Integrated Hydro-Climatic Agricultural Land Suitability Assessment Using Multi-Criteria Decision Analysis and Long-Term Satellite Observations

Agricultural land suitability assessment is critical for climate adaptation planning in semi-arid tropical regions to capture temporal hydro-climatic dynamics. This study integrated nine biophysical factors; aridity index, rainfall, rainfall variability, root-zone available water, soil organic carbon, soil pH, soil texture, and terrain slope within an FAO-based Multi-Criteria Decision Analysis (MCDA) framework to assess agricultural suitability across Tamil Nadu's cropland over 2002-2024. We derived hydro-climatic variables from CHIRPS v2.0 precipitation and MODIS evapotranspiration data, soil properties from SoilGrids250m v2.0, and validated composite suitability scores against 23-year MODIS NDVI observations. Results revealed that 49.13% of croplands were classified as marginally suitable (S3) and 50.76% as moderately suitable (S2), with virtually no highly huitable (S1) areas due to chronic atmospheric moisture deficit (mean aridity index: 0.61). Aridity emerged as the dominant constraint (mean score: 1.83/5.0), followed by depleted soil organic carbon (2.99/5.0) and limited root-zone water capacity (2.77/5.0). Temporal analysis demonstrated positive trends in rainfall (+4.64 mm yr⁻¹) and NDVI (+0.0030 yr⁻¹), with 0.82 Mha transitioning from S3 to S2 between 2013-2018 and 2019-2024. Independent validation yielded strong spatial correlation (r = 0.75, p < 0.001) between suitability scores and observed productivity. These findings provide spatially explicit evidence for prioritizing soil carbon restoration, drought-resilient cropping systems, and targeted irrigation investments to enhance agricultural sustainability under intensifying climate variability across semi-arid South Asia.