Explaining stated preferences for nature-based solutions for climate adaptation: A systematic mapping review of empirical evidence

Nature-based solutions (NbS) are increasingly implemented to support climate adaptation and reduce natural hazard risks. Public preferences for NbS are frequently assessed through stated preference methods, such as contingent valuation and discrete choice experiments, which elicit willingness-to-pay (WTP). However, the individual determinants shaping these preferences remain insufficiently understood. This review synthesises evidence from 90 peer-reviewed studies to examine which explanatory variables have been used to account for stated preferences for NbS and how these have been conceptualised and measured. Particular attention is given to the prevalence and predictive power of social–psychological variables, the extent of theoretical grounding in variable selection, and the operationalisation of these constructs. The findings show that both sociodemographic and social–psychological factors influence WTP. Higher income, education, and, in many cases, lower age are positively associated with WTP, while risk perception, hazard experience, environmental attitudes, and knowledge emerge as the most frequent social–psychological predictors. At the same time, the review identifies a lack of theoretical foundation, widespread reliance on ad hoc variable selection, and limited use of validated instruments, which together restrict comparability and hinder cumulative knowledge building. Addressing these shortcomings is crucial to advance empirical research and to better align NbS implementation with citizens’ values and priorities, thereby supporting more inclusive and effective climate adaptation strategies.