Behaviour, political inaction and the adaptation implementation gap: unlocking flood and drought preparedness in public finance through a beta application of the Multi-Actor Behaviour Journey methodology

National adaptation commitments are consistently only minimally translated into funded action, resulting in an enduring adaptation implementation gap. This challenge has appeared relatively intractable, as existing adaptation literature has struggled to specify how recurring political economy barriers to policy implementation can be overcome in practice. We present the first empirical demonstration of a new MultiActor BEhaviour Journey (MABEJ) methodology, developed and iteratively refined through this case study in its initial (beta) form. MABEJ is designed to trace cumulative system outcomes from interdependent behaviours across sequential policy steps, to identify how policy objectives get prioritised or displaced and where practical leverage points for change exist. MABEJ draws on behavioural science, human-centred design, systems thinking and interdisciplinary critical social science perspectives to extend behavioural research to more complex, multi-actor challenges, while accounting for the power dynamics and structural inequalities at the heart of adaptation policy outcomes. This formative application of MABEJ, which continues to undergo further methodological development, examines an acute manifestation of the adaptation implementation gap: the chronic under-prioritisation of flood and drought preparedness in national budgeting processes. We ground this demonstration in Tanzania’s national budgeting process, which resembles public financial management processes elsewhere and exemplifies difficulties translating high-level adaptation commitments into funded action globally. MABEJ diagnoses why gaps between desired and current adaptation outcomes persist, showing where change would matter most, what behavioural determinants would need to shift and who has the capacity to act. This illustrates MABEJ's potential to transform ostensible political and institutional inertia around adaptation into a diagnosable and addressable set of behavioural dynamics, pointing to its value as part of a toolkit for closing the adaptation implementation gap.