The effects of land use / land cover change on terrestrial carbon stocks in the Manafwa Sub Catchment of Mountain Elgon

Abstract

Forests play a vital role in climate change mitigation due to their role as natural carbon sinks. However, anthropogenic activities at the expense of the natural ecosystems have caused steady changes in carbon stocks in Mount Elgon ecosystem which have not been fully understood. An assessment of the effect of Land Use/ Land Cover Change (LULCC) on Terrestrial carbon stocks in Manafwa catchment, Eastern Uganda was undertaken. The study detected spatial and temporal LULCC between 1975 and 2018; identified perceived drivers of LULCC in the catchment in the past 43 years, and further estimated the current carbon stocks as well. Analysis of satellite imagery to determine LULCC; use of tools ranging from questionnaires, focused group discussion (FGDs) guide and the logistic regression model in identification of main drivers of LULCC were used to collect data. These were supplemented by field measurements and use of allometric biomass functions to evaluate Total Carbon Stock (TCS) with various LULCC types. The study realized a sharp decline in forest cover (y = -0.0289x2 + 114.87x – 114018, R² = 0.8186) and degraded forest (y = 0.0181x2 - 72.477x + 72603, R² = 0.9449) respectively at the expense of banana - coffee (R² = 0.8039, Slope = 0.4724). In 2018, Total Carbon Stocks were high under banana – Coffee with 7.71 Mt, followed by Dense forest with 3.05 Mt and degraded forest had 0.46 Mt. This was influenced by household size, expansion of cultivated land and settlements, crops diversification, per capita disposable household income and land use policies that were of significance range of p-value 0.041 - 0.025 in the catchment.. To curb encroachment and degradation of the forest cover, the population should be encouraged to adopt better farming methods and planting of fast maturing crops and varieties of trees to harness the areas under banana-coffee, annual crops and plantation forest. The study also suggests the need for an integrated management approach of catchments to improve the net carbon storage and sequestration of the ecosystem.