Governance and the Potential Supply of Avoided Emissions. Countries with mangroves differ considerably in governing institutions and the corresponding political, economic, and social risks and barriers associated with long-term conservation projects. Implementing offsets in certain counties may require investments in management and institutional change above and beyond the opportunity cost of avoided land conversion. It is also plausible that countries with problematic management and institutional environments could be effectively excluded from the market because of the costs associated with these risks and barriers. The magnitude of such costs is difficult to estimate and beyond the scope of this analysis. However, we use the World Bank index on governance effectiveness (25) to shed light on the potential impact of such considerations on the supply of carbon offsets. For illustration, we consider two cases that limit the potential supply of offsets to countries in the top 50th or 90th percentile of the governance index (SI Appendix)