Dissertations / Theses on the topic 'Rift valley Ethiopia'

Technical complexities and the high cost of satellite images have hindered the adoption of remote sensing technology and tools for nature conservation works in Ethiopia as in many developing countries. The terrestrial and aquatic ecosystems in Abijjata Shala Lakes National Park (ASLNP) and the Important Bird Areas (IBAs) around the park are considered to be one of the most important home ranges for birds. However, little is known about the effect of land use/land cover (LULC) dynamics, due to lack of technical know how and logistical problems. However, it has been shown in this study that sophisticated image management works are not always relevant. Instead a simple method of utilizing the thermal band has been demonstrated. A new approach of long-term dynamics analysis method has also been suggested. A successful classification of images was achieved after such simple enhancement tests. It has been discovered that, there were more active LULC change processes in the area in the first study period (1973 to 1986) than during the second study period (1986-2000). In the first period nearly half of the landscape underwent land cover change processes with more than 26% of the entire landscape experiencing forest or land degradation. In the second period the extent of the change process was limited to only 1/3 of the total area with a smaller amount of degradation processes than before. During the entire study period, agriculture was responsible for the loss of more than 4/5 of the total terrestrial productive ecosystem. More than 37.6% of the total park area has been experiencing this loss for the past 3 decades. Only 1/5 of this area has a chance to revive, the remaining has undergone a permanent degradation. Lake Abijjata lost half of its size during the past 30 years. In the Zeway-Awassa basin 750 km², 2428km² and 3575km² of terrestrial lands and water bodies are within a distance of 10km, 20km and 30km from IBAs respectively. There are ecologically important areas where two or more IBAs overlap. In areas where more than two to five IBAs overlap, up to 85km² of areas have been recently degraded. High livestock density is one of the reasons for degradation. Using a monthly MODIS data from 2000-2005 and a series of interpolation techniques, the productivity of the area as well as the standing biomass were estimated. Moreover, a new method of spatially accurate livestock density assessment was developed in this study. Only 0.3% of the park area is found to be suitable for productive livestock development but nearly all inhabitants think the area is suitable. Feed availability in ASLNP is scarce even during rainy seasons. Especially the open woodlands are subject to overgrazing. Such shortage forces the inhabitants to cut trees for charcoal making to buy animal feed and non-food consumables. While more than 95% of the inhabitants in the park expanded their agriculture lands, only 13.3% of the farmers managed to produce cereals for market. The application of low cost remote sensing and GIS methods provided ample information that enables to conclude that low productivity and household food insecurity are the main driving forces behind land cover changes that are negatively affecting the natural and semi-natural ecosystems in the central and southern Rift Valley of Ethiopia. The restoration of natural ecosystems or conservation of biodiversity can be achieved only if those driving forces are tackled sustainably.

>Magister Scientiae - MSc
The class Actinobacteria consists of a heterogeneous group of filamentous, Gram-positive bacteria that colonise most terrestrial and aquatic environments. The industrial and biotechnological importance of the secondary metabolites produced by members of this class has propelled it into the forefront of metagenomics studies. The Ethiopian Rift Valley lakes are characterized by several physical extremes, making it a polyextremophilic environment and a possible untapped source of novel actinobacterial species. The aims of the current study were to identify and compare the eubacterial diversity between three geographically divided soda lakes within the ERV focusing on the actinobacterial subpopulation. This was done by means of a culture-dependent (classical culturing) and culture-independent (DGGE and ARDRA) approach. The results indicate that the eubacterial 16S rRNA gene libraries were similar in composition with a predominance of α-Proteobacteria and Firmicutes in all three lakes. Conversely, the actinobacterial 16S rRNA gene libraries were significantly different and could be used to distinguish between sites. The actinobacterial OTUs detected belonged to both the Rubrobacterales and Actinomycetales orders with members of the genus Arthrobacter being found in all three lakes. Geochemical properties were significantly different between the lakes, although more than one property attributed to the variance between community compositions. The diversity detected in the culture-based study differed significantly and all isolates belonged to the genus Streptomyces. Two novel strains were characterized by means of phylogenetic (16S rRNA gene sequence), physiological, morphological and biochemical analyses. Both novel isolates were capable of growing under "extreme" conditions- pH 12, 10% NaCl and 45°C. Partial enzyme characterization revealed that both strains produced xylanase enzymes that were active at pH 6.5 and 8.5 with an increase in activity up to 45°C. The results obtained revealed a previously undetected diversity of actinobacteria in the Ethiopian Rift Valley with a potentially novel subpopulation adapted to haloalkaline conditions. The low 16S rRNA sequence similarity of a substantial proportion of the libraries suggests that culture-based isolation may play a vital role in deciphering the community fingerprint.
The National Research Foundation and the Norwegian Research Council

Middle Awash basin, located in the complex volcanic centre of the Ethiopian Rift valley, is one of the drought prone areas marked by considerable water supply problems. Due to lack of surface waters, groundwater remains the sole resource supplying water for domestic and livestock. However, its effective use has been hampered due to the complex aquifer system of this basin. In this study, multidisciplinary method has been applied to characterize the hydrogeological system of this complex volcanic basin. The combined results from datasets show two distinct aquifer systems linked to geology and physiographic location. The Ca-alkaline rocks like basalt, ignimbrite, and trachybasalt form aquifers in the mountain regions whereas the Na-alkalne rocks which include scoria, pumice, tuff, and volcanoclastics are main aquifers in rift floor. Ground waters circulating in the highland areas are slightly mineralized and are Ca-Na-HCO3 type. On the other hand, ground waters in the rift floor are Na-HCO3-Cl types and are highly mineralized as well as contain high load of fluoride much higher than the permitted standard. Rivers hydrograph, hydrochemistry, environmental isotope, and 2D tomography are in good agreement showing fast percolation of rainfall and strong interaction between surface waters and ground waters. Result from numerical groundwater flow modeling further indicates the strong interaction between groundwater and surface waters in the form of losing and gaining
Le bassin central d'Awash, situé dans le centre volcanique complexe de la Vallée du Rift éthiopien, est un des secteurs les plus touchés par la sécheresse et par des problèmes considérables d'approvisionnement en eau. En raison du manque d'eau de surface, l'eau souterraine reste la ressource unique fournissant l'eau potable. Cependant, l'exploitation effective de l'eau souterraine s'est heurtée à la méconnaissance du système hydrogéologique complexe de ce bassin. Dans cette étude, une approche pluridisciplinaire a été mise en oeuvre pour caractériser l'hydrogéologie de ce bassin volcanique complexe. Les résultats couplés de l'ensemble des données montrent deux systèmes aquifères distincts liés à la géologie et à la localisation physiographique. Les roches Ca-alcalines comme le basalte, l'ignimbrite et le trachybasalte forment des aquifères dans les régions de montagne tandis que les roches Na-alcalines qui incluent les scories, la pierre ponce, les tufs et les volcanoclastiques constituent les principaux aquifères au niveau du plancher du rift. Les eaux souterraines circulant dans les secteurs montagneux sont légèrement minéralisées et sont de type Ca-Na-HCO3. Par contre, les eaux souterraines du plancher du rift sont de type Na-HCO3-Cl, sont fortement minéralisées et contiennent une charge en fluorure beaucoup plus élevée que les normes permises. Les résultats de diverses approches (hydrogrammes des fleuves, hydrochimie, isotopes environnementaux et tomographie 2D) sont concordants et montrent une percolation rapide des eaux de pluie et une forte interaction entre les eaux de surface et les eaux souterraines. Les résultats de modélisation numérique confirment la forte interaction eau souterraine - eaux de surface

Fluoride is present in all type of water sources, but levels beyond the current World Health Organization guideline of 1.5 mg/L can be very harmful for people’s health. Due to the volcanic nature of rocks in the Ethiopian Rift Valley, groundwater is contaminated with fluoride, and studies have even recorded levels up to 26 mg/L. These excessive levels are affecting more than 14 million women and children in Ethiopia. Providing population with safe and clean water could help to achieve the Sustainable Development Goal 6 (i.e. Ensure availability and sustainable management of water and sanitation for all) from the United Nations. Membrane distillation systems have been extensively tested in literature, proving to be effective in removing fluoride, even at higher concentration levels (500 mg/L). Membrane distillation is a heat driven system that works under feed water temperatures below 100 ºC. Renewable energy sources such as geothermal, solar or biomass can be used to provide that heat. This report evaluates techno-economically different technologies using TRNSYS: flat plate solar collectors, evacuated tube solar collectors and biogas from animal dung, as heat source for the membrane distillation unit. The size of the hypothetical installations was optimized to cover the demand of 30 households. Several indicators were calculated to compare the different technologies: specific energy demand, water production, and efficiency of the systems. Investment costs and operation and management costs were considered to calculate total costs and payback period of the different installations. The results show that the best techno-economic option to be installed is a hybrid model that includes a combined heat and power unit powered by biogas and evacuated tube collectors, as can meet the demand with one membrane distillation unit and also supplies electricity and biogas for cooking. However, depending on the specific location, the availability of solar radiation and manure can vary, and consequently the best option will change. In case the existence of livestock is limited, three membrane distillation units coupled with 85 m2 of evacuated tube collectors can cover the demand. If the availability of sun is limited one membrane unit coupled with a standalone biogas unit can be considered. Flat plate collectors are never the best option, as they require the biggest investment cost. Nevertheless, the existence of local manufacturers can decrease the costs.
Fluor finns i alla typer av vattenkällor, men koncentrationer som ligger över nuvarande Världshälsoorganisationens riktlinjer (max 1.5 mg/L) kan vara skadlig för hälsan. Grundvatten vid Ethiopian Rift Valley innehåller höga fluorhalter på grund av geologiska orsaker, och studier har visat nivåer upp till 26 mg/L. Sådana höga halter påverkar över 14 millioner Etiopiska kvinnor och barn negativt. Att tillgodose befolkningen med säkert och rent dricksvatten skulle bidra till uppfyllelsen av FN:s Hållbarhetsmål nr 6 (Säkerställa tillgång till och hållbar vatten- och sanitetsförvaltning för alla). Membrandestillering har testats grundligt och har visat sig att vara en effektiv teknik för fluorseparering även vid höga halter (över 500 mg/L). Membrandestillering ar en värmedriven process som utnyttjar källor under 100 ºC. Värmen kan fås från förnybara energikällor som geotermisk energi, solenergi och biobränsle. Denna rapport presenterar en tekno-ekonomisk utvärdering av olika teknik med TRNSYS: plan solfångare, vakuumrörsolfångare och biogas från boskapsgödsel.  Storleken hos de undersökta systemen optimerades för att täcka behovet av 30 hushåll. Flera indikatorer beräknades för att jämföra de olika teknikerna: specifika energibehov, vattenproduktion och systemens verkningsgrader. Investeringskostnaderna och drift- och underhållskostnaderna låg som grund för att bestämma bruttokostnaderna och återbetalningstiderna av de olika systemen. Resultaten visar att den mest fördelaktiga konfigurationen består av en hybrid av biogas och vakuumrörsolfångare. Detta system tillgodoser vattenbehovet och dessutom levererar el och gas för matlagning. Tillgången till solenergi och gödsel spelar en viktig roll när det gäller systemvalet. Om tillgång till gödsel är begränsad kan efterfrågan täcks genom tre membrandestilleringsenheter kopplade till 85 m2 vakuumrörsolfångare. Däremot om solenergin är begränsad kan ett system med en membrandestilleringsenhet kopplade till en biogasanläggning tillgodose vattenbehovet. Plan solfångare är aldrig ett bra alternativ eftersom de kräver höga investeringskostnader. Tillgång till lokal tillverkning kan dock minska sådana kostnader.

Fluoride is present in all type of water sources, but levels beyond the current World Health Organization guideline of 1.5 mg/L can be very harmful for people’s health. Due to the volcanic nature of rocks in the Ethiopian Rift Valley, groundwater is contaminated with fluoride, and studies have even recorded levels up to 26 mg/L. These excessive levels are affecting more than 14 million women and children in Ethiopia. Providing population with safe and clean water could help to achieve the Sustainable Development Goal 6 (i.e. Ensure availability and sustainable management of water and sanitation for all) from the United Nations. Membrane distillation systems have been extensively tested in literature, proving to be effective in removing fluoride, even at higher concentration levels (500 mg/L). Membrane distillation is a heat driven system that works under feed water temperatures below 100 ºC. Renewable energy sources such as geothermal, solar or biomass can be used to provide that heat. This report evaluates techno-economically different technologies using TRNSYS: flat plate solar collectors, evacuated tube solar collectors and biogas from animal dung, as heat source for the membrane distillation unit. The size of the hypothetical installations was optimized to cover the demand of 30 households. Several indicators were calculated to compare the different technologies: specific energy demand, water production, and efficiency of the systems. Investment costs and operation and management costs were considered to calculate total costs and payback period of the different installations. The results show that the best techno-economic option to be installed is a hybrid model that includes a combined heat and power unit powered by biogas and evacuated tube collectors, as can meet the demand with one membrane distillation unit and also supplies electricity and biogas for cooking. However, depending on the specific location, the availability of solar radiation and manure can vary, and consequently the best option will change. In case the existence of livestock is limited, three membrane distillation units coupled with 85 m2 of evacuated tube collectors can cover the demand. If the availability of sun is limited one membrane unit coupled with a standalone biogas unit can be considered. Flat plate collectors are never the best option, as they require the biggest investment cost. Nevertheless, the existence of local manufacturers can decrease the costs.
Fluor finns i alla typer av vattenkällor, men koncentrationer som ligger över nuvarande Världshälsoorganisationens riktlinjer (max 1.5 mg/L) kan vara skadlig för hälsan. Grundvatten vid Ethiopian Rift Valley innehåller höga fluorhalter på grund av geologiska orsaker, och studier har visat nivåer upp till 26 mg/L. Sådana höga halter påverkar över 14 millioner Etiopiska kvinnor och barn negativt. Att tillgodose befolkningen med säkert och rent dricksvatten skulle bidra till uppfyllelsen av FN:s Hållbarhetsmål nr 6 (Säkerställa tillgång till och hållbar vatten- och sanitetsförvaltning för alla). Membrandestillering har testats grundligt och har visat sig att vara en effektiv teknik för fluorseparering även vid höga halter (över 500 mg/L). Membrandestillering ar en värmedriven process som utnyttjar källor under 100 ºC. Värmen kan fås från förnybara energikällor som geotermisk energi, solenergi och biobränsle. Denna rapport presenterar en tekno-ekonomisk utvärdering av olika teknik med TRNSYS: plan solfångare, vakuumrörsolfångare och biogas från boskapsgödsel. Storleken hos de undersökta systemen optimerades för att täcka behovet av 30 hushåll. Flera indikatorer beräknades för att jämföra de olika teknikerna: specifika energibehov, vattenproduktion och systemens verkningsgrader. Investeringskostnaderna och drift- och underhållskostnaderna låg som grund för att bestämma bruttokostnaderna och återbetalningstiderna av de olika systemen. Resultaten visar att den mest fördelaktiga konfigurationen består av en hybrid av biogas och vakuumrörsolfångare. Detta system tillgodoser vattenbehovet och dessutom levererar el och gas för matlagning. Tillgången till solenergi och gödsel spelar en viktig roll när det gäller systemvalet. Om tillgång till gödsel är begränsad kan efterfrågan täcks genom tre membrandestilleringsenheter kopplade till 85 m2 vakuumrörsolfångare. Däremot om solenergin är begränsad kan ett system med en membrandestilleringsenhet kopplade till en biogasanläggning tillgodose vattenbehovet. Plan solfångare är aldrig ett bra alternativ eftersom de kräver höga investeringskostnader. Tillgång till lokal tillverkning kan dock minska sådana kostnader.

A systems approach in research offers to examine the bio-physical constraints and decision-making of farmers exposed to climate variability. In this project, a systems perspective was achieved by combining computer-based simulation modelling, farmer surveys, and field experimentation to explore current and potential agronomic management practices crucial to smallholder maize (Zea mays L.) farmers to manage climate risks in the semi-arid regions of Ethiopia. The study aimed at investigating a suit of management options to identify opportunities that can improve crop productivity while reducing the production risk in smallholder maize-based cropping systems in the Central Rift Valley (CRV) Ethiopia. To establish better insights into farmers’ perceptions of, and management responses to climate variability, farmer surveys or rapid rural appraisal (RRAs) were conducted. The RRAs were conducted in three villages from two districts (Bosset and Adamitulu Jido-Kombolcha (AJK) in the CRV region of Ethiopia. Information collected from the interviews of 60 farmers and two focus group discussions in the study area were used to acquire baseline information of how farmers in the CRV perceive climate variability, particularly rainfall variability, and how their understanding of climate variability translates into farm management decisions and actions. During RRAs, assessments were made regarding farmers’ perceptions of the local climate variability, along with how farmers’ observation and knowledge of the seasonal climate affect their agronomic decisions. Generally, farmers gave similar criteria to describe seasonal climatic conditions and to distinguish seasons as ‘good’, ‘average’ or ‘bad’ indicating a shared experience. Farmers’ perceptions of seasonal climate variability and risk were mainly related to seasonal rainfall parameters in regards to crop growth and yield. Furthermore, in most cases, farmers’ ratings of season ‘types’ were in agreement with the official classification published by the National Meteorological Service of Ethiopia. Of the rainfall characteristics, total amount of seasonal rainfall was rated less critical than variations in the timing of rainfall onset and dry spells during the growing season. The historical pattern, local weather observations, and other indicators allowed farmers to form expectations of what the rainfall conditions are likely to be in the season ahead. Many of the farmers agronomic decisions are based on the actual and expected seasonal rainfall, however, not all farmers respond in the same way. Farmers indicated that rainfall indicators are particularly important as many of the key management decisions (i.e., sowing date, cultivar choice, the portion of land allocated to maize and other crop species) are flexible according to the timing of the onset of the seasonal rains. Historically, farmers used to sow their late maturing maize if rain started early in the Belg season (March/April–May), however, many farmers stated that they had noticed that the onset and distribution of early seasonal rainfall had become less reliable and more variable from the 1990s onwards. Farmers explained Belg season as unreliable due to post-sowing dry spells of varying length that can risk their crop to fail and they often need to re-sow. Still, around 30% of the respondents at Bosset and 60% at AJK opted to sow a late-maturing cultivar if Belg rain did occur, while the remaining 60% of farmers would wait until June if rain established well in the Kiremt season (June–September). In this study, less than 30% of the respondents applied mineral nitrogen (N) fertiliser, at sub-optimal rates, while 70% did not apply N fertiliser at all. Of the 70% of respondents who did not apply N fertiliser, nearly 40% of the respondents assumed that their fields were sufficiently fertile or non-responsive at all and there would be no yield advantage from applications of commercial N fertiliser. In 2012, a maize field experiment was conducted season at Melkassa, in the CRV, to obtain a comprehensive quality data set suitable for modelling purposes and to evaluate the responses of two locally adapted maize cultivars to contrasting sowing dates and N fertiliser application rates. Data included daily weather, crop properties (phenology, growth pattern, plant N concentration, grain and biomass yield of the locally adapted and medium-maturing maize cultivar, Melkassa-2), soil water and N characteristics and crop management details, along with the initial conditions of the soil profile (soil water and mineral N content and surface residue). These data were used to parameterise the Agricultural Production Systems sIMulator (APSIM) for one of dominant soil type representative of ‘good cropping conditions’ in the region. The parameterised model was evaluated against independent data from six maize experiments conducted between 2006 and 2012 at Melkassa. The model was evaluated by comparing the simulated and observed phenology, grain and biomass yields of maize cv. Melkassa-2 across a range of production situations at Melkassa. Generally, evaluation of the parameterised model against independent data showed that it was able to predict key crop responses including crop phenology, grain yield and biomass production as evidenced by different statistical indices for the goodness of fit between the simulated and observed values. The results demonstrated that APSIM-Maize is reliable and suitable for scenario analyses of maize production systems in semi-arid environments of Ethiopia. Subsequently, the APSIM-Maize model was configured to run long-term simulation experiments to explore the maize yield response to agronomic factors, which farmers who participated in the RRAs had identified as being important in managing climate risks. In the long-term simulations, a combination of varying sowing window, cultivar type and N fertiliser rates were considered to represent local management practices of typical farmers. In addition, agronomic recommendations of research and extension services were simulated along with other agronomic management measures. Simulations of maize yield were run for each year of the available historical weather records from weather stations nearby to the study villages (i.e., 34 years ranging from 1982 to 2015 at Adamitulu and 39 years ranging from 1977 to 2015 at Melkassa). For the sowing windows, early, normal and late sowing dates were considered. Cultivar choices included early-, medium- and late-maturing maize cultivars and three rates of N fertiliser were applied: 0 kg N ha\(^{-1}\) (N0), 25 kg N ha\(^{-1}\) (N25), and 50 kg N ha\(^{-1}\) (N50). Altogether, there were 54 simulation scenarios to analyse for both Adamitulu and Melkassa. The production risk associated with each combination of agronomic factors were estimated thereby creating best management options that farmers may possibly consider in the future when making decisions related to maize production under their local environment, which is characterised by highly variable and uncertain climate. Early sowing (March/April–May) ensured a sowing opportunity in more years compared to normal or late sowing, however, the likelihood of complete crop failure was greatest for early sowing (10%), due to a false start of rain or a risk of post-sowing dry spells, with risk decreasing as sowing was delayed from a normal (5%) to late window (<5%) during the Kiremt season. For late sowing, crop failure was unlikely, except for the late-maturing cultivar at Adamitulu where crop failure was ~15% more likely. For the early sowing, the late-maturing cultivar out-yielded the earlier cultivars at all levels of cumulative probability in 90% of the years. For the normal sowing, there was at least 88% likelihood of yield gain from selecting late-maturing cultivars compared to earlier cultivars irrespective of the N rate applied. At Adamitulu, the yield advantage of the late-maturing cultivar was greater if sown early (1 March–30 May) instead of later (early- to mid-June or mid- to end-June). At Melkassa, the yield gain was greater if the late-maturing cultivar was sown during the normal (1–15 June) and late (16–30 June) sowing window rather than early (1 April–30 May). For both locations, the long-term median yield of the late cultivar was greater than the early or normal cultivar, especially in high to average yielding years. In contrast, selecting an early cultivar reduced median yield. Irrespective of sowing time, there was at least an 85% likelihood of a yield loss from using an early cultivar than the medium and the late cultivars. However, for the late sowing at Adamitulu, the likelihood of yield penalties was only 65% when using an early or medium cultivar instead of the late one. Application of N fertiliser produced greater yields compared to unfertilised maize in at least 85% of the years regardless of the sowing window and cultivar type. With application of N50, there was a 65% likelihood that the yield gain would be more than the maximum yield that could ever be achieved with the application of N25. Averaged across locations, application of fertiliser could result in increases in the long-term median yields of 77% at N25 and 133% at N50 (2.7 and 3.5 t ha\(^{-1}\) vs. 1.7 t ha\(^{-1}\)) compared to the baseline N0. There were large shifts in cumulative distribution functions towards greater yields with application of either N25 or N50 compared to N0, although to varying degrees depending on the sowing time and the cultivar type. For a late cultivar sown at early and normal sowing windows, and for a medium cultivar sown late, the long-term simulations showed that application N25 could increase yield in more than 95% of the seasons without affecting the inter-seasonal variations in yield (as indicated by CV%) compared to N0. On the other hand, the locally recommended rate of N50 reduced maize yields in as much as 20% of the seasons compared to the farmer baseline N application strategy. Farmers are guaranteed a minimum yield of 2.5 t ha\(^{-1}\) in 75–90% of the simulated seasons when they applied at least N25, whereas this was only possible in 17–35% of the simulated seasons when no N was applied. Although the application of N fertiliser is not a standard practice in the region, the scenario analyses highlighted the importance of N fertiliser to boost crop productivity without inducing additional inter-seasonal variations. In conclusion, financially constrained and risk-averse farmers in the study areas, who traditionally grow maize without application of commercial N fertiliser, need to be educated about the benefits of using N fertiliser at a modest rate of application (i.e., 25 kg N ha\(^{-1}\)). This low risk strategy could be a stepping-stone to feasible intensification of the smallholder maize system in the CRV region. This thesis demonstrated that understanding the various aspects of the smallholder farmers including their local management situation, aspirations and risk preference and production objectives can be achieved using a participatory research approach. By engaging farmers in focus group discussions and individual interviews, along with crop simulation modelling using APSIM, climatic risks and their interaction with changes in agronomic management decisions and technological strategies for improving the performance of the farm system that suit the biophysical environment and socioeconomic conditions of the farming community can be explored. As a result, relevant and targeted ex-ante information can be generated about crop yield responses to various combinations of climate, soil and management factors. This enables researchers to provide farmers and their extension advisors with quantifiable information about production levels and risks as a consequence of the various agronomic management options. Ultimately, this will help support farmers shape their local practices and guide their strategic decisions in the face of climate variability and uncertainty.

This research was conducted in one of the districts in the Oromia region located in the Central Rift Valley to assess the problem of soil erosion and deforestation and to determine how these drivers of land degradation affect the livelihoods of farmers. The research was a case study undertaken in an identified micro-watershed making use of the questionnaire interview method. A household sample was obtained using a simple random sampling technique; Information interviews were conducted with community representatives, district level experts and development agents who worked in the community. The objective of the research was to assess the levels of soil erosion and deforestation and the impact on the livelihoods of the community. Research methods were questionnaire and direct observation. The results of the study indicated that the effects of soil erosion and deforestation on land productively, agriculture and livestock production at large, had a negative effect on livelihoods of the community members. Recommendations based on the research affirm the necessity to undertake large-scale natural resource management starting with community-based watershed management thereby reducing the impact of land degradation on livelihoods of farmers and ensuring food security and sustainable land management.
Agriculture, Animal Health & Human Ecology
M.A. (Human Ecology)

Agroforestry parkland systems, in which a low population density of mature trees occur scattered across farmland, are common land use systems in Ethiopia. Parkland trees, including Faidherbia albida (Delile) A.Chev, have been associated with improved soil fertility and crop productivity and they provide ecological services such as carbon sequestration and biodiversity conservation. However, trees can also have detrimental impacts on understory crops because of competition for resources such as light, nutrients and water. Thus, it is necessary to select suitable tree and crop species as well as management options in order to limit competition and maximize synergies. Agroforestry research and modelling can be applied to understand and accurately predict the effects of tree management on crop growth. This thesis presents research aiming to explore and simulate maize production under different tree and crop management factors in a Faidherbia albida parkland agroforestry system of the Central Rift Valley, Ethiopia, as well as to estimate its carbon sequestration potential. The approach included two field experiments. The first experiment examined how shading affected maize growth and development (using a maize-only field trial with artificial shading). The second experiment focussed on how maize production was impacted by tree pruning, distance from the tree and fertiliser interactions. The APSIM (Agricultural Production Systems simulator) model was used to simulate the effect of these interactions on maize yield. Carbon sequestration in both tree biomass and soil of F. albida trees was estimated by harvesting three average F. albida trees (unpruned trees from the second experiment) and taking soil samples under and beyond tree canopies. Reduced radiation, caused by artificial shading, had a significant negative effect on maize productivity; 50% reduction in incident radiation led to 56% reduction in maize yield, and a 75% reduction in radiation resulted in 64% reduction in yield. This highlighted the need to minimise light competition (shading) in agroforestry systems by managing trees, for example by crown pruning. Soil nutrients and moisture availability were higher under trees than away from tree trunks. This resulted in higher biomass and yield of maize under trees (2-6 m radius of tree canopies) compared to crop-only plots in both growing seasons, and regardless of pruning and fertiliser levels. Overall, there was 56% more grain yield under trees across the two seasons. Fertilisation further increased yields by an average of 15% under tree canopies compared to crop-only plots in both years, but more so in 2016 (when rainfall was higher). Crop biomass and yield were lower under unpruned trees (0–2 m) relative to the totally pruned and 50% pruned trees due to reduced light available to crops and in the absence of leaf fall. Faidherbia albida tree density is sparse (5.8 trees ha\(^{-1}\)) in the study area. It was estimated that trees stored about 2 t C ha\(^{-1}\) in their above-ground biomass and 0.76 t C ha\(^{-1}\) below-ground; and there was 34 t C ha\(^{-1}\) more in soil (0–80 cm depth) under trees than in crop-only areas. However, this rate is low relative to soil C sequestration by other agroforestry systems. This was attributed to the low tree population density in the study area, but could be increased by encouraging farmers to protect planted seedlings or natural regeneration. The APSIM model adequately simulated maize grain yield response to shading (under maize only situations), based on field measurements from the first experiment. The model also reasonably predicted the response of maize yield in low and high rainfall years to tree pruning and fertiliser (N)applications under tree canopies, for which model calibration and validation were based on the second experiment. A virtual experiment indicated that optimal maize yield could be obtained at lower rates of fertilisation (<50 kg N ha\(^{-1}\)) under trees than away from them, and that under tree plots (2-6 m) would have the highest yields in most years when fertiliser was not available. High yields under trees were due to increased nutrient and water availability. However, modelled scenarios also highlighted the presence of competition between trees and crops close to tree trunks. For example, plots near to tree trunks (0-2 m) were simulated to consistently produce less maize yield than crop-only plots, which (without trees) also had the highest yields in most years when adequate fertiliser was applied. Thus, we concluded that proper selection and management of agroforestry systems may provide a sustainable alternative for enhancing crop productivity by resource poor farmers. Generally, the study demonstrated that, depending on the extent that trees can improve soil fertility, incorporating them into farmlands could improve crop productivity and deliver ecosystem services such as carbon sequestration. The study also suggested that maize productivity could be improved by crown pruning, and by preferentially applying fertilisers in normal (about average rainfall) and wet (above average rainfall) years. These results need to be considered in a farm-scale livelihood context, which was beyond the scope of the present research. Further research should employ a whole farm modelling approach, in order to understand the combined interactions of agroforestry system components, and to provide recommendations to farmers and policy makers.

The Social Capital approach to development is based on the premise that both cognitive and structural aspects of a given society determine the level of development performance. It is argued that norms of trust and reciprocity, networks, and mutual aid govern interaction among people, hold them together, facilitate opportunities to manage common property and pursue common goals, and ultimately contribute to development by facilitating their cooperation and collective action. In this thesis I explore the relationship between social capital and development by analysing the performance of household wellbeing in a given community. Two dominant views on social capital and the outcomes of development performance are currently in prominence in the development discourse. This debate centres on whether social capital is a sufficient cause on its own or whether it needs intermediary actors. The social capital theory argues that the development performance of a particular community can be explained directly by the prevailing level of social capital, and that the underlying levels of trust, social norms and networks are sufficient to explain development. On the other hand, the school of thought that supports the need for intermediary actors argues that social capital is unable to influence development performance at higher levels. If a larger impact and a more precise outcome are expected, intermediary actors who facilitate interest formation, aggregation and representation are necessary. Without them, social capital remains largely inactive and dormant. In exploring the possible link between the two variables, this thesis supports the second premises, introducing the notion of intermediary actors that might activate the stock of social capital and its performance on household wellbeing. The need to explore the relationship between the two variables demanded empirical research. The research was conducted in the rural villages of Oromia regional State of Ethiopia. Based on the empirical evidence, the relationship between the stock of social capital and performance in household wellbeing is generally positive. A large stock of social capital is generally accompanied by a higher level of performance in household wellbeing. However, I argue that social capital is only truly social when activated by an intermediary development actor. Failing this, though it contributes significantly to village solidarity and unity, social capital remains inactive and dormant. Therefore, the general conclusion of this thesis is that social capital matters, but its utilisation by intermediary agencies matters more.