat conservation.