In the REDD+ debate, tenure security is often linked to equity concerns. Yet REDD+ is also about the effectiveness of reducing emissions. We propose a conceptual framework linking tenure with REDD+ effectiveness, taking into account that tenure security equally protects the right to reduce and to increase emissions. Survey-based research, at five emerging REDD+ sites in Indonesia in 2010, revealed that tenure is ambiguous and contested, thus insecure. Low dependence on forest-based livelihoods suggests limited interest in reducing emissions. Securing community tenure does not necessarily lead to REDD+ effectiveness unless it can compete with other economic interests that emit GHGs.