Assessment of the Visual Disaster of Land Degradation and Desertification Using TGSI, SAVI, and NDVI Techniques

Abstract

Land degradation and desertification are a visual disaster that seriously affects ecologically and environmentally and poses socio-economic threats to the global world. There is a tenacious need to develop a reliable and reproducible method to assess it at different scales. In this paper, the semi-arid part of the Kanekal area in Anantapur was taken as the study area. Remote sensing, Landsat TM/ETM+ data on a local scale was used (for the past 29 years from 1990 to 2019) to develop a quantitative method for assessing desertification and land cover changes in the area. In this method, soil-adjusted vegetation index (SAVI) and topsoil grain size index (TGSI) were used for identifying the tendency of the degradation and desertification conditions in the study area. To assess the land cover changes, normalized difference vegetation index (NDVI) was used, and the 29 years’ data is divided into two types, i.e., before 2000 and after 2000. NDVI is categorized into five classes, namely undefined area, unaffected area, vegetation area, degradation area, and desertified areas, and these classes are converted into four levels based on the categories (Levels 1–4). Our analysis reveals that the desertification tendency is continuously increasing every year. From 1990 to 2019, Levels 1–4 (unaffected area) are decreased to 4,051 ha (10.02%), Levels 2–4 (vegetation area) are reduced to 114 ha (0.28%), Levels 3 and 4 (degraded area) are increased to 1,167 ha (2.89%), and Levels 4–4 (desertified land) are increased to 2,770 ha (6.86%). It is also proven that the multitemporal analysis of data from the TGSI, SAVI, and NDVI indexes can provide a sophisticated measure of ecosystem health and variability, and that substantial progress has been made in the respective studies over the past 29 years.