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This study analyzed the patterns and drivers of LULC dynamics in relation to the expansion of large-scale irrigated agriculture in the Central Rift Valley of Ethiopia from 1972 to 2016. Aerial photographs (1972), Landsat images (1980, 2000) and SPOT5 satellite images (2016) were analyzed using GIS tools to reveal LULC changes, and documentation, key informant interviews and focus group discussions were used to ascertain the biophysical and socioeconomic implications and drivers of these dynamics. The study revealed that cultivated and rural settlement land, and urban built-up areas had expanded at the expense of forestland, woodland, shrubland and grassland. While an increase in the production of cash crops had brought some benefits to smallholder farmers, such as access to irrigation and modern agricultural inputs and technologies, the unregulated conversion of natural vegetation to cultivated land resulted in a loss of biodiversity, deforestation, and reduction of pasture and firewood. We identified that significant LULC changes in the study area were caused by intersecting biophysical, economic, institutional, technological and demographic factors, which reinforced each other with varying magnitudes at different moments in time. These changes were underpinned by one key driver, that is, government agricultural policies that promoted investment in commercial agriculture for national and export markets. The study shows that understanding the complex interaction between the contributing factors and drivers of LULC change is crucial to inform decision-making and policies, in particular, by directing responses towards the underlying drivers of change rather than only the proximate causes. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) and total nitrogen (TN) stock are key indicators of soil quality in tropical regions; however, their status is often degraded, especially due to massive deforestation in natural forest areas associated with extensive agricultural land use. The aim of this study was to investigate the dynamics of SOC and TN stock in different land-use systems in the Abobo woreda, Western Ethiopia. To analyze their status, 80 disturbed (composite) and 45 undisturbed soil samples were collected from the top 20 cm of soil in five major land-use types: natural forestlands, grasslands, recently developed commercial farmlands, old commercial farmlands, and small-scale cultivated lands. The results showed that SOC stock varied significantly across the different land-use types, with mean stock ranging from 32.23 Mg·ha−1 in recently developed commercial farmlands to 54.54 Mg·ha−1 in natural forestlands. The mean TN stock ranged from 2.54 Mg·ha−1 in recently developed commercial farmlands to 4.63 Mg·ha−1 in natural forestlands. With natural forestlands as a baseline and the duration ranging in age from 15 to 45 years since land-use conversion, the mean annual absolute rates of change in SOC and TN stock loss were 0.49, 1.49, 0.39, and 0.45 Mg·ha−1·yr−1 and 0.05, 0.14, 0.03, and 0.04 Mg·ha−1·yr−1 for grasslands, recently developed commercial farmlands, old commercial farmlands, and small-scale cultivated lands, respectively. The results of this study revealed that soil disturbance during forestland conversion to tillage enhanced the decomposition rate of organic matter in recently developed commercial farmlands. Nevertheless, after agricultural abandonment and vegetation restoration, the SOC and TN stock capacities were enriched in the old commercial farmlands. It is, therefore, important to effectively restore vegetation and implement sustainable land-use management practices. [ABSTRACT FROM AUTHOR]

Quantifying the recent LULC changes and associated impacts on pastoral and agro-pastoral livelihood systems is important since the effects of LULC changes on environmental resources and human livelihood are not fully understood in our study area. This paper analysed the trend of land use/land cover (LULC) dynamics and its implications on natural resources and human livelihood in the Middle Awash Valley, Central Ethiopian Rift Valley. For the purpose, Landsat imageries of thematic mapper (1987), enhanced thematic mapper (2002) and operational land imager and thermal infrared sensor (2016) were employed and analysed using Remote Sensing and Geographic Information System (GIS) software and techniques, and qualitative data analysis had been performed as well. The results showed that cultivated land expanded at a rate of 2.6% year−1, whereas forestland and grassland shrunk at a rate of 1.2% year−1 and 2.4% year−1, respectively. The invasive Prosopis juliflora has been expanded from 3.7% in 1987 to 37.9% in 2016 at a rate of 1.2% year−1. The introduction of both small- and large-scale commercial irrigation farming and the implementation of villagization programme focused on transforming pastoralists into sedentary lifestyles. Consequently, irrigation farming, launching of villagization, climate variability as in series of droughts, construction of water dam and the rapid expansion of Prosopis juliflora were the major drivers of LULC changes in the study area. Although we found some positive developments such as improvement on infrastructural and social services (e.g. school and domestic water supply), income diversification and ecological benefits from Prosopis juliflora (e.g. saline soil treatment, carbon sequestration and soil erosion control), there were a range of negative impacts resulting from LULC changes in the study area. LULC changes reduced quality of rangeland resources as the ecologically and economically valuable indigenous tree and grass varieties were significantly degraded. As a result, the traditional pastoral livelihood system has been much vulnerable with the LULC dynamism of the study area. Furthermore, the implementation of the villagization programme has brought socioeconomic impacts on the community and challenges on the ecology, e.g. changing productive rangeland to irrigation crop farms. Our research results, thus, suggest the urgent need for relevant policy interventions in support of the pastoral livelihoods and landscapes with the modification in the implementation of villagization as well as irrigation farming programmes and its better management and controlling Prosopis juliflora expansion in the study area. [ABSTRACT FROM AUTHOR]

Soil quality (SQ) dynamics assessment vis-à-vis land use/land cover (LULC) and elevation variations in Ethiopia is desirable as elevation impact on land use is highly pronounced. This study examined SQ indicators dynamics across LULC and elevation variations. For this, surface soil samples (0-20 cm) were collected from the recognized LULC categories of different elevations in Wanka watershed, northwestern Ethiopian highlands. Both disturbed and undisturbed soil samples that were taken from three adjacent LULC (natural forest, grazing and cultivated lands) and elevation (2238-2300, 2400-2600, and 2700-2800) classes analysed for the selected physicochemical SQ indicators. Two-way ANOVA, Tukey's multiple comparison test and SQ deterioration index were computed. The impact of LULC and elevation was found significant on key SQ indicators. In cultivated and grazing lands, soil organic matter (SOM) and soil nutrients like total nitrogen declined significantly (p < 0.01). Conversely, bulk density increased significantly (p < 0.01). The divalent basic cations (Ca2+ and Mg2+), cation exchange capacity and pH significantly (p < 0.01) decreased in upper elevation. Synergetic effect of LULC and elevation variations was found significant (p < 0.01) on SOM, total nitrogen, available phosphorus, water content at field capacity and soil particle distribution (silt and clay). Thus, elevation specific land management strategies that improve these SQ indicators need to be emphasized. [ABSTRACT FROM AUTHOR]

• We have developed a soil quality index to assess the interplay of soil quality. • Soil quality indicators in forestlands and human-managed ecosystems were compared. • Soil quality index is one of the most important indicators of soil health. • Soil quality provides a threshold to prevent ecosystems degradation. Soil quality degrades when natural forests are converted to human-managed ecosystems. Limited empirical evidence of such soil quality changes has been observed in tropical sub-humid ecosystems. This study aimed to analyze the impact of land use change on soil quality dynamics in a tropical sub-humid ecosystem in western Ethiopia. To analyze some impacts, 80 composite soil samples (0–20 cm depth) and 45 undisturbed soil samples (0–7 cm depth) were collected from different land use patterns, including natural forests, grasslands, recently developed commercial lands, old commercial farmlands, and smallholder cultivated farmlands. A one-way analysis of variance (ANOVA) was performed to determine the effect of different land uses on soil quality indicators. The soil quality index (SQI) was used to evaluate the impact of land use on selected soil quality indicators, using the weighted additive SQI method derived from Principal Component Analysis (PCA). Our results showed that certain soil quality indicators, such as soil organic matter, total nitrogen, bulk density, porosity, cation exchange capacity, exchangeable calcium, and magnesium, were significantly degraded when compared to forest soils as a benchmark (at significance levels of P < 0.05, 0.01, and 0.001). Our study concluded that soil organic matter content, pH, field capacity, exchangeable calcium and potassium, available phosphorus, and bulk density could be used as key SQI assessment attributes in tropical sub-humid ecosystems and similar environments. Sustainable land management practices are crucial in enhancing soil quality indicators across different land use systems in tropical sub-humid ecosystems. [ABSTRACT FROM AUTHOR]

Land use/land cover changes in a lake drainage basin reflect changes in the magnitude of the water balance components and rate of sediment deposition in a lake as a reflection of the fundamental linkage between what happens in a lake considered against what is happening in the drainage basin of the lake. The objective of this study was to quantify the spatio-temporal land cover/land use changes across the Lake Hayq closed drainage basin in north-east Ethiopia over a 50-years period, using multitemporal remote sensing and geospatial data. Two historical occasions of aerial photographs (1957 and 1986) and one satellite image (2007) were examined with image analysis tools: Leica Photogrammetric Suite ( LPS 9.2) Project Manager, ArcGIS10.0, and ERDAS EMAGINE 9.2. Seven aerial coverage of land use/land cover categories were identified and mapped for the past three historical times. The results indicated that farmlands/settlements and shrublands/degraded lands increased by 43.1% and 136.9%, at an annual rate of 27.4 and 13.5 ha year−1, respectively, between 1957 and 2007. In contrast, bushlands, grasslands, forestlands and lake surface area were diminished by 68.8%, 62.7%, 90.5% and 7.6%, at a rate of 24.0, 7.6, 6.1 and 3.7 ha year−1, respectively, over the past five decades. The basin had undergone significant transformation in land use/land cover over the past half century, affecting the lake's biophysical stability by accelerating soil erosion in the basin, sediment accumulation, and a reduced quantity and quality of cumulative stream flow into the lake. [ABSTRACT FROM AUTHOR]

Background: Assessment of soil loss rates is crucial to sustainably enhance the benefits of land resources and diminish the adverse impacts of land degradation thereby areas requiring immediate soil erosion management practices can be identified. The study aimed to examine the impacts of land cover dynamics on the spatiotemporal patterns of erosion hotspots. RUSLE factors were produced using GIS and remote sensing techniques.Results: The RUSLE model adapted to Ethiopian conditions was run for 2004 and 2014 where input data layers were overlaid. The results of the model showed clear patterns of changes characterized by gradual shifting of one erosion soil loss severity class into next higher class. There was a net increase in the total soil loss largely under the very high, low and very low soil loss severity classes by 8%, 21% and 9% despite a decline in other severity classes, respectively. It also revealed that more than two-third of the catchment has experienced soil losses rates higher than the tolerable value reported for Ethiopia over which agriculturists should be concerned.Conclusions: Therefore, the observed soil loss rate and sediment yield in the study catchment would lead to further ecological deterioration unless site-specific participatory watershed management practices are employed. [ABSTRACT FROM AUTHOR]