Examining variation in reasoning about sustainability between diverse populations provides unique insight into how group norms surrounding resource conservation develop. Cultural institutions, such as religious organizations and formal schools, can mobilize communities to solve collective challenges associated with resource depletion. This study examined conservation beliefs in a Western industrialized (Austin, Texas, USA) and a non‐Western, subsistence agricultural community (Tanna, Vanuatu) among children, adolescents, and adults (N = 171; n = 58 7–12‐year‐olds, n = 53 13–17‐year‐olds, and n = 60 18–68‐year‐olds). (...) Participants endorsed or rejected four types of justifications for engaging in land and animal conservation: sustainability, moral, religious, or permissible. In both populations, participants endorsed sustainability justifications most frequently. Religious justifications increased with age in Tanna and decreased with age in Austin. Tannese participants were also more likely to endorse multiple justifications for conservation than Austin participants. Data across all justification types show a main effect of age in both communities; endorsement of conservation decreased with age in Austin, but increased with age in Tanna. Across age groups, participants were more likely to endorse the conservation of animals than land in Austin, yet equally as likely to endorse the conservation of land and animals in Tanna. Overall, these results reveal similarities and differences in the beliefs that support the conservation of natural resources across populations. (shrink)