GIS-based assessment of land degradation vulnerability and environmental indices as ecological indicators in Western Agro-climatic zone of Tamil Nadu, India

Land degradation is a critical global issue that affects soil fertility, food production, and biomass, driven by climate change and human activities. This study evaluates land degradation (LD) vulnerability across various land use and land cover (LULC) types in the Western Agroclimatic Zone of Theni district, Tamil Nadu, India. The GIS-based land degradation vulnerability index (LDVI) is calculated to identify site-specific degradation rates by combining four indicators (QI): Soil Quality Index (SQI), Climate Quality Index (CQI), Vegetation Quality Index (VQI), and Land Management Quality Index (MQI), derived from various geo-environmental and climatic variables. The LDVI map classifies the area into four categories: (i) non- affected zones (N), (ii) potential vegetative cover (P) with LDVI < 1. 22, (iii) fragile zones (F 1, F 2, and F 3) with LDVI values from 1. 23 to 1. 1.37, and (iv) critical zones (C 1 and C 2) with LDVI values between 1. 38 and 1. 53. A critical zone (C 3) with LDVI > 1.53. 53 indicates a severe land degradation risk, covering 3.68% of the total area. About 25. Approximately 38% of the region is affected by severe land degradation, primarily on pediplains, barrens, and fallows, resulting from soil erosion, salinity intrusion, nutrient loss, and inadequate land management. Meanwhile, 44. 38% falls within fragile categories, primarily on alluvial plains with red loamy soils. Conversely, 26. 3% of the area is classified as lower risk zones, such as forests, plantations, and irrigated lands, which benefit from soil fertility retention and effective management. The geographic correlation analysis reveals a strong positive relationship with VQI and MQI, with ‘r’ values of 0.835 and 0.831, respectively, indicating a risk to cultivable lands. Significantly, Pearson’s correlation confirms a strong positive relationship between LDVI and SQI and VQI, with coefficient values of 0.99 and 0.84, respectively, indicating that changes in soil properties and vegetation (NDVI) have a direct influence on land degradation across various regions. These findings provide a site-specific land degradation rate and its spatial relationship to quality indicators, emphasizing the importance of land-water-soil management for mitigation. Although the LDVI map reveals a spatial pattern of land degradation at a 30 m x 30 m pixel scale, limited by the resolution and temporal scale of the input datasets, future work could improve the LDVI by incorporating higher-resolution input data and field observations. This research directly supports UN-SDG 2 - Zero Hunger (sustainable agriculture and food security), and SDG 13 - Climate Action (climate resilience and adaptation).