Spatiotemporal land use and cover changes across agroecologies and slope gradients using geospatial technologies in Zoa watershed, Southwest Ethiopia

Abstract

Environmental phenomena are always changing elsewhere in various scales depending on both natural phenomenon and human interference. Land use/over change (LULC) is related to site specific factors such as inappropriate land use planning and the expansion of traditional agricultural practices in steep gradients have led to soil erosion and consequent ecological changes. Thus, it is crucial to determine the trend, pattern, and drivers of land use/land cover dynamics for sustainable natural resource management in Ethiopia. Therefore, we evaluated the spatio-temporal LULC dynamics in different agroeclogies and slope gradients, and their drivers between 1985 and 2021 in the Zoa watershed of Omo-Gibe basin, Southwest Ethiopia. Landsat imageries, focus group discussants, key informants, and field observations were used as source of data to analyze the spatio-temporal LULC trajectories and their drivers. With total accuracies ranging from 87.55% to 91.14%, supervised image classification using the Maximum Likelihood classifier technique was used to categorize five key LULC classes: bareland, farmland, forestland, grassland, and shrubland. The results revealed that shrubland (41.87%) had the largest share in 1985, but later declined to 23.98% in 2000, and 12.6% in 2021. Grassland has declined as well, from 17.15% in 1985 to 2.09% in 2021. In contrast, farmland increased at the fastest rate, from 29.09% in 1985 to 71.12% in 2021. The proportion of farmland exhibited an increasing trend in all agro-ecologies, while forestland has increased only in highland agro-ecologies. Between 1985 and 2021, an extensive area of shrubland and grassland were converted into farmland with a conversation rate of 1.05% and 0.58% per annum, respectively. The expansion of farmland was observed towards moderately and steep rolling slopes which might exacerbate soil degradation. This is due to rapid population increase and ongoing demand for agricultural land. The result of key informant interviews and focus group discussions also revealed that expansion of farmland and settlement are the major drivers of LULC dynamics due to rapid human population growth. Therefore, the regional government and various stakeholders should work on redesigning effective management strategies through appropriate land use planning to address the adverse effects of LULC dynamics.