Given inadequate budgets with which to stem the rapid destruction of biodiversity, conservationists must set clear priorities for action. Systematic Conservation Planning (SCP) is an approach that uses spatially explicit data to identify areas that meet conservation targets efficiently, usually focusing on species’ representation. Only rarely is the long-term persistence of species taken into account and the costs of conservation are usually ignored. I use the Eastern Arc Mountains of Tanzania as a study area to develop novel methods for creating and integrating the necessary data to fill these gaps in a developing country context. These mountains exhibit exceptional biodiversity but are also highly imperilled. I describe the biological data that I assembled for use in a series of SCP analyses. Fine-scale distribution models for species were mapped for over 500 animal and plant species of conservation concern. I then mapped Ecological and Evolutionary Processes (EEPs), which are crucial to species’ persistence and contribute to healthy ecosystem functioning. My analyses show how the inclusion of biological processes can significantly alter priorities when compared to prioritisation using information on species’ presence alone. Despite their importance, EEPs are often excluded from SCP. This is largely due to the difficulties involved in expressing them quantitatively and in optimising reserve networks to represent them at a minimum cost. This reluctance should be challenged, otherwise reserve networks will, over time, lose those elements of biodiversity that they were established to conserve. I also investigate conservation costs. Despite chronic underfunding for conservation and the recognition that funds must be invested wisely, few data on the costs of conservation are available at the spatial scales needed to inform local site management. I present methods for estimating and mapping protected area management costs, wildlife damage cost and the opportunity costs of conservation. Costs are highest in densely populated and cultivated areas, particularly in the north, whereas large areas of the more remote mountain blocs in the south show lower costs. Integrating these data into SCP demonstrates that using real cost data (rather than assuming that cost per unit area is homogenous) alters priorities and increases the efficiency of conservation within the Eastern Arc. Importantly, the efficiency savings realised through using cost, rather than area, to prioritise conservation efforts were found to be most pronounced when budgets were limited so that not all conservation targets could be met.