Background
The Ethiopian highlands have experienced intense levels of land use dynamics and forest cover transformations over the past few decades. Multiple socio-economic, demographic and bio-physical factors have driven such transformations. Nevertheless, recent expansion of urban settlements and infrastructural development could have accelerated the rate at which land cover transformations preceded but little is known about their impacts on land cover transformations in the vicinity of Addis Ababa, Ethiopia. This study, therefore, focuses on detecting long term dynamics of land use/land cover (LULC) change since the 1950s and current state of forest susceptibility to degradation in North-eastern Addis Ababa, Ethiopia. In this study Panchromatic Aerial photographs (1957), MSS (1975), TM (1995) and Sentinel-2 (2017) images were used to generate LULC types. We employed object-based classification techniques to generate LULC types for 1957 aerial photographs and maximum likelihood algorithm for images of 1975, 1995 and 2017. We also generated forest degradation susceptibility map for the study area by employing a multi-criteria approach on the ArcGIS analysis platform.
Results
Over the course of 60 years (1957–2017) the extent and direction of LULC have become more dynamic. Agricultural land and forest land showed a comparably equal extent of net change (+ 36.7% and − 37.8%, respectively) but to opposite directions. Forest lost 25.1% and 18.7% of its cover to barren land and agricultural land, respectively. The net change for forest was negative except for the period 1975–1995, with varying rates of deforestation during the four distinct study periods. However, a heightened level of deforestation occurred after the mid-1990s due to rapid urban growth and a change in government economic policy. A 6.2% net change of urban/settlement served as a catalyst for LULC transformations in the last two decades. Our findings also revealed that 97.2% of forests were located at a radius of 1 km distance from urban centers and settlements whereas 92% of them were accessible by road networks of a km radius. Similarly, 71% of forests suffer from edge effects while biophysical factors such as streams as vectors of disturbance and slopes expose about 35% of forests to degradation.
Conclusion
Over the last six decades the study area has shown an unprecedented level of LULC change. The main drivers of change were the combination of bio-physical processes especially drought cycles, demographic dynamics (population growth, density and internal migration), urbanization and successive government development policies. The massive conversion of forests to agricultural land and barren land in the study area will have far reaching impact on biodiversity and ecosystem services, land degradation and a change in local hydrological regime.
