Long-Term Monitoring and Assessment of Soil Salinity in Türkiye Using Landsat Data (1984-2024)

Soil salinity is one of the most critical environmental stress factors threatening food security and ecosystem functions at the global scale. Since current monitoring methods are generally local-scale and short-term, comprehensive studies revealing long-term salinity dynamics across Türkiye are needed. This research aims to monitor soil salinity and vegetation changes across Türkiye between 1984 and 2024 using Landsat satellite data. In this study, Mann-Kendall and Theil-Sen statistical trend analyses were applied, and the performance of two different masking strategies focusing on agricultural areas (Scenario A) and covering general land cover (Scenario B) in risk detection was compared. Analysis results revealed that during the examined 40-year period, the Salinity Index (SI) showed a decreasing trend while the vegetation index (NDVI) showed an increasing trend across Türkiye, indicating overall improvement. Regionally, improvements associated with drainage works were observed in Central Anatolia and coastal plains, while hotspots carrying secondary salinization risk originating from irrigation projects were detected in the Southeastern Anatolia Region. Additionally, methodological findings demonstrated that the general land cover masking strategy (Scenario B) produced more sensitive results in detecting risk areas compared to the agriculture-focused approach (Scenario A). This study provides policymakers with a science-based decision support tool at the national scale for sustainable land management and climate change adaptation processes.