Research progress on land ecological security under agricultural non-point source pollution constraints and application implications in the hilly watersheds of South China

As ecological environment management becomes more refined, the characterization problem of environmental stress indicators in land ecological security assessments (LESA) of hilly watersheds in South China is becoming increasingly prominent. Existing research relied on single-input indicators to reflect environmental pressure, struggling to reflect the transport characteristics of agricultural non-point source loads (AGNPSL) and the actual state of ecological security in hilly areas. Based on the knowledge graph, empirical cases and other methods, this paper systematically reviewed the literature from 2010 to 2025 on ecological security and agricultural non-point source pollution (AGNPS), analyzed the limitations and evolutionary trends of existing LESA systems, as well as bottlenecks hindering the application of LESA systems in the hilly areas of South China. The existing research primarily focused on the macro-scale assessments of ecosystem services; However, due to the simplification of input indicators, low-resolution of representation features and the spatial heterogeneity of AGNPSL, the macro-scale assessments struggled to meet the needs of refined LESA in hilly areas. The related research had generally evolved through three stages. As existing studies lacked in-depth simulation and analysis on the transport processes of the AGNPSL in hilly areas, LESA systems failed to precisely characterize the environmental load pressure resulting from the AGNPS, thereby hindering the scientific assessment of land ecological risks. Empirical cases demonstrated that the limited accuracy of nitrogen and phosphorus load quantification undermined the reliability of LESA in these hilly areas, thus hindering the precise implementation of management and control measures formulated under this system. In the future, it is necessary to optimize the assessment system, refine the estimation of AGNPSL, and deepen the understanding of the insufficient characterization of traditional single-input indicators and the spatial heterogeneity of environmental pressure indicators, providing a reference for improving the LESA system and ecological risk research.