The main objective of this study is to investigate land use/cover changes since 1957 in Mandura district of Benshangul-Gumuz regional state, Ethiopia. Aerial photographs of 1957, 1982 and spot-5 image of the 2006/07 were used to generate data on land use/ cover changes. The results show that from the total land use/cover conversions, which totals 5,8403 ha of land, the share that goes to farm land constitutes 90.1 % (52,600 ha), reverine trees 8.7 % (5,082 ha), and settlements 1.2 % (721 ha). Thus, conversion to farmland has increased in an unprecedented rate in the district. In contrast, forest land has significantly declined by 5.17 % and 2.59 % in 1957 and 1982, respectively. In 2006, forest cover was almost non-existent. Similarly, land use/cover transition was high for woodlands, shrub lands, grassland with scattered trees and bare land in the study period. Between 1957 and 2006, these land use/cover types have lost a total of 58,403 ha of land. The finding indicates that the natural environment is degrading at an alarmingly rate. This has accentuated resources losses that have endangered the livelihoods of the indigenous population. The study finds population dynamics (including size, growth, migration, and urbanization) and socioeconomic, land tenure changes and haphazard decision making processes as major factors triggering these dynamic changes. Customary land tenure system has changed following the intrusion of highlanders from the neighboring region. As a result, the indigenous population has been forced to engage in extractive economic activities such as selling charcoal and firewood, activities that have never been practiced in the area in the past. This has, in turn, negatively affected the natural environment. Land use/cover alteration, which is a serious problem in highland Ethiopia, is now gradually shifting to the lowland regions of the country. Urgent attention is required to deal with this growing problem in lowland Ethiopia.