Abstract
Mapping and quantifying land degradation status is important for identifying vulnerable areas and to design sustainable landscape management. This study maps and quantifies land degradation status in the north Gojjam sub-basin of the Upper Blue Nile River (Abbay) using GIS and remote sensing integrated with multicriteria analysis (MCA). This is accomplished using a combination of biological, physical, and chemical land degradation indicators to generate a comprehensive land degradation assessment. All indicators were standardized and weighted using analytical hierarchy and pairwise comparison techniques. About 45.3% of the sub-basin was found to experience high to very high soil loss risk, with an average soil loss of 46 t ha−1yr−1. More than half of the sub-basin was found to experience moderate to high level of biological degradation (low vegetation status and low soil organic matter level). In total, 80.2% of the area is characterized as having a moderate level of physical land degradation. Similarly, the status of chemical degradation for about 55.8% and 39% of the sub-basin was grouped as low and moderate, respectively. The combined spatial MCA of biological, chemical, and physical land degradation indicators showed that about 1.14%, 32%, 35.4%, and 30.5% of the sub-basin exhibited very low, low, moderate, and high degradation level, respectively. This study has concluded that soil erosion and high level of biological degradation are the most important indicators of land degradation in the north Gojjam sub-basin. Hence, the study suggests the need for integrated land management practices to reduce land degradation, enhance the soil organic matter content, and increase the vegetation cover in the sub-basin.
Highlights
Introduction iationsLand is a critical natural resource for human survival and the base for all terrestrial ecosystem services
The criteria were weighted through the pairwise comparison of individual land degradation indicators which derived from raster data following analytical hierarchy process (AHP) approach
We considered only soil and stone bunds conservation structures because most other Sustainable land management (SLM) options observed in the sub-basin were not well-designed and not widely used
Summary
The total population of the sub-basin and surrounding villages at the time of the study was 3,565,892 [40], settled in scattered areas. According to the Ethiopian National Metrological Agency, the average maximum and minimum temperature of the sub-basin varies from 24.6–28.1 ◦ C and 11.0–14.5 ◦ C, respectively, and the mean annual temperature is 19.4 ◦ C [42]. Meteorological records from stations within the sub-basin and in the surrounding area indicated that the mean annual rainfall (1986–2017) is 1334.48 mm with a minimum of 810 mm and a maximum of 1815 mm [42]. Unreliable rainfed mixed crop and livestock production agriculture is the primary source of livelihood for the majority of the population in the sub-basin. Sheep, goats, horses, donkeys, mules, and poultry
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