| Land use-land cover(LULC)change has occurred at all time in the past,is presently ongoing and is likely to continue in the future,Ethiopia is a country in the Eastern Horn of Africa where a significant LULC change has been occurred over the last century,due to the rapid expansion of agricultural lands at the expense of loss of forestlands particularly in highland areas of the country.This is predominantly true in the Central Rift Valley(CRV)region of Ethiopia,an area characterized with highly fragile ecosystem and subjected to both natural(e.g.,climatic and geologic)and human-induced(e.g.,LULC change)pressures.This rapid land use dynamics in CRV is further favored by its proximity to the capital city,Addis Ababa,and its huge accessible irrigation water resources in the country,which attracted both domestic and foreign agricultural investments over the last decades.Such unregulated LULC changes,in turn,has imposed several socio-environmental impacts in the region that negatively affected both human livelihood and environment currently.These problems have attracted scholarly attention specifically in terms of LULC changes,land degradation,water resources management,climate variability,and food insecurity over the last decades.Therefore,this thesis is intended to 1)detect and map the LULC change and examining the systematic and random transition dynamics at different spatiotemporal scales;2)identify the underlying drivers and proximate causes of LULC change in the study area;3)explore trends in climatic variability over the last three decades(1981-2016)and assess its resultant effect on farmers' historical land use/livelihood change;and 4)assess the socio-environmental impacts of LULC change in the study area.To achieve the objectives of this study,a combination of different methods and datasets were used.To detect and map LULC changes for 1986,2000,and 2016,remote sensingderived cloud-free Landsat imageries for respective years were processed using GIS software.Accuracy assessment was done using GCPs collected during field verification.Then,the study identified systematic and random LULC transitions that are owing to the random process of change,by comparing the map of 1986 and 2016 to produce transition matrices.LULC change drivers and impacts were identified by employing a cross-sectional survey design that involved a household interview,focus-group discussion,key informants and experts' interview,and extensive field observation.Secondary socioeconomic and biophysical data were also used to support the results of perceived drivers and impacts of LULC changes.The major socioeconomic determinants of farmers' perception to major LULC changes and its drivers were identified by applying a Multinomial and Binary Logistic Regression analysis model respectively at the household level using STATA statistical package,version 15.In addition,Chi-square test was used to see the association between different variables.The inter-seasonal/annual trend of rainfall and temperature variability was examined for the study period and each station by processing data using the climatic analysis software,INSTAT version 3.36.The major results of this study are summarized as follows:-1)Net change and swap change accounted for about 43%and 57%of total change on the landscape respectively for 1986-2016.During the first phase of the study period(1986-2000),agricultural land and dense acacia woodland had increased by 39%and 23%,whereas bare land,shrubland,marshy land,and grazing land had declined by 39%,27%,20%,and 15%,respectively.In the second period(2000-2016),grazing land and barren land had increased by 164%and 121%,whereas scattered acacia woodland,shrubland,and dense acacia woodland had declined by 54%,32%,and 27%,respectively.Similarly,during the overall study period(1986-2016),grazing land,agricultural land,and barren land had increased by 124%,42%,and 34%,whereas scattered acacia woodland,shrubland,and marshy land had declined by 52%,50%,and 31%,respectively.The conversion of both scattered acacia woodland and shrub/bushland to agricultural land and the modification of scattered acacia woodland towards bushland and grazing land were found to be systematic transitions.A significant portion of the water body has been systematically degraded to barren land due to lake water retreat,which in turn,restored to grass/grazing land through ecological succession.Besides,a systematic scattered acacia woodland restoration on abandon agricultural lands through rehabilitation activities like area closure was observed for this study;2)Based on the descending order of percentage of relative importance,population growth,fuelwood extraction,agricultural land expansion,charcoal making,climate variability/drought,and overgrazing are the top most important principal drivers of LULC changes in the study area.The logistic regression models indicated that of the eight determinant socioeconomic variables used in the analysis,family size,income,and distance to market significantly affected households' high perception to both major LULC changes and its more perceived drivers.On the other hand,only level of education and age of household heads positively and significantly(p<0.05)affected their low perception towards policy and institutional changes and access to market and infrastructure as a driver of LULC change;3)The overall coefficient of variation for rainfall was more than 35%for both the small and the main rainy seasons.Out of the 36 years considered,total rainfall of the rainy seasons showed negative anomalies for about half of these years.Cropping season rainfall started after the average time of onset for about 42%of the database years,and it ceased ahead of the average time of the stop for about 56%of these years.The number of rainy days has experienced a general decreasing trend while the number of dry spells showed a generally increasing trend since 1981.Similarly,temperature,particularly the minimum temperature,has shown an inter-annual variability and a generally increasing trend in recent years.Due to such rainfall shortage and variability,about 82%of the drought-vulnerable farmers who had been pastoralists/agro-pastoralists before three decades,are currently changed their land use to mixed farming,10%have a wish to shift to other land use options,and none of them wish to continue either as a pastoralist or agropastoralist in the future.Unfortunately,about 40%of respondents mentioned climate change,particularly drought occurrence,as the main reason to change their land use/livelihood while others(30%)ascribed the change to a shortage of land due to population growth;and 4)Based on extensive field observation,socioeconomic survey,and biophysical data analysis,main impacts of LULC change in CRV were climate change and subsequent food insecurity,soil productivity decline,land degradation and severe soil erosion,shortage of wood and livestockfeed,loss of biodiversity,and lake water retreat.In general,the overall study findings show that unregulated LULC change has continued a major threat to both the environment and livelihood sustainability in the CRV of Ethiopia.With such existing land use scenario,neither food security nor the environmental conservation strategies of the government have been achieved currently.Hence,future land use policies need to devise strategies that work on principal drivers of L ULC change to minimize its subsequent negative impacts. |
PDF Full Text Request