The knowledge and values of local communities are now being acknowledged as valuable for biodiversity conservation. Relationships of trust, reciprocity and exchange, common rules, norms and sanctions, and connectedness in groups are what make up social capital, which is a necessary resource for shaping individual action to achieve positive biodiversity outcomes. Agricultural and rural conservation programs address biodiversity at three levels: agrobiodiversity on farms, nearby nature in landscapes, and protected areas. Recent initiatives that have sought to build social capital have shown that rural people can improve their understanding of biodiversity and agroecological relationships at the same time as they develop new social rules, norms, and institutions. This process of social learning helps new ideas to spread and can lead to positive biodiversity outcomes over large areas. New ideas spread more rapidly where there is high social capital. There remain many practical and policy difficulties, however, not least regarding the need to invest in social capital formation and the many unresolved questions of how the state views communities empowered to make their own decisions. Nonetheless, attention to the value of social relations, in the form of trust, reciprocal arrangements, locally developed rules, norms and sanctions, and emergent institutions, has clearly been shown to deliver a biodiversity dividend in many contexts. This suggests a need to blend both the biological and social elements of conservation.