Browsing by Author "Lejju, Julius"

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    Aquatic ecosystem changes in a global biodiversity hotspot: Evidence from the Albertine Rift, central Africa
    (Journal of Biogeography, 2019) McGlynn, Gayle; Lejju, Julius; Dalton, Catherine; Mooney, Scott D.; Rose, Neil L.; Tompkins, Adrian M.; Bannister, Wayne; Tan, Zu D.; Zheng, Xianglin; Rühland, Katherine M.; Taylor, David
    Determine the extent to which remote, high‐altitude (Afroalpine) aquatic ecosystems in tropical Africa have been impacted by global and regional‐scale environmental change processes. Location: Two volcanic crater lakes (Bisoke and Muhavura) in the Afroalpine zone, Albertine (Western) Rift, central Africa. Methods: Sediment cores were collected from Bisoke and Muhavura lakes and dated using radiometric techniques. A range of sediment‐based proxies was extracted from the cores and quantified. Sedimentary data were subjected to statistical analyses that contributed to the identification of influential environmental variables and their effects on diatom assemblages, the determination of variations in spatial beta diversity and estimates of the rate of compositional turnover over the last c. 1,200 years. Results: Sediments from the two sites provide evidence of the sensitivity of remote, Afroalpine aquatic ecosystems to perturbation. Climate variability has been a major driver of ecological change, particularly at Bisoke Lake, throughout the c. 1,200‐ year‐long record, while Muhavura Lake has been directly impacted by and recovered from at least one volcanic eruption during this time. The effects of climatic warming from the mid‐ to late 19th century and especially from the late 20th century, possibly accentuated by atmospheric deposition‐driven nutrient enrichment, appear increasingly in lockstep. Effects include changes in diatom community composition, increased productivity and compositional turnover, and biotic homogenization (reduced spatial beta diversity) between the two sites. Main conclusions: The two Afroalpine sites record changes in atmospheric conditions and their effects on diatom assemblage composition, particularly over the last c. 150 years. Drivers of these changes have the potential to disrupt ecosystems at lower altitudes in the Albertine Rift, including biodiverse areas of forest, and across tropical Africa more widely.
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    Historical Perspectives of Land Use and Land Cover Change in the Sanga-Lake Mburo former Pastoral Rangeland Ecosystem, Uganda
    (International Journal of Environment and Geoinformatics, 2022) Murithi Njagi, Shadrack; Lejju, Julius; Nkurununugi, John Bosco
    Socioeconomic, political, and policy decisions by the government may influence the socioecological changes of the land use and land cover pattern for rangeland people over time. This paper examines the historical political, policy, and socioeconomic decisions that influenced land use and land cover changes in the former pastoral community in Sanga-Lake Mburo Rangeland Ecosystem in South Western Uganda. Data on historical events were documented from literature and supplemented by an opportunistic discussion with Sanga residents. Data on land use and cover change detection between 1987 and 2020 were provided by Landsat 5 TM and Landsat 8 OLI/TIRS images and from field observations. Images were processed using QGIS version 3.20.1 employing a semi-automatic classification plugin. Political decisions and government policies related to land tenure and reforms, socioeconomics, and demographic changes were noted as underlying drivers of land use and cover changes. The overall accuracies for classified maps of 1987 and 2020 were 80.36% and 89.81%, respectively. Notably, woodland cover in the protected area increased by 170.53% between 1987 and 2020, while built-up areas and farmland increased 1348.15% and 405.03%, respectively. In the same period, wetland cover in protected and unprotected decreased immensely by 46.06%. Bareland in the park decreased by 23%, while outside the park, it increased by 25.07%. This study concludes that land use and land cover change resulted from sociocultural changes, political and policy decisions on ranches, park management, and land tenure restructuring.