Ecosystems in a Sate of Flux: Evidence from A Kenyan Coastal Riparian Ecosystem
Riparian ecosystems are considered hotspots of carbon and nitrogen transformations. These biochemical transformations are driven by anthropogenic activities in the immediate riverine water catchments. The anthropogenic activities may include and not limited to extraction of goods such as agricultural products, wood products, honey, plant based pharmaceutical products, livestock products, firewood, water and grass for thatching homesteads. Riparian ecosystems also provide important tangible and intangible ecosystem services comprising spiritual and aesthetic functions, pollination, ecosystem detoxification functions, carbon and nitrogen sequestration and CO2 sinks for amelioration of climate change impacts among others. These ecosystems are increasingly threatened by degradation attributed to land use changes. Human perturbations such as crop farming on riparian land, overgrazing and population pressure on land resources influence degradation of riparian ecosystems, with profound effects on biodiversity conservation and local livelihoods. Evidence from the literature indicates that although there is a general understanding regarding the response of terrestrial and wetland ecosystems to human perturbations, there is a dearth of information on the response of African riparian ecosystems to ecologic and socioeconomic impacts. The purpose of this paper is to present research evidence on the response of River Lumi riparian ecosystem to ecologic and socio-economic impacts and contextualize management implications for arresting biodiversity loss. River Lumi riparian ecosystem in Taita Taveta County was stratified into three land use systems comprising livestock production, mixed crop-livestock system and pure crop production system in the upper, middle and lower reaches of the river respectively. The objective of the study was to examine the role of anthropogenic influence on riverine vegetation structure, tree species diversity soil characteristics and household livelihoods. Thirty-six belt transects were established perpendicular to the river and plots measuring 30.0m by 15.0m were designated to assess forest structure and tree species diversity. On the basis of semi-structured questionnaires, 353 households living adjacent to the riparian ecosystem were interviewed to determine the interaction between socio-economic factors and household response to degradation. Statistical testing for significance was performed at 95% confidence interval. Tree species diversity (F (1, 2) = 0.94; p=0.401)), seedling density (F (1, 2) = 0.07; p=0.937), sapling density (F (1, 2) = 0.44; p=0.647) and tree stand density (F (1, 2) = 2.23; p=0.110) were not significantly different in the three-land use production systems. However, diameter at breast height (DBH) values in the livestock production system were significantly different from those in the mixed and crop farming systems (F (1, 2) = 2.98; p=0.052). Livestock production system favoured larger tree sizes compared to the crop farming system. Soil characteristics influenced the occurrence and distribution of dominant tree species (F (1000) =7.1; p=0.001), and less dominant tree species (F (1000) =2.4; p=0. 01). Household response to degradation was influenced by gender of household head (r = 0.025; p=0.661) and household income (r = 0.016; p=0.762). Evidence from this study shows that agricultural expansion, overgrazing and human population growth have contributed to accelerated human induced transformation of riparian forest structure, biodiversity erosion and loss of critical CO2 climate change sinks associated with River Lumi riparian ecosystem. Evidence is adduced here for the need for development of a land use plan and auxiliary effective legal, policy and institutional infrastructure for effective management of riparian ecosystems.
