Browsing by Author "Dube Timothy"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Land use and land cover changes in sub-catchments of Zimbabwe and their implications on wetland and catchment soil water conditions
    (Elsevier Ltd, 2025) Dube Timothy; Mupepi Oshneck; Marambanyika Thomas
    This study evaluated land use and land cover changes in the Shashe and Tugwi and Zibagwe sub-catchments from 2017 to 2023, with a focus on their impacts on dry season wetland extent and condition. Utilizing the Google Earth Engine Cloud Computing platform, Sentinel-2 Level 1C data were processed using Support Vector Machine (SVM) classification algorithm to analyse these changes. The Soil Moisture Active Passive level 4 (SMAP L4) soil moisture and the Normalised Difference Vegetation Index (NDVI) were computed to determine the influence of catchment level land cover change on soil moisture conditions. This study considered the influence of land cover on wetland conditions and catchment level soil moisture levels which got minimum attention in previous wetland studies. The study highlights that bare land in Tugwi and Zibagwe increased more rapidly (601.1 %) than in the drier Shashe sub-catchment. However, the wetland area decreased more in Shashe, indicating greater wetland degradation despite the slight difference (0.4 %). The analysis revealed that wetlands experienced an overall 11.8 % loss in Shashe and 11.4 % loss in Tugwi-Zibagwe. Results indicate that 5.2 %, 3.4 % and 2.3 % of the wetland area was replaced by grassland, shrubland and bare land respectively in Tugwi and Zibagwe combined whilst 4.8 %, 3.6 % and 2.32 % of the wetland area were replaced by bare land, grassland and shrubland respectively in Shashe. Statistically significant weak positive correlations were confirmed between soil moisture and NDVI in Tugwi and Zibagwe combined (r = 0.28; p = 0.04) and Shashe (r = 0.43; p = 0.02). Rainfall had stronger correlation with soil moisture in Tugwi and Zibagwe (r = 0.43; p = 0.19) and Shashe (r = 0.62; p = 0.38) which were not statistically significant indicating more influence of land cover on soil moisture than rainfall. The findings accentuate the critical need for sustainable land use practices to mitigate the adverse effects on natural land cover and wetland ecosystems. The rapid expansion of bare land and reduction in wetlands underscore the pressing challenges posed by land cover changes, particularly in regions experiencing increasing aridity. •Land use and cover changes in the three sub-catchments are assessed.•The influence of land cover change on wetland extent and soil moisture conditions are analysed.•The relationship between root zone soil moisture and rainfall and land cover change is analysed.
  • Thumbnail Image
    Item
    National-scale spatiotemporal patterns of vegetation fire occurrences using MODIS satellite data
    (PubMed, 2024) Dube Timothy; Upenyu Naume Mupfiga; Onisimo Mutanga
    As the risk of climate change increases, robust fire monitoring methods become critical for fire management purposes. National-scale spatiotemporal patterns of the fires and how they relate to vegetation and environmental conditions are not well understood in Zimbabwe. This paper presents a spatially explicit method combining satellite data and spatial statistics in detecting spatiotemporal patterns of fires in Zimbabwe. The Emerging Hot Spot Analysis method was utilized to detect statistically significant spatiotemporal patterns of fire occurrence between the years 2002 and 2021. Statistical analysis was done to determine the association between the spatiotemporal patterns and some environmental variables such as topography, land cover, land use, ecoregions and precipitation. The highest number of fires occurred in September, coinciding with Zimbabwe’s observed fire season. The number of fires significantly varied among seasons, with the hot and dry season (August to October) recording the highest fire counts. Additionally, although June, July and November are not part of the official fire season in Zimbabwe, the fire counts recorded for these months were relatively high. This new information has therefore shown the need for revision of the fire season in Zimbabwe. The northern regions were characterized by persistent, oscillating, diminishing and historical spatiotemporal fire hotspots. Agroecological regions IIa and IIb and the Southern Miombo bushveld ecoregion were the most fire-prone areas. The research findings also revealed new critical information about the spatiotemporal fire patterns in various terrestrial ecoregions, land cover, land use, precipitation and topography and highlighted potential areas for effective fire management strategies.