Impact of Selected Anthropogenic Disturbances on the Variability of Riparian Vegetation in the River Kathita Basin, Tharaka Nithi County, Kenya
Abstract
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.
Downloads
References
Aabeyir, R., Adu-Bredu, S., Agyare, W. A., & Weir, M. J. (2020). Allometric models for estimating aboveground biomass in the tropical woodlands of Ghana, West Africa. Forest Ecosystems, 7(1), 1-23. https://doi.org/10.1186/s40663-020-00234-9
Abebe, B., Ashagrie, M., & Eshete, G. (2024). Effects of livestock grazing on herbaceous species composition and biomass in the Simien Mountains National Park, Ethiopia. Israel Journal of Ecology and Evolution. https://doi.org/10.1163/22244662-bja10087
Ako, T. A., Onoduku, U. S., Oke, S. A., Essien, B. I., Idris, F. N., Umar, A. N., & Ahmed, A. A. (2014). Environmental effects of sand and gravel mining on land and soil in Luku, Minna, Niger State, North Central Nigeria.
Ashraf, M. A., Maah, M. J., Yusoff, I., Wajid, A., & Mahmood, K. (2011). Sand mining effects, causes and concerns: A case study from Bestari Jaya, Selangor, Peninsular Malaysia. Scientific Research and Essays, 6(6), 1216-1231.
Bellows, B. C. (2003). Managed grazing in riparian areas. ATTRA.
Chaichi, M. R., Saravi, M. M., & Malekian, A. R. A. S. H. (2005). Effects of livestock trampling on soil physical properties and vegetation cover (case study: Lar Rangeland, Iran). Int. J. Agric. Biol, 7, 904-908.
Colón, S. M., & Lugo, A. E. (2006). Recovery of a subtropical dry forest after abandonment of different land uses. Biotropica: The Journal of Biology and Conservation, 38(3), 354-364. https://doi.org/10.1111/j.1744-7429.2006.00158.x
Dharani, N. (2011). Field guide to common trees & shrubs of East Africa. Penguin Random House South Africa.
FAO. (2010). What Woodfuels Can Do to Mitigate Climate Change. FAO Forestry Paper 162. Rome, Italy: Food and Agriculture Organization of the UN.
Garbin, M. L., Misaki, F., Ferreira, P. F., Guidoni-Martins, K. G., Soares, R. B., Mariotte, P., & Silva, A. G. (2018). Long-term regeneration of a tropical plant community after sand mining. Ecology and Evolution, 8(11), 5712-5723. https://doi.org/10.1002/ece3.4127
Gebremedhn, H. H., Ndiaye, O., Mensah, S., Fassinou, C., Taugourdeau, S., Tagesson, T., & Salgado, P. (2023). Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel. Ecological Processes, 12(1), 54. https://doi.org/10.1186/s13717-023-00454-9
Jones, A. M., Kane, J. M., Engber, E. A., Martorano, C. A., & Gibson, J. (2023). Extreme wildfire supersedes long-term fuel treatment influences on fuel and vegetation in chaparral ecosystems of northern California, USA. Fire Ecology, 19(1), 28. https://doi.org/10.1186/s42408-023-00128-9
Kalema, V. N., & Witkowski, E. T. F. (2012). Land-use impacts on woody plant density and diversity in an African savanna charcoal production region. International Journal of Biodiversity Science, Ecosystem Services & Management, 8(3), 231–247. https://doi.org/10.1080/21513732.2012.681070
Kariuki, P. M. (2002). An assessment of impact of charcoal making on distribution of some tree species in Kibwezi Division (Master’s thesis, Kenyatta University). Retrieved from Kenyatta University Repository.
Kershner, J. L., Archer, E. K., Coles-Ritchie, M., Cowley, E. R., Henderson, R. C., Kratz, K., Quimby, C. M., Turner, D. L., Ulmer, L. C., & Vinson, M. R. (2004). Guide to effective monitoring of aquatic and riparian resources (Gen. Tech. Rep. RMRS-GTR-121). U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. https://doi.org/10.2737/RMRS-GTR-121
Kirema, M. M. (2020). Effects of land use changes on Thanantu River, Tharaka North Sub County, Tharaka-Nithi County.
Kiruki, H. M., van der Zanden, E. H., Gikuma-Njuru, P., & Verburg, P. H. (2017). The effect of charcoal production and other land uses on diversity, structure and regeneration of woodlands in a semi-arid area in Kenya. Forest Ecology and Management, 391, 282-295. https://doi.org/10.1016/j.foreco.2017.02.022
Kondolf, G. M., Piégay, H., & Landon, N. (2007). Changes in the riparian zone of the lower Eygues River, France, since 1830. Landscape Ecology, 22(3), 367-384.
Kori, E., & Mathada, H. (2012). An assessment of environmental impacts of sand and gravel mining in Nzhelele Valley, Limpopo Province, South Africa. In 3rd international conference on biology, environment and chemistry. IACSIT Press, Singapore (Vol. 46, No. 29, pp. 137-141).
Kouami, K., Yaovi, N., & Honan, A. (2009). Impact of charcoal production on woody plant species in West Africa: A case study in Togo. Scientific Research and Essay, 4(9), 881-893.
Kyalo, W. D. (2009). Impact of policy and socioeconomic factors on spatial distribution of livestock production systems in River Njoro Watershed, Kenya (Doctoral dissertation, Egerton University). Retrieved from Egerton University Repository.
Majumdar, A., & Avishek, K. (2023). Riparian zone assessment and management: An integrated review using geospatial technology. Water, Air, & Soil Pollution, 234(5), 319. https://doi.org/10.1007/s11270-023-06329-1
Malimbwi, R. E., Zahabu, E., Monela, G. C., Misana, S., Jambiya, G. C., & Mchome, B. (2005). Charcoal potential of miombo woodlands at Kitulangalo, Tanzania. Journal of Tropical Forest Science, 197-210.
Masunga, G. S., Moe, S. R., & Pelekekae, B. (2013). Fire and Grazing Change Herbaceous Species Composition and Reduce Beta Diversity in the Kalahari Sand System. Ecosystems, 16(2), 252-268. https://doi.org/10.1007/s10021-012-9611-6
Mathewos, M., Sisay, A., & Berhanu, Y. (2023). Grazing intensity effects on rangeland condition and tree diversity in Afar, northeastern Ethiopia. Heliyon, 9(11). https://doi.org/10.1016/j.heliyon.2023.e12345
Maundu, P., Ngugi, G., & Karanja, N. (2005). Useful trees and shrubs of Kenya. World Agroforestry Centre.
Mohammed, I. B., Okechuku, M., & Okindele, M. D. (2022). Environmental Impact of Sand Harvesting in Niger State, Nigeria. African Journal of Emerging Issues, 4(1), 18-26.
Muñoz Mazón, M., Klanderud, K., & Sheil, D. (2022). Canopy openness modifies tree seedling distributions along a tropical forest elevation gradient. Oikos, 2022(11), e09205. https://doi.org/10.1111/oik.09205
Musau, E. M., Mukiri, J., Nzogela, B., Paul, B. K., & Notenbaert, A. M. O. (2021). Assessing the environmental impacts of smallholder dairy intensification through improved feeding strategies in the Southern Highlands of Tanzania. Agricultural Systems, 191, 103137. https://doi.org/10.1016/j.agsy.2021.103137
Nasare, L. I., Opoku, S. A., Amponsah, A., Tom-Dery, D., Asante, W. J., & Baatuuwie, B. N. (2023). Effect of sand mining on riparian landcover transformation in Dallung-Kukou catchment of the White Volta basin, Ghana. Heliyon, 9(8). https://doi.org/10.1016/j.heliyon.2023.e12345
Ndegwa, G. M., Nehren, U., Grüninger, F., Iiyama, M., & Anhuf, D. (2016). Charcoal production through selective logging leads to degradation of dry woodlands: A case study from Mutomo District, Kenya. Journal of Arid Land, 8, 618-631. https://doi.org/10.1007/s40333-016-0045-9.
Okach, D. O., Ondier, J. O., Rambold, G., Tenhunen, J., Huwe, B., Jung, E. Y., & Otieno, D. O. (2019). Interaction of livestock grazing and rainfall manipulation enhances herbaceous species diversity and aboveground biomass in a humid savanna. Journal of Plant Research, 132(3), 345-358. https://doi.org/10.1007/s10265-019-01105-x
Oyoo, E. (2021). Sustainable Moderation of Sand Harvesting Effects and Conservation on Land Cover, Flora and Fauna along the Riparian Land. http://repository.rongovarsity.ac.ke/handle/123456789/2302
Sapkota, R. P., Stahl, P. D., & Norton, U. (2019). Anthropogenic disturbances shift diameter distribution of woody plant species in Shorea robusta Gaertn.(Sal) mixed forests of Nepal. Journal of Asia-Pacific Biodiversity, 12(1), 115-128.sap
Schmidt, M., Mölder, A., Schönfelder, E., Engel, F., & Fortmann-Valtink, W. (2016). Charcoal kiln sites, associated landscape attributes and historic forest conditions: DTM-based investigations in Hesse (Germany). Forest Ecosystems, 3, 1-16. https://doi.org/10.1186/s40663-016-0071-1
Schulz, K., Guschal, M., Kowarik, I., Silva de Almeida‐Cortez, J., Valadares de Sá Barreto Sampaio, E., & Cierjacks, A. (2019). Grazing reduces plant species diversity of Caatinga dry forests in northeastern Brazil. Applied Vegetation Science, 22(2), 348-359. https://doi.org/10.1111/avsc.12434
Smith, A. G., Newingham, B. A., Hudak, A. T., & Bright, B. C. (2019). Got shrubs? Precipitation mediates long-term shrub and introduced grass dynamics in chaparral communities after fire. Fire Ecology, 15, 1-16. https://doi.org/10.1186/s42408-019-0034-5
Smith, R. W., Statham, M., Norton, T. W., Rawnsley, R. P., Statham, H. L., Gracie, A. J., & Donaghy, D. J. (2012). Effects of wildlife grazing on the production, ground cover and plant species composition of an established perennial pasture in the Midlands region, Tasmania. Wildlife Research, 39(2), 123-136. https://doi.org/10.1071/WR11120
Spicer, M. E., Radhamoni, H. V. N., Duguid, M. C., Queenborough, S. A., & Comita, L. S. (2022). Herbaceous plant diversity in forest ecosystems: Patterns, mechanisms, and threats. Plant Ecology, 223(2), 117-129. https://doi.org/10.1007/s11258-022-01200-5
Stephan, K., Miller, M., & Dickinson, M. B. (2010). First-Order Fire Effects on Herbs and Shrubs: Present Knowledge and Process Modeling Needs. Fire Ecology, 6(1), 95-114. https://doi.org/10.4996/fireecology.0601095
Török, P., Lindborg, R., Eldridge, D., & Pakeman, R. (2024). Grazing effects on vegetation: Biodiversity, management, and restoration. Applied Vegetation Science, 27(3), e12794. https://doi.org/10.1111/avsc.12794
Wadud, A. I., Bugalho, M. N., & Vaz, P. G. (2024). Meta-analysis of livestock effects on tree regeneration in oak agroforestry systems. Journal of Environmental Management, 364, 121498. https://doi.org/10.1016/j.jenvman.2023.121498
Xu, M. Y., Xie, F., & Wang, K. (2014). Response of vegetation and soil carbon and nitrogen storage to grazing intensity in semi-arid grasslands in the agro-pastoral zone of northern China. PLoS One, 9(5), e96604. https://doi.org/10.1371/journal.pone.0096604
Zhang, L., Liu, W., & Ma, Y. (2020). Effects of meteorology and soil on the herb species diversity in plantations in a reclamation area of coal mine after 6 years. Journal of Environmental Management, 264, 110455. https://doi.org/10.1016/j.jenvman.2020.110455
Zhang, M., Delgado-Baquerizo, M., Li, G., Isbell, F., Wang, Y., Hautier, Y., & Wang, L. (2023). Experimental impacts of grazing on grassland biodiversity and function are explained by aridity. Nature Communications, 14(1), 5040. https://doi.org/10.1038/s41467-023-50640-5
Zhao, Y., Zhang, P., Hu, Y., & Huang, L. (2015). Effects of Re-vegetation on Herbaceous Species Composition and Biological Soil Crusts Development in a Coal Mine Dumping Site. Environmental Management, 57(2), 298-307. https://doi.org/10.1007/s00267-015-0607-91
Copyright (c) 2025 Denis Kibaara Mugambi, Rithaa Jafford Njeru, Agatha Nthenge
This work is licensed under a Creative Commons Attribution 4.0 International License.
