Bi-temporal assessment of vegetation-cover change using Landsat modified soil adjusted vegetation index (1984–2022): The Oued Rdat Basin, Morocco

Abstract

Vegetation cover is an important indicator of ecosystem condition and environmental sustainability, particularly in semi-arid regions affected by climatic variability and anthropogenic pressures. This study assesses vegetation-cover differences in the Oued Rdat Basin, northwestern Morocco, between 1984 and 2022 using Landsat imagery, the modified soil adjusted vegetation index (MSAVI), and Geographic Information Systems. Two Landsat scenes acquired in July 1984 and July 2022 were processed and compared using a post-classification approach to identify net spatial changes in vegetation conditions. The 2022 MSAVI classification was independently evaluated using 100 validation points derived from high-resolution Google Earth Pro imagery, yielding an overall accuracy of 85.0% and a Kappa coefficient of 0.80. The results indicate that vegetated surfaces decreased from approximately 62% of the basin area in 1984 to 40% in 2022, representing a net reduction of 22 percentage points. Conversely, bare or sparsely vegetated surfaces increased from approximately 38% to 60%. Vegetation loss was concentrated mainly in the central and downstream sectors, whereas localized recovery and persistent vegetation were observed in some upstream and mountainous areas. These patterns may reflect the combined influence of climatic vari - ability, land-use change, and other anthropogenic pressures; however, their relative contributions were not quantitatively assessed. Because the analysis is based on two observation dates, the results represent net bi-temporal differences rather than a continuous vegetation trajectory. The findings demonstrate the usefulness of combining MSAVI and GIS for identifying vegetation-loss areas and supporting watershed management, ecosystem restora - tion, and environmental planning in semi-arid environments.