Species and ecosystems are increasingly threatened by the human activities, while climate change projections show that eastern Africa may face considerable changes in temperature and rainfall regimes. These changes pose huge challenges for the prioritization and implementation of conservation and sustainable management of the natural environment. There is therefore an urgent need for information that allow us to assess the current status of the region’s natural environment and to predict how this may change under future climates. This thesis aims to improve our knowledge on natural vegetation distribution in eastern African, examine how this may change under future climates, and how this can be used to identify conservation priorities in the region. Chapter 1 presents a brief overview of the concept of the potential natural vegetation (PNV), synthesizes the general findings and discusses future perspectives. Chapter 2 presents a biogeographic study of a hitherto poorly studied vegetation type in Ethiopia which is characterized by many near-endemic or endemic species. Chapter 3 focusses on the distribution of fire and different potential vegetation types in Ethiopia under current climatic conditions and how this is likely to change under different climate change scenarios. Chapter 4 presents an environmental gap analysis to prioritize conservation efforts in eastern Africa, based on an evaluation of the environmental representativeness of protected areas and an assessment of the level of threat to the regions different vegetation types. Chapter 5 present a new approach to quickly map the distribution of species by combining species distributions from the PNV maps with that of habitat distribution models, and use this to project to what extent and where projected climate changes are likely to affect the potential distribution ranges of a range of woody species in eastern Africa.