Forest degradation monitoring and assessment of biomass in Harenna Buluk District, Bale Zone, Ethiopia: a geospatial perspective

Abstract

Forest is one of the major natural resources which play a vital role in maintaining the ecological balance of nature. Detection of forest degradation with remote sensing remains a challenging field of study. Over exploitation of forest resources has resulted in the depletion of the extent and quality forests resources. The present study was undertaken to monitor deforestation, forest degradation, and biomass estimation using remote sensing and GIS technology in Harenna Buluk District in Ethiopia. Supervised classification technique was applied to landsat images of 1995, 2005 and 2016. Satellite images were classified into different land-use/land-cover classes using maximum likelihood algorithm with the aid of field observations and Google Earth. Forest degradation was assessed using object-based image analysis from Sentinel-2A satellite image. Results of this study have revealed that during 1995–2005 and 2005–2016, forest and shrubland areas were decreased by 119.2 km2 (6.19%) and 12.1 km2 (0.62%), respectively. The extent of farmland, bareland, grassland, settlement and water body were increased by 99.94 km2 (5.19%), 43.11 km2 (2.24%), 75.78 km2 (3.94%), 20.54 km2 (1.06%) and 6.93 km2 (0.36%), respectively. As a result, the biomass dramatically decreased. The normalized difference vegetation index (NDVI) value decreased significantly during 1995−2016 indicating that the vegetation cover in the study area was highly disturbed. The estimated degradation during the year 2016 was 145.91 km2 (7.58%), while deforestation accounted for 171.39 km2 (8.91%) of the total study area. Thus, advanced satellite images are useful to monitor forest cover and degradation processes of natural habitats in the context of human related impacts.