This article differentiates between descriptive and explanatory factors to develop a typology and a theory of stakeholder and public engagement. The typology describes different types of public and stakeholder engagement, and the theory comprises four factors that explain much of the variation in outcomes (for the natural environment and/or for participants) between different types of engagement. First, we use a narrative literature search to develop a new typology of stakeholder and public engagement based on agency (who initiates and leads engagement) and mode of engagement (from communication to coproduction). We then propose a theory to explain the variation in outcomes from different types of engagement: (1) a number of socioeconomic, cultural, and institutional contextual factors influence the outcomes of engagement; (2) there are a number of process design factors that can increase the likelihood that engagement leads to desired outcomes, across a wide range of sociocultural, political, economic, and biophysical contexts; (3) the effectiveness of engagement is significantly influenced by power dynamics, the values of participants, and their epistemologies, that is, the way they construct knowledge and which types of knowledge they consider valid; and (4) engagement processes work differently and can lead to different outcomes when they operate over different spatial and temporal scales. We use the theoretical framework to provide practical guidance for those designing engagement processes, arguing that a theoretically informed approach to stakeholder and public engagement has the potential to markedly improve the outcomes of environmental decision-making processes.

To design effective adaptation measures to a heating climate, decision-makers need a state-of-the-art, regional and sector-specific knowledge about future climate impacts. Tailoring this information to the needs of policymakers requires collaboration between scientists and stakeholders. A lot of literature on design principles and comprehension of scientific visualisations exists. However, the links between objective comprehension, perceived usefulness for communication and aesthetics of climate change impact maps have rarely been analysed in empirical studies. In a co-design effort together with stakeholders in adaptation planning and climate change communication experts, regional climate change impact maps were developed and published as open-access dataset. The comprehension, aesthetics and perceived usefulness of different map design features were qualitatively and quantitatively evaluated in a two-step survey. Designs with less information density were understood best, found most aesthetical and useful for communication practice. Uncertainties were deemed necessary by participants, but not understood well when combined with other variables on the same map sheet. Map understanding varied significantly with the cognitive difficulty of a task. This difference was robust over user groups. Co-designing maps at the science-policy interface have the potential to create more useful and comprehensible communication materials and thus supports adaptation planning with the best available information on future climate impacts.