Collaborative environmental governance and the participation of citizens and stakeholders in public environmental decision-making is increasingly promoted on the basis that it can improve environmental outcomes relative to traditional, top-down decision-making. At the same time, it is also recognized that participatory approaches may have unintended negative environmental outcomes. As different fields of study have contributed a variety of claims as to the relationship between participation and the environment, the existing literature – while substantial – tends to be weak on causal mechanisms, and gives rise to several logical contradictions.

This paper seeks to distil causal assumptions from the existing literature, and integrate them into a consistent framework of testable hypotheses. We incorporate claims from fields such as political science, public administration, legal studies, social psychology, environmental studies, decision science, mediation and conflict resolution. We present a causal framework in the form of clusters of what have emerged as core hypotheses from the literature. These hypotheses address the relationship between participation and (a) the environmental standard (quality) of outputs, and (b) the implementation of outputs (i.e. the effect of participation on environmental outcomes and impacts). We disaggregate these hypotheses as far as possible, with the aim of isolating causal relations between important variables in the policy process such as participation and acceptance, knowledge, deliberation etc. We explore the main causal mechanisms between these variables, and locate relevant context variables such as conditioning and process factors, teasing out the often implicit assumptions on which each hypothesis is built. This way, we not only spell out and clarify the hypothesized causal mechanisms between participation and environmental outcomes and impacts, but also identify conditions under which participation may lead to better (or worse) environmental outcomes.

We argue that identification of the most important hypotheses on the relationship between participation and effectiveness is an important first step in generating and consolidating robust evidence on the ‘instrumental’ value of participatory modes of environmental governance. Such evidence should be of relevance to a wide range of researchers in the field of participatory governance, and of practical use to those that must balance environmental and democratic imperatives in designing environmental policy and conducting participatory governance processes.