Using a significant amount of public funding, large-scale nature-conservation projects in Germany aim to secure and develop ecologically valuable areas and endangered habitats and species. Due to the substantial land-use changes accompanying these projects, their implementation can also have relevant climate effects – one result which has not been explicitly focused upon previously. Our study analyses major cost positions in implementing such projects, particularly the expense of changing or abandoning agricultural land-use for conservation purposes. We link public funding to relevant climate effects and derive CO2 abatement costs. Therefore we conduct plot-specific ex-post analyses of agricultural land-use and greenhouse-gas (GHG) emissions. Our study takes place in regions where changes in agricultural land-use for conservation purposes have been fully implemented in the past and where climate effects are expected to be high. Our analysis is based on data provided by regional stakeholders and our project partners. First results show that land-use changes for conservation purposes can lead to positive climate effects. The efficiency as regards “abatement costs” we derive on basis of the data set available lies within the range of costs for alternative measures of climate change mitigation. However it becomes clear that CO2 abatement cannot be seen as the only benefit of such measures; the high cost of agricultural compensation has to be contrasted with further effects such as biodiversity and water conservation