Mapping the causality of interacting perceptions for nature-based solution and sludge treatment reed bed: A causal loop diagram in Iceland

•The perceptions of NBS stakeholders were obtained via semi-structured interviews.•A hybrid thematic analysis including deductive and inductive was conducted to mine codes.•170 variables were identified including independent, dependent, and intervening in Vensim.•Elements impacting 13 topical NBS issues were obtained via Causality Diagrams (CDs).•There were 276 causalities, and an aggregated CD was mapped for the topical issues.•Six enablers and seven barriers of NBSs in Iceland were detected.