Are land-based carbon projects good for local people, biodiversity, and ecosystem services? The Climate, Community and Biodiversity Alliance (CCBA), Forest Trends, Fauna & Flora International (FFI), and the Rainforest Alliance formed an alliance with the aim of producing a user-friendly manual on how to conduct cost-effective and credible social and biodiversity impact assessment. The concepts described in this Manual will be relevant to a wide range of site-level land-based carbon activities, whether designed for compliance or voluntary markets (we believe that sub-national activities will continue to have an important role in a future REDD + architecture).