Assessing the effects of land use/ cover change on the carbon stocks in Kaliro District, Eastern Uganda

Abstract

In Kaliro District, anecdotal evidence suggests that land use/ cover has been changing very fast with implications on woody biomass. It is also believed that Kaliro District has suffered major deforestation and degradation of fragile ecosystems in the past decades as a result of natural and human induced drivers that have triggered changes in land use/ cover, however, there seems to be inadequate quantitative information to this effect. Therefore, this study sought to fill the aforementioned information gap that can be used as a leverage to conserve, restore and ensure wise use of the natural resources in Kaliro District. This study assessed land use/ cover changes over a period of 30 years (1987 to 2017) in Kaliro District. In addition, the study also assessed both the drivers of land use/ cover changes and the above-ground woody biomass and below-ground carbon stocks of the different land use/ cover classes. Landsat satellite images (30m) were analyzed at an interval of 10 years using GIS software to obtain the coverages of the land use/ cover classes and their change in Kaliro District. The drivers of land use/ cover changes were assessed through satellite image analysis while the biomass and carbon stocks of different land uses were assessed through tree measurements and soil analysis. The results revealed nine land use/ cover classes as existing in the district, namely wetlands, bushlands, subsistence farmlands, commercial farmlands, built-up areas, thickets and shrubs, open water, tree plantations and natural forests. Wetlands, bush lands, open water and forests were observed to be decreasing in size respectively in the last 30 years in correspondence with subsistence farmlands that were found to be increasing in size in the same period. The drivers of land use/ cover changes were categorised into four classes, namely: social drivers (household size, land tenure system, level of education of the households); economic drivers (agriculture, poverty, industrialization and charcoal production), political drivers (weak laws, weak enforcement institutions and political stability); and environmental drivers (desertification, invasive pests, floods, among others). The economic drivers (most especially agriculture expansion and poverty) were the most influential drivers of the land use/ cover changes and these were followed by social, political and environmental drivers. Forests had the highest biomass per hectare (85.68ton/ha), followed by tree plantations (67.41 ton/ha), then built-up areas (13.0 ton/ha), small scale farmlands (11.50 ton/ha) and commercial farmlands (0.89 ton/ha). 53.5% of the Below-ground plot carbon stock was in the 0-15cm soil depth and 46.5% of the below-ground plot carbon stock was in the 15-30cm soil depth. The Below-ground carbon stocks distribution per plot was in the order wetlands>subsistence farmlands>commercial farmlands>bushlands>built-up>tree plantations>thickets and shrubs>open water. Below-ground carbon stocks were generally decreasing in wetlands, forests and built-up areas in that order from 1987 to 2017, while that for subsistence farm lands was increasing at a small rate. The Below-ground carbon stocks for other land use/ cover class was almost constant at zero. Land use/cover in Kaliro District has been changing very fast under the influence of anthropogenic factors, mainly agriculture, poverty and population growth, and this has greatly affected the biomass and carbon stocks in the District. It is recommended that environmental awareness about the proliferating land use/ cover changes is undertaken, afforestation and agroforestry are increasingly done, degraded wetlands are restored and environmental legislations are enforced.