The soft channels of policy diffusion: Insights from local climate change adaptation policy

Abstract Diffusion has become both an important concept for studying policy spread and a popular governance approach, particularly where direct coercion is unavailable or undesirable. However, the prevailing mechanism‐centered concept is difficult to measure and poorly captures the governance potential of policy diffusion. To address these issues, this article presents a new channel‐centered framework that distinguishes between six soft policy diffusion channels: autonomous, collaborative, exemplary, persuasive, organized, and funded diffusion. The framework is probed by studying local climate change adaptation policy using original survey data collected from the administrations of 190 municipalities located in the central German state of Hessen. The regression results indicate that the local institutionalization of adaptation in Hessen is associated with several interventions by higher levels of government, including the provision of a policy model, a municipal climate network, and grant programs. However, the density of concrete adaptation measures is associated with noninstitutionalized exchanges between municipalities. External grants are also found to be more effective in institutionalizing adaptation in larger municipalities. These results demonstrate the usefulness of the framework for distinguishing and comparing different diffusion channels and suggest that different types of interventions may be required to effectively support adaptation policy development at the local level.