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Article 0 Reads 0 Citations Tropical wetland ecosystem service assessments in East Africa; A review of approaches and challenges Published: 01 April 2018
Environmental Modelling & Software, doi: 10.1016/j.envsoft.2018.01.022
East African wetlands are hotspots of ecosystem services, particularly for climate regulation, water provision and food production. We review the ability of current approaches to ecosystem service assessments to capture important social-ecological dynamics to provide insight for wetland management and human wellbeing. We synthesise evidence of human influences on wetlands and gauge the suitability of models and tools for simulating spatial and temporal dynamics, and land management on multiple ecosystem functions and services. Current approaches are largely unsuitable for advancing knowledge of social-ecological system dynamics and could be greatly improved with inter-disciplinary model integration to focus upon interactions between multiple ecosystem functions and services. Modelling can alleviate challenges that tropical wetland ecosystem services management faces and support decision-making of land managers and policymakers. Better understanding of social-ecological systems dynamics is crucial in East Africa where societies are vulnerable to poverty and climate variability, whilst dependent upon agrarian-ecological based economies.
Article 0 Reads 0 Citations Are smallholder farmers willing to pay for a flexible balloon biogas digester? Evidence from a case study in Uganda Published: 01 April 2018
Energy for Sustainable Development, doi: 10.1016/j.esd.2018.01.008
Biogas technology, as a pro-poor renewable energy source, has been promoted in Uganda through the use of fixed dome and floating drum digester designs. However, these designs have proved to be too expensive for the average Ugandan household to afford. A cheaper flexible balloon digester has been proposed to increase uptake. However, there has been lack of evidence on household's willingness to pay (WTP) for the flexible balloon digester and the factors affecting adoption of this alternative design. Primary data were obtained from survey of experimental households and 144 ‘non-biogas’ households in central Uganda. A logistic regression model was used to estimate household's WTP and determine the factors that influence WTP. Results reveal that the majority of surveyed households showed their WTP, but an average household's maximum WTP (US$52) was ten times less than the actual cost of an imported flexible ballon digester unit (US$512). The results further indicate that household size, education level, gender and age of the household head, number of livestock owned, total land area owned and a household's perception on technology significantly influenced the WTP. Thus, government and NGOs interested in promoting this design should pay due attention on ensuring the availability of affordable flexible balloon digester from local sources. Otherwise, the focus should be on promoting either different biogas designs or alternative affordable renewable energy technologies rather than the flexible balloon digester.
Article 0 Reads 0 Citations Household energy and recycling of nutrients and carbon to the soil in integrated crop-livestock farming systems: a case ... Published: 28 June 2017
GCB Bioenergy, doi: 10.1111/gcbb.12459
Soil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha−1 yr−1 nitrogen (109(±8) kg yr−1 per household), 13.9(±0.3) kg ha−1 yr−1 phosphorus (26(±2) kg yr−1 per household), 79(±2) kg ha−1 yr−1 potassium (150(±11) kg yr−1 per household) and 2100(±40) kg ha−1 yr−1 organic carbon (3000(±300) kg yr−1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr−1. However, this is less than their value as fuels, which was 490(±20) US$ yr−1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found.
Article 0 Reads 0 Citations Water for small-scale biogas digesters in Sub-Saharan Africa Published: 02 May 2016
GCB Bioenergy, doi: 10.1111/gcbb.12339
Biogas could provide a more sustainable energy source than woodfuels for rural households in Sub-Saharan African. However, functioning of biogas digesters can be limited in areas of low water availability. The water required is approximately 50 dm3 day−1 for each cow and 10 dm3 day−1 for each pig providing manure to the digester, or 25 (±6) dm3 day−1 for each person in the household, using a digester volume of 1.3 (±0.3) m3 capita−1. Here we consider the potential of domestic water recycling, rainwater harvesting and aquaculture to supply the water needed for digestion in different countries of Sub-Saharan Africa. Domestic water recycling was found to be important in every country but was usually insufficient to meet the requirements of the digester, with households in 72% of countries needing to collect additional water. Rooftop rainwater harvesting also has an important role, iron roofs being more effective than thatched roofs at collecting water. However, even with an iron roof, the size of roof commonly found in Sub-Saharan Africa (15 m2 to 40 m2) is too small to collect sufficient water, requiring an extra area (in m2) for each person of (where R is the rainfall in mm). If there is a local market for fish, stocking a pond with tilapia, fed on plankton growing on bioslurry from the digester, could provide an important source of additional income and hold the water required by the digester. In areas where rainfall is low and seasonal, the fishpond might be stocked only in the rainy season, allowing the pond to be covered during the dry period to reduce evaporation. If evaporative losses (E in mm) exceed rainfall, an extra catchment area is needed to maintain the water level in the pond, equivalent to approximately m2 for each person in the household.This article is protected by copyright. All rights reserved.
Article 0 Reads 3 Citations Spatial and temporal dynamics of soil organic carbon in landscapes of the upper Blue Nile Basin of the Ethiopian Highlan... Published: 01 February 2016
Agriculture, Ecosystems & Environment, doi: 10.1016/j.agee.2015.11.019
Highlights•We studied soil organic C and land use in the upper Blue Nile Basin, Ethiopia.•There is more recalcitrant organic matter in shrub- than in grass- or croplands.•It is more difficult to sequester C into an eroded than a non-eroded soil.•Conversion to shrubland shows high potential to restore recalcitrant soil C.•Current management at the sites of croplands and grasslands is not sustainable. AbstractThe purpose of this study was to characterize the soil organic carbon dynamics associated with four land-uses (cropland, grassland, shrubland, and forestland) in the upper Blue Nile Basin of the Ethiopian Highlands. We collected diverse biophysical data to allow spatial variability of soil organic carbon and factors contributing to this variation to be determined statistically, and used well established simulation models to interpret the data, predict long-term carbon dynamics and determine the potential for improvements in soil quality and mitigation of greenhouse gas emissions. The spatial variation in soil organic carbon in the 0–20 cm soil depth was significant across study areas (P < 0.01, 21.6 g kg−1–37.8 g kg−1), and between land-uses (P < 0.05, 27.9 g kg−1 in cropland and 43.0 g kg−1 soil in forestland). In a multiple linear regression model, among the 11 explanatory variables used, four (total nitrogen, shrubs, trees and land use) showed a significant positive effect (P < 0.01), while three (impact of grazing, impact of erosion and clay) showed a significant negative effect (P < 0.01). Simulations using the assumption of steady state to estimate carbon dynamics suggested that plant inputs from croplands are generally lower than grass or shrublands, resulting in build-up of recalcitrant organic matter in shrublands compared to grass or croplands. Erosion results in a decline in both the absolute and relative amounts of carbon in recalcitrant pools, but the more active pools remained unchanged, meaning that the overall activity of soil organic matter is increased when the soil is eroded, and it becomes more difficult to sequester soil carbon. More rapid decrease in soil organic carbon is likely to be due to increased erosion, persistent removal of organic materials, grazing pressures, and higher rate of decompositions in cropland and grazing land-uses. Conversion to shrubland shows high potential to quickly restore eroded soils and build up a pool of recalcitrant soil carbon, suggesting that management of land using periodic 20 year exclosures, preventing cropping and grazing and allowing shrubland succession, could be beneficial in restoring degraded soils. Simulations using a calibration approach, rather than assuming steady state, corroborated these findings, suggesting that after 30 years of current management, croplands will deplete soil organic carbon by 5.6, 7.1 and 7.2 t ha−1, and grasslands by 3.5, 3.9 and 2.7 t ha−1, while shrublands will build-up soil organic carbon by 0.6, 0.1 and 1.3 t ha−1 at study sites. At one study site, forests, will further increase soil organic carbon by 6.7 t ha−1 after 30 years. The significant positive impact of shrubs and trees on soil organic carbon suggests the need to focus on introduction of agroforestry systems in crop and grasslands.
BOOK-CHAPTER 0 Reads 0 Citations Mathematical Modeling of Greenhouse Gas Emissions from Agriculture for Different End Users Published: 01 January 2016
Advances in Agricultural Systems Modeling, doi: 10.2134/advagricsystmodel6.2013.0038