The Diffusion of Climate Adaptation Policies: Motivations, Mechanisms, and Impacts

Diffusion has often been hypothesized as a central mechanism in enabling the spread of innovative policies. Proponents argue that the cumulative outcome of diffusion can amount to a form of bottom-up governance with substantial effects. Diffusion has been described as relevant at various governance levels, whenever specific circumstances such as a lack of resources may encourage actors to look elsewhere for solutions. This is especially the case in the emerging policy field of climate change adaptation. But what motivates policy diffusion, what mechanisms are at play, and what are its impacts? Extant theory suggests that policy diffusion may happen because of conscious efforts to learn from the successes and failures of others, because of real or perceived competition, because of coercion, or because of desires to emulate what others are doing. But what can we learn from empirical instances of adaptation policy diffusion, particularly at the local level? Which drivers of diffusion have been identified in the literature and what are their relative contributions? And to what extent do multi-level interactions help or hinder the diffusion of adaptation policies? This paper conceptually distinguishes the motivators from the mechanisms of policy diffusion, and then turns to its impacts as the third, important category. To this effect, the paper unpacks the mechanisms (emulation, competition, learning, coercion) into their component parts and assesses how they unfold in connection with other factors such as available resources, institutions, policy entrepreneurs or national and international organisations, including multi-level interactions. At the same time, it recognizes that policy diffusion can have both positive (i.e., adaptation-enhancing) and negative (i.e., adaptation-reducing) effects. Drawing on a thorough literature review, it advances the debate by assessing the state of the evidence on adaptation policy diffusion, drawing together key lessons, and identifying productive opportunities for future research.