Reducing vulnerability to natural hazards is a shared responsibility of risk management authorities and populations, who are expected to implement safety precautions (e.g., securing furniture to wall studs in houses) and refrain from harmful behaviours (e.g., avoid parking in alluvial areas during flood alerts). In this paper we analyse resilience as a public good, where the individual interest (saving time and money, instead of investing in preventive measures) is often in conflict with that of the whole community (being prepared for potential crises). We hypothesize that, as in other real-life social dilemmas, trust among group members can encourage individual contributions to public safety, by counteracting the fear of other members' defection. However, we also argue that the beneficial effects of trust on collective risk preparedness are conditional upon some key factors, namely, group stability and reputational pressures. We conducted three empirical studies to investigate subjects' decision-making dynamics about collective prevention in the face of risk from natural hazards. Our results suggest that trust in one's peers does increase willingness to contribute to collective risk preparedness (Study 1), and that this effect is based on expectations of direct reciprocity, thus requiring group stability to emerge (Study 2); moreover, the beneficial effect of trust is predicated on the presence of an external observer, whereas in the absence of reputational pressures willingness to invest in risk prevention decreases with trusted peers, thus indicating exploitation motives (Study 3). Taken together, these findings highlight a number of potential implications for participative risk prevention policies.
