Land Use and Land Cover Dynamics in Lower Awash Rangelands, Ethiopia

Abstract

Change detection is one of multi temporal analysis in remote sensing that is important for studying the dynamics of environment. Change detection is useful in many applications such as land use changes, habitat fragmentation, rate of deforestation, coastal change, urban sprawl, and other cumulative changes through spatial and temporal analysis techniques such as GIS and Remote Sensing along with digital image processing technique. The objective of this study was to estimate the spatiotemporal changes pertaining to land use land cover (LULC) ,the driving forces behind these changes and its impact on the biodiversity and the livelihood of pastoralists in Lower Awash Range Lands. An integrated approach utilizing remote sensing and geographic information system (GIS) was used to extract information pertaining to LULC change. Satellite images of LandSat TM 1986, LandSat ETM+ 2001 and LandSat ETM 2014) were used. In addition, individual interviews with 134 randomly selected households, discussions with focus group and key informants, and field observations were also incorporated for the study. All images were classified using object-based image classification technique. Accuracy assessments were conducted for 2014. Change analysis was carried out using post classification comparison in GIS. LULCs were successfully captured with overall accuracies 88.52% and Over all Kappa value of 0.87. When the 2014 LU/LC classification compared with 1986 LU/LC classification, there were changes that showed decrease or increase in particular land use land cover. The land use land cover categories, which showed increments are bush land, irrigation land, water body, built up area and bare land have increased by 21448.64 ha (+27.24 % ) 4665.9 ha (+43.81%) 50.87 ( + 108.93%) 8825.93ha ( +786.91% ) and 32208.8 ha ( +57.40%) respectively. On the other hand shrub land and grass land decreased by 9637.1ha (-51.67%) and 57563 ha (-94.42%) respectively. Based on the analysis, changes were observed in the spatial extent of different LULC types over a period of 30 years. Significant changes were observed in the spatial extent of bush land, bare land, shrub land, water body, residential area and irrigation land. From the study it was found that the major driving forces for these changes were population growth and drought expansion of agriculture. Drought, infrastructural development such as roads and town establishment, land tenure change from communal to private use right, Sedentary settlement expansion growing human population, increased demand for firewood and construction followed by deforestation, over grazing, State farm expansion, climate change/rainfall variability, flooding, and soil erosion are the major drivers of land use/cover change in the sub-basin. According to the survey and focus group discussion, 100% of the pastoralist, 95% of agro-pastoralist agreed on the impacts of LULC change on loss of biodiversity and ecological services of the study area. The LULCC in relation to P. juliflora invasion have intense effects on the biodiversity of the study area which in turn affect the capacity of the area to deliver ecosystem goods and services. Therefore, the existing policy framework needs to focus upon mitigating the impacts of forces (natural, economical, demographic, economical, infrastructural and political) factors responsible for LULC change so as to ensure sustainable development of land resources.