The effect of land use/cover change on biomass Stock in dryland areas of Eastern Uganda. A case study of Olio Sub-county in Soroti District

Drylands occupy 44% of Uganda’s land surface and provide livelihood to a cross-section of both rural and urban folks. However in the face of population pressure, drylands are increasingly in the path of conversion and degradation. This study therefore, performed an assessment of the effect of land use/cover change on biomass stock in olio sub-county from 1973 to 2001. A series of systematically corrected Orthorectified Landsat imageries of 1973, 1986 and 2001 obtained from the Landsat website were used. The images were analysed using unsupervised approach in Integrated Land and Water Information System version 3.3 and validated using field observations and historic memories of village elders. Findings indicate that land use/cover change is driven by small-scale farming. Between 1973-1986 significant declines were identified among small-scale farming (23.2%), grasslands (8.7%) and large scale-farming (9.9%). Further, declines were also registered between 1986-2001 in Bushland (12.1%), woodlands (13.9%) and wetlands (8.2%) while dramatic gains were registered in small-scale farming by 19.4%. These declines led to losses in the available biomass stock by 2001 within bushlands, wetlands and woodlands loosing 29.1 million tons, 669.1 metric tons and 87.3 million tons respectively. We conclude that small-scale farming by resource poor farmers is rapidly transforming the vegetation landscape. Therefore, there is need for increased use of remote sensing and GIS to quantify change patterns at local scales for essential monitoring and assessment of land use and or/cover change effects and human interference on the landscape.