Faculty of Science (Research Outputs)

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Start date: 2020Subject: search.filters.subject.SDG-13: Climate action

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    Spatio-temporal trends in daily precipitation extremes over the Enkangala escarpment of South Africa: 1961–2021
    (Springer, 2025-02) Abubakar, Hadisu Bello; Scholes, Mary C.; Engelbrecht, Francois A.
    The Intergovernmental Panel on Climate Change in its Sixth Assessment Report reported that increases in extreme weather events can already be detected in every region in the world. For eastern southern Africa the report provides evidence of an increasing trend in extreme precipitation events, but more research is needed to understand how this change is manifesting over regions as diverse as South Africa’s eastern escarpment and northern Mozambique. This study evaluates the trends in extreme precipitation over the Enkangala Escarpment, part of South Africa’s eastern escarpment, over the period 1961 to 2021. Daily precipitation data covering 22 stations with fewer than 10% missing values over 61 years were obtained from the South African Weather Service. A total of twelve extreme events precipitation indices were computed using the ClimPACT2 package, and a time series trend analysis was performed using the Trend Free Whitening Mann Kendal test and a field significance test. The results indicate significant increasing trends in nine out of the twelve extreme events indices that were investigated. The three indices which have shown significant decreasing trends include Consecutive Wet days (CWD) at (0.03 day/year total annual rainfall (PRCPTOT) (0.61 mm/decade) and the annual count of days when precipitation≥10 mm (R10mm) of 0.32 days/decade. Indices such Rx1 days, Rx3 days and Rx5 days exhibited increasing trends of 0.2 days/decade each. Other indices with an increasing trend are CDD (3.6 day/decade), R20mm (0.2 days/decade) and R30mm (0.2 days/decade). The R95p (11.2 mm/decade) and R99p (6.0 mm/decade) indices, and Simple Daily Intensity Index(0.4 mm/decade) also exhibit positive trends over the study period. Overall the analysis is indicative of a change in the nature of rainfall over the Enkangala escarpment of South Africa, with annual rainfall totals, the number of consecutive wet days and the frequency of events with smaller thresholds such as 10 mm/day decreasing, but with extreme events of larger thresholds occurring more frequently. That is, when it rains, it tends to rain more intensely than in the past. The use of a field significance test was useful to formalise when relatively small but spatially homogeneous trends detected at separate weather stations yield statistical significance. The findings of the paper are relevant to decision and policy in multiple of socio-economic sectors active in South Africa’s eastern escarpment.
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    The synergetic effect of drought and land use changes on Ethiopian Rift Valley Northwestern Escarpment livelihood systems
    (Springer, 2025-02) Gidey, Eskinder; Mhangara, Paidamwoyo; Nasir, Jemal; Zeleke, Tesfaye; Assefa, Engdawork; Kahsay, Shishay; Birhane, Emiru
    Climate change has significantly impacted smallholder farmers in developing countries, where most livelihoods rely on rain-fed agricultural systems. The Northwestern Escarpment of the Ethiopian Rift Valley (NEERV) is among Ethiopia’s most drought-vulnerable areas and is highly affected by land use and land cover change (LULCC). This study aimed to analyze the synergistic impacts of drought and LULCC in the three major livelihood zones (LZs) of NEERV between 1983 and 2019. The study used socioeconomic, climatic, and earth observation datasets. Utilizing a mix of socioeconomic, climatic, and earth observation datasets, this paper investigated the combined effects of these factors on three major livelihood zones: Alagie-Ofla (ALOFLZ), Tsirare catchment (TCLZ), and Raya Valley (RVLZ). The analysis revealed significant rainfall variability, with annual fluctuations between 31 and 50% and seasonal variations ranging from 39 to 99%. This variability has contributed to frequent drought occurrences, with intervals of approximately 2.13 years in ALOFLZ, 2.2 years in TCLZ, and 2.13 years in RVLZ. There has been a notable increase in cultivated and built-up areas across all zones. The study found that drought and LULCC have severely impacted agricultural productivity and local ecosystems, with the most pronounced effects observed in RVLZ, TCLZ, and ALOFLZ. The findings highlight a critical need for integrated approaches to manage and monitor the synergistic impacts of drought and LULCC. The study underscores the importance of enhancing drought and LULCC monitoring systems to improve resilience and adaptability in vulnerable regions. The research contributes to a deeper understanding of how these intertwined factors exacerbate environmental and socioeconomic challenges, offering valuable insights into policy and management strategies for mitigating their effects. Recommendations include enhancing the current drought and LULCC monitoring systems to improve predictions and mitigation efforts, thus bolstering resilience and adaptability among affected communities.