Participation of citizens and stakeholders in environmental governance is widely believed to enhance environmental policy outcomes. This claim has, however, been challenged both on theoretical grounds and with respect to a lack of reliable evidence. EDGE uses an evidence-based approach: By combining case survey, comparative case studies and field experimentation, the project draws on complementary methods with a high natural variety and thus external validity (case survey) and those with a higher controllability and thus higher internal validity (experimentation).Case survey: Numerous single case studies are available across Europe and North America, providing a rich, but scattered and yet untapped resource of data. A sample of c.200 cases will be precisely coded and systematically compared based on a theoretical framework that provides relevant context, process and outcome variables.A sample of around 10 comparative case studies on governance processes in the course of the implementation of the EU Water Framework Directive (WFD) will be conducted.EDGE will perform one of the first field experiments in governance research. Field experiments are highly promising, yet controversially debated and in practice challenging. Around 10 cases of ongoing local WFD implementation processes will be subject to random selection of a participatory or non-participatory governance design.Data from all three sources will be stringently analysed using the same analytical scheme. Results will be analysed with statistical and set-theoretic methods. EDGE thus aims to drastically improve the scientific knowledge on whether and under what conditions participation actually improves policy delivery in environmental governance, thus radically informing scholarly research and political practice.