LAUSR

Non-technical summary More and more people around the globe experience climate hazards. For vulnerable populations, these hazards not only cause significant physical damages, but can also affect the way people interact with each other. How such interactions are affected by climate hazards is particularly important for understanding the vulnerability of communities. Prosocial behavior is key for communities that heavily rely on informal social support to deal with these threats and for cooperative solutions to provide and maintain public goods. To investigate these effects, we talk to people living on the front lines of climate change and measure their prosociality using behavioral tasks. Our results show that both fast- and slow-onset hazards increase prosociality, underscoring the importance of well-functioning social relationships for dealing with hardship and uncertainty in a variety of contexts. Technical summary People's willingness to engage in prosocial behavior can affect how vulnerable and resilient populations are to climate hazards. We study how different types of climate hazards, fast-onsetting cyclones and slowly rising sea-levels, might affect peoples' prosociality using incentivized behavioral tasks. We sample people who are at the forefront of climate change and either experienced Typhoon Haiyan in the Philippines (study 1; n = 378) or are from sea-level rise hotspots (study 2; n = 1047) in Solomon Islands, Bangladesh, and Vietnam. We experimentally manipulate the salience of these hazards through recall or informational videos. Results from study 1 show that increases in prosociality are (i) independent of whether supportive behaviors or conflicts are recalled, (ii) are not only targeted to a narrow in-group, and (iii) do not come with increases in antisocial behaviors. In study 2, we also find that people behave more prosocial when they are informed about the impacts of rising sea-levels. Our survey evidence suggests that people who already perceive the threat of displacement due to rising sea-levels are also more prosocial. Overall, peoples' responses to both types of hazards are geared toward collective action, which could strengthen their adaptive capacity to deal with climate risks. Social media summary People severely affected by sea-level rise and rapidly emerging climate hazards are responding with increases in prosocial behaviors to fellow villagers.