This paper examines rice biocultural diversity in Sarangani province, southern Philippines through a socio-anthropological lens. Participatory rural appraisal highlighted the cultural importance of upland rice and the entire suite of farming rituals practiced by ethnic communities in the area. Further unveiled by the study were concomitant rice varietal losses, a highly eroded indigenous knowledge system, or IKS, as well as major driving forces that have significantly impacted biocultural diversity on-farm. Sociological analysis of Sarangani tribal community and resources identified upland rice as a potential cultural keystone species (CKS) whose loss can severely compromise cultural integrity and food security. However, halting biocultural erosion while ensuring human wellbeing can become complicated and constrain conservation initiatives. The CKS model, albeit potentially subjective and controversial, can provide valuable insights for the development of sustainable conservation strategies specifically suited to the Sarangani upland situation. Strengthening of awareness among stakeholders about the link between traditional culture, conservation, and food security is necessary if significant results are to be achieved.