Assessment of Vegetation Cover Quality and Health Using Spectral Drought Indices

Abstract

This study aims to assess the quality and health of vegetation cover in Thi-Qar Governorate using spectral drought indices (NDVI, VCI, TCI, and VHI) derived from satellite imagery for the period 1990–2023. The objective is to diagnose the dynamics of vegetation condition and to monitor the intensity of water and thermal stress in arid and semi-arid environments. Remote sensing data were analyzed using Landsat satellite images (TM, ETM+, and OLI) within a Geographic Information Systems (GIS) environment to identify the spatial and temporal changes in the spectral indices.The results showed that vegetation indices (NDVI) indicated the dominance of very severe and severe degradation levels over large areas, reaching a peak in 1990 with an area of 98.77 km² (99.64%), reflecting the region’s exposure to recurrent drought events and weak vegetation regeneration. The Vegetation Condition Index (VCI) revealed the prevalence of very severe drought classes in most years, reaching 54.66% in 1990 and 92.62% in 2018. Meanwhile, the Thermal Condition Index (TCI) showed a marked increase in thermal stress, peaking in the years 1990, 1996, and 2023, with an affected area exceeding 60 km² (>60%) of the total study area. The Vegetation Health Index (VHI) reflected clear environmental degradation, as the area classified as very severe drought reached 59.34 km² (59.86%) in 2023.These findings indicate that Thi-Qar Governorate suffers from high environmental fragility and extreme sensitivity to climatic variations. The dynamics of vegetation cover are directly affected by thermal and moisture drought factors and by fluctuations in rainfall. The study recommends the implementation of rehabilitation and integrated management programs based on increasing permanent vegetation cover, rainwater harvesting, and improving soil properties to limit vegetation degradation and enhance its sustainability.