Impact of Selected Anthropogenic Disturbances on the Variability of Riparian Vegetation in the River Kathita Basin, Tharaka Nithi County, Kenya

The human-induced disturbances along the fragile riparian ecosystems have significant ecological disruptions, such as loss of biodiversity and ecological services rendered by the riparian vegetation. This study investigated the impact of these selected anthropogenic disturbances, specifically sand harvesting, charcoal burning, and livestock drinking bays, on the variability of the riparian vegetation in the River Kathita basin, Tharaka-Nithi County, Kenya. The study employed purposive sampling to target disturbed sites, whereas simple random sampling was used for vegetation sampling within the sites that were targeted. Three non-disturbed sites were used as control sites and were randomly sampled along a 15KM transect. Sites affected by sand harvesting, charcoal burning, and livestock grazing exhibited lower species diversity (0≥H<1.5) while undisturbed sites maintained higher diversity (1.1>H ≤2). Although the Kruskal-Wallis test for tree diversity among the sites was not statistically significant (p=0.07), for tree species richness the test was (p = 0.047). Charcoal burning sites were characterised by large tree diameters at breast height (DBH) but lower tree heights. Sand harvesting and charcoal burning sites had high diversity of seedlings and saplings in abandoned sites, indicating the ability to recover and re-establishment of vegetation in the absence of disturbance and with protection. Livestock drinking bays showed a shift in vegetation composition from grasses and shrubs to dominance by forbs and herbaceous plants. There were strong correlations between sand harvesting, charcoal burning, livestock grazing, and tree diversity, which was significant for livestock grazing (p=0.01) and marginally insignificant for sand harvesting and charcoal burning (p=0.06). The study recommends that local and national stakeholders regulate sand harvesting, charcoal production in riparian areas, and develop strategies for managing livestock access to drinking bays. Future research should explore the combined effects of climate change, agriculture, and land-use policies on riparian habitat ecosystems.