Abstract: "This paper seeks to describe changes in land cover, land use practices, and tenure systems in several villages in northeast Cambodia over the last 50 years. The project integrated the development of a spatial database (based on 1953 and 1996 aerial photographs and 1:50,000 base maps) with socioeconomic information collected for a development project, and an analysis of relevant socioeconomic policies. Over the last half-century, land use and total tree cover have remained stable, but fragmentation of the tree cover has increased extensively. Land use has begun to change recently as both Cambodian and foreign investors invest in industrial agricultural crops such as palm oil, rubber, cassava, and kapok. In the past, farmers had a clear sense of village lands, but specific boundaries between villages were not traditionally required. This study suggests that national land tenure policies are making it increasingly difficult for farmers to maintain their traditional swidden land use practices. Simultaneously, market pressures -- the commercialization of subsistence resources and the substitution of commercial crops for subsistence crops -- are encouraging farmers to engage in new and different forms of commercial agriculture. Combined, these forces will eventually cause a major change in land use practices from swidden agriculture to commercial crops, and a change in land cover from secondary vegetation to monocultural agriculture. These changes have significant implications for biodiversity, watershed hydrology, and carbon sequestration, as well as the lives and livelihoods of local people".....Keywords: participatory assessment, swidden agriculture, land use transitions, aerial photography