Ecosystem Service Valuation and Spatial Modeling of Carbon Stock, tree Species Diversity, and Soil Erosion in Bale Mountains Ecoregion, Ethiopia
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Date
2025-01
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Addis Ababa University
Abstract
The Bale Mountains Ecoregion (BMER) has been facing severe deforestation, and land degradation driven by land use and land cover (LULC) changes that alarmingly impact its ecosystem conditions. Despite the severity of these challenges, there has been inadequate scientific knowledge on how these drivers affect the spatial distribution of ecosystem attributes and ecosystem service values (ESVs). This PhD research has aimed to contribute to address the knowledge gap, employing extensive ground-based geospatial data collection, remotely sensed satellite imagery, and advanced spatial modeling to explore the condition of the BMER ecosystem using various indicators of ecosystem attributes. Landsat images of the years 2010, 2015, and 2022 were acquired, and standard image pre-processing and analysis techniques were applied to generate LULC data and examine ecosystem dynamics. The LULC was used to conduct ecosystem service valuation by applying adopted coefficients for each service to the corresponding ecosystem areas at the BMER. At the same scale, soil loss was estimated and mapped for 2010 and 2022 using the Revised Universal Soil Loss Equation (RUSLE) and the Geographic Information System (GIS). Additionally, 236 sample plots were randomly selected in the forest of BMER to map the spatial distribution of Aboveground Carbon Density (ACD) and species diversity using kriging techniques.The maps of species indices were classified into six categories and related with a deforesation area map occurred during 2010 and 2022 to quanitify impacts of an area of deforesation on different classes of forest attributes using Zonal stitistics in ArcGIS map. Zooming into detail, additional forest data were collected from 1,122 sample plots in the Harana Forest to model the impacts of biophysical factors on ACD and the abundance of dominant tree species, applying Random Forest (RF), Artificial Neural Network (ANN), and Generalized Linear Model (GLM) approaches. The findings showed a significant decline in the ESV of BMER, from US$ 103 billion in 2010 to US$ 92.5 billion in 2022. Forest ecosystems showed a marked decrease in value, from US$ 94.5 billion to US$ 82.2 billion, while water ecosystem services declined from US$ 38.6 billion to US$ 35.4 billion. Climate regulation services experienced a reduction of US$ 76.4 million, whereas farmland ESV increased from US$ 4.81 billion to US$ 7.12 billion over the same period. Soil loss also worsened, with mean soil loss increasing from 0–306 t/ha/yr in 2010 to 0–391 t/ha/yr in 2022. The total soil loss increased from 4.5 million tons to 7.5 million tons between 2010 and 2022. Farmland was the most affected, accounting for 56.06% of total soil loss in 2010 and 68.9% in 2022. The ACD between 63 to 118 t/ha accounted for 54% of the total forest area, while a maximum of ACD of 282 and 336 t/ha accounted for only 0.3%. Species richness was unevenly distributed, with the highest class (24.00–28.29) covering 877 ha (0.1%) of the total area, while the lowest class (2.55–6.84) occupied 32%. The deforestation of 10,356 ha resulted in losses of species richness in a class of (6.84 to 11.13). The deforestation of 7,746 ha caused a loss of the Shannon-Weiner diversity indices (1.36 to 1.67). Biotic factors primarily influenced the spatial distribution of ACD in the Harana forest. The abundance of dominant tree species was influenced by elevation, temperature, rainfall, clay content, and potassium levels. In conclusion, this research provides a spatially explicit, quantitative scientific understanding of the ecosystem conditions of BMER. These findings provide critical empirical evidence to inform conservation interventions and strategies for sustainable ecosystem management of the BMER.
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Ecosystem Service Valuation, Spatial Modeling, Carbon Stock, tree Species Diversity, Soil Erosion, Bale Mountains Ecoregion, Ethiopia