Institute of Geography and Development Studies

Permanent URI for this collectionhttps://dspace.njala.edu.sl/handle/20.500.144402/147

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Start date: 2022Has files: No

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Now showing 1 - 10 of 27
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    Rice biophysical parameter retrieval with optical satellite imagery: a comparative assessment of parametric and non-parametric models
    (Taylor & Francis, 2022-05-30) Mansaray, Lamin R.
    This article presents a comparison of parametric and non-parametric models in rice biomass and leaf area index (LAI) retrieval using optical satellite imagery. Four parametric models including the linear, quadratic, logarithmic and exponential models, and four non-parametric models that include RF, SVM, kNN, and GBDT were applied, respectively, on the optical satellite dataset. GBDT produced the most accurate biomass estimates (RMSE of 191.8 g/m2) before heading and the quadratic model produced the most accurate biomass estimates (RMSE of 364.7 g/m2) after heading. RF registered the most accurate LAI estimates (RMSE of 0.79 m2/m2) before heading, whereas the quadratic model recorded the most accurate LAI estimates (RMSE of 1.04 m2/m2) after heading. Non-parametric models outperformed their parametric counterparts at before heading, whereas the reverse is the case after heading. These findings provide a guide to the optimal choice of empirical models for rice biomass and LAI retrieval with optical imagery.
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    Propagation of Meteorological Drought to Agricultural and Hydrological Droughts in the Tropical Lancang–Mekong River Basin
    (Multidisciplinary Digital Publishing Institute, 2023-12-09) Feng, Ganlin
    In the past several decades, drought events have occurred frequently around the world. However, research on the propagation of drought events has not been adequately explored. This study investigated the drought propagation process from meteorological drought to agricultural drought (PMAD) and from meteorological drought to hydrological drought (PMHD) using a 72-year reanalysis dataset in the tropical Lancang–Mekong River Basin. Firstly, we used a new method—Standardized Drought Analysis Toolbox—to construct drought indices. Then, a linear method (Pearson correlation analysis) and a nonlinear method (mutual information) were used to investigate the drought propagation process. Cross-wavelet analysis and wavelet coherence analysis were employed to explore the statistical relationship among the three drought types. Finally, the random forest method was applied to quantify the major factors in drought response time (DRT). The results revealed the following: (1) both linear and nonlinear methods exhibited strong temporal and spatial consistency for both PMAD and PMHD, with linear relationships being stronger than nonlinear ones. (2) The DRTs of PMAD and PMHD were around 1–2 months and 3–5 months, respectively. Significant differences existed in the DRT between the dry season and the rainy season. (3) A divergent spatial pattern of the proportion of DRT was observed between PMAD and PMHD. (4) Significant statistical correlations between meteorological drought and agricultural drought and between meteorological drought and hydrological drought were observed in specific periods for each sub-region; (5) Hydrometeorological factors contributed the most to DRT, followed by terrain factors and the land cover types. The findings of this study deepened our understanding of the spatial–temporal relationship of multiple drought propagation types in this transboundary river basin.
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    The “slow anatomy of change”: urban knowledge trajectories towards an inclusive settlement upgrading agenda in Freetown, Sierra Leone
    (SAGE Publishing, 2022-07-28) Macarthy, Joseph Mustapha
    This paper examines the dominant knowledge paradigms that have underpinned planning over time in Freetown, Sierra Leone and their implications for urban equality. Looking at the history of the informal settlement upgrading agenda, it presents this analysis through a historical mapping, outlining the knowledge paradigms that have informed planning approaches from the colonial era to the present day. It then outlines three strategic moments over the past 13 years, in which organized informal settlement residents and wider coalitions have mobilized diverse forms of knowledge. By engaging both with long-term trajectories and the intimacy of more recent experiences, it outlines what we refer to as the “slow anatomy of change” through which diverse knowledges have been consolidated. The paper offers reflections on the temporalities and geographies of change; the role of knowledge production as a historical site of power disparities; and what these strategies tell us about the negotiation of power and knowledge through planning towards urban equality.
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    Drivers of land-use and land-cover change in rural landscapes; a case in Eastern Sierra Leone
    (Taylor & Francis, 2022-09-28) Lahai, Morrison K.
    This study provides the first attempt at assessing the drivers of LULC change in eastern Sierra Leone where settlement expansion is as eminent as the proliferation of the primary industrial sector, notably agriculture and artisanal mining. For this purpose, using Landsat images at 1986, 2000 and 2020, LULC maps of the study area were obtained. The principal drivers of LULC change were identified based on field observations and interviews with local residents. Additionally, population and climate data were obtained to better understand LULC changes. Vast changes were observed in Shrub/Fallow, Grass/Cropland, Wetland and Built/Barren. Moderate changes were observed in Trees/Forest and Open Water. The drivers of LULC change are attributable to population growth as the main underlying driver and agricultural expansion and infrastructural development as the main proximate or direct drivers. Moreover, the declining rainfall in tandem with rising temperatures can be linked to the shrinking Wetland and Open Water.
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    Assessment and Inter-Comparison of Multi-Source High Spatial Resolution Evapotranspiration Products over Lancang–Mekong River Basin, Southeast Asia
    (Multidisciplinary Digital Publishing Institute, 2022-01-20) Chen, Houbing
    Evapotranspiration (ET) plays a crucial role in water balance within the global hydrological cycle. Timely assessment of ET products can provide the scientific basis for quantitative analysis of hydrological cycle processes and water resources assessment. In this paper, four high spatial resolution remote sensing ET products—the Moderate-resolution Imaging Spectroradiometer global terrestrial evapotranspiration product (MOD16), the ET product based on Penman–Monteith–Leuning equation version 2 (PML-V2), the ET product based on the Breathing Earth System Simulator (BESS) and the ET product of the Global LAnd Surface Satellite (GLASS)—were firstly assessed using the eddy covariance (EC) of different vegetation types in the Lancang–Mekong River Basin (LMRB). To fully assess the performances of these four products, spatiotemporal inter-comparisons and literature comparisons were also conducted across different climatic zones. The results are summarized as follows: (1) MOD16 does not perform well as compared to the other three products, with its Root Mean Square Error (RMSE) being higher than GLASS, PML-V2 and BESS, which are approximately 0.47 mm/8-day, 0.66 mm/8-day, and 0.90 mm/8-day, respectively; (2) the performance of each product varies across different vegetation types, and even within the same climate zone. PML-V2 performs best in evergreen broadleaf forests, BESS performs best in deciduous broadleaf forests and croplands, and GLASS performs best in shrubs, grasslands and mixed vegetation; (3) each product can well reflect the spatial difference brought by topography, climate and vegetation over the entire basin but all four ET products do not show either a consistent temporal trend or a uniform spatial distribution; (4) ET ranges of these four products over LMRB are consistent with previous literature in evergreen broadleaf forests, deciduous broadleaf forests, needleleaf forests and mixed forests in other regions with the same climate zones, but they show great differences in croplands, grasslands and shrubs. This study will contribute to improving our understanding of these four ET products in the different climatic zones and vegetation types over LMRB.
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    Driving Factors of Infants and Under-five Children Feeding Practices in Kori Chiefdom, Sierra Leone
    (B P International (a part of SCIENCEDOMAIN International), 2023-02-04) Blango, Victoria Nancy
    **Introduction:** The degree to which mothers adhere to the recommendations of the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) regarding breastfeeding and complementary feeding is key to the nutritional status of their infants and young children and their overall development. However, the adherence to this dietary recommendation is contingent on the socio-economic conditions of the child-bearing parents, especially the mothers. This study looks at how the socioeconomic characteristics of mothers influenced the feeding practices of children not more than five years old in rural Sierra Leone. **Method:** Data were collected in 2017 on representative mothers with children within 0-5 years old. A total of 10 communities and 200 respondents were randomly covered in the Kori Chiefdom of Moyamba District, Sierra Leone. Structured questionnaires, inter-personal interaction, personal observation, and experience were all used to collect data. The data was analysed in Microsoft Excel and SPSS, and the results were displayed in simple graphs and tables. **Results:** Socioeconomic characteristics of mothers such as access to nutritional information, age, parity and educational status of mother as well as household’s monthly income had effects on some feeding practices. Mothers with better access to nutritional information did timely initiation of breastfeeding. Also, there was a positive correlation between mothers’ education and exclusive breastfeeding (r = 0.233, p < 0.01). Mother’s age and parity also have positive relations with duration of breastfeeding (r = 0.552, p < 0.01) (r = 0.191, p < 0.01). However, household’s monthly income had a negative correlation with age of introduction of the child to complementary feeding (r = -0.259, P < 0.01) and its duration a strong positive one (r = 0.202, p < 0.01) than education of the mother. Whereas, a slight negative correlation exit between the age of the mother and duration/period of complementary feeding (r = -0.206, p < 0.01). **Conclusion:** The study shed enough light on the socioeconomic characteristics and feeding practises of children in impoverished rural Sierra Leone. In this sense, the study has laid the groundwork for more in-depth correlation studies on the factors influencing children's feeding practises and how this affects the nutritional status of children in poor rural Africa. From here, practically adoptable recommendations can be advanced for the attention of the governments, public institutions, the private sector and the individuals of the society.
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    Urban Infrastructure and Transit-Oriented Development in Freetown, Sierra Leone
    (Springer Nature (Netherlands), 2024) Koroma, Braima M
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    Improving access to urban piped drinking water services in Africa: a scoping review
    (IWA Publishing, 2024-11-20) Weston, Sally L.
    Access to reliable and safe piped drinking water protects public health and provides a range of social and other benefits. There has been substantial investment across Africa to improve access to piped water supply in urban areas of Africa, but the evidence on which approaches are most effective is sparse. We undertook a scoping review to identify studies in the published and grey literature that provide evidence on projects to improve access to piped water supply in urban areas of Africa. Available evidence is sparse and concentrated in a small number of countries. While progress has been made to increase access to piped water supply, benefits to low-income populations have been lower than for high-income groups. More projects focused on physical expansion of infrastructure rather than use of financial and economic measures, despite evidence of financial barriers being important in restricting access. There was mixed evidence that expansion of services improved service quality with several instances of deteriorating services found. The narrow literature base identified in this review highlights the urgent need for rigorous studies of effective approaches, which is essential to build upon successful interventions that hold the most promise for the future.
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    Differences in drought characteristics, progression, and recession across ecosystem types in the pantropical region of the Lancang-Mekong River Basin
    (Elsevier BV, 2024-07-05) Feng, Ganlin
    Exploring the development and impacts of drought across different ecosystems can offer new insights for mitigating the adverse effects of drought events. Using the pantropical Lancang-Mekong River Basin as the study region, we investigated the agricultural, ecological, and hydrological drought characteristics and explored their drought progression and recession rates across four vegetation ecosystem types: tropical forests, subtropical forests, shrubs, and crops. We utilized newly developed drought indices based on the ERA5-Land reanalysis dataset, GOSIF chlorophyll fluorescence data, and modified Moderate Resolution Imaging Spectroradiometer (MODIS) land cover data. The results showed that agricultural and hydrological droughts exhibited increasing trends from 2001 to 2021, whereas ecological drought displayed a decreasing trend over the same period. The cropland region experienced the fewest drought events, shortest drought durations, slowest progression rates, and lowest recession rates. By contrast, the two evergreen, broadleaf forest ecosystems (subtropical and tropical forests) experienced the highest number of drought events and fastest progression and recession rates. The findings suggest a trade-off relationship between vegetation resistance and recovery, where faster drought onset is associated with faster drought recession for ecological drought. Given the more severe challenges posed by agricultural and hydrological droughts, the riparian countries in the Lancang-Mekong River Basin should adopt proactive financial and management measures to mitigate the adverse impacts of these drought types. The insights gained from this study can inform the development of targeted strategies for drought monitoring, preparedness, and response across diverse ecosystems.