This document discusses measuring and governing changes in forest carbon stocks in complex landscapes. It presents an overview of the I-REDD+ project which aims to study how dependent REDD+ is on community participation in monitoring. The project is studying sites in Vietnam, China, Laos and Indonesia to evaluate the accuracy, costs and reliability of local community carbon measurement. It finds that remote sensing is limited for complex landscapes, and participatory monitoring can provide accurate and cost-effective validation while also strengthening REDD+ governance. The document concludes that participatory monitoring should be integrated into national monitoring, reporting and verification systems to help achieve REDD+ objectives.