Reducing emissions from deforestation and forest degradation (REDD) is based on a core idea: reward individuals, communities, projects and countries that reduce greenhouse gas (GHG) emissions from forests. However, many difficult questions must be addressed before mechanisms that fully exploit the potential of REDD can be created: How can we measure reductions in emissions when data are poor or do not exist?; How can we raise the billions of dollars needed to put a REDD mechanism in place?; How can we make sure that any reductions in deforestation and degradation are real (additional), and..