Land-Use/Land-Cover Dynamics in Semi-Arid Catchments and Their Implications for Aquatic Ecosystem Sustainability

Freshwater ecosystems are essential for biodiversity, livelihoods, as well as human well-being, and their condition is strongly influenced by land-use pressures within surrounding catchments. Land-use/land-cover (LULC) change can alter catchment processes and increase pressure on downstream aquatic ecosystems, particularly in semi-arid environments where surface water decline is prevalent. This study assessed the LULC dynamics in the Lake Manyara Catchment (LMC), Tanzania, over the 2016–2026 period using Sentinel-2 Level-2A imagery and supervised Support Vector Machine classification. Five LULC classes were mapped for 2016, 2021, and 2026 using a common catchment boundary, with overall classification accuracies ranging from 87.96% to 89.21%. The results show substantial changes in the composition of the catchment. Developed land increased by 912.38 km2 (86.44%), while agricultural land increased by 325.46 km2 (6.47%). In contrast, forest declined by 390.28 km2 (24.88%), and rangeland by 846.08 km2 (8.42%). These changes in classified land-cover composition indicate increasing human land-use pressure alongside a declining share of semi-natural vegetation, and the observed transformation may increase the potential for altered runoff and erosion, together with sediment and nutrient transfer to downstream waters. Findings highlight the need to manage the LMC as an interconnected land–water system through protecting and restoring semi-natural landscapes, promoting sustainable agriculture and efficient water use, guiding settlement expansion, safeguarding riparian and drainage-connected areas, and integrating satellite and water-quality monitoring to support targeted and adaptive catchment management.