Adat governance for sustainable infrastructure in the Lukmen Ring road corridor Jayawijaya, Indonesia

Abstract Infrastructure development in Indigenous territories often extends beyond technical planning and economic investment, involving customary land rights, cultural identity, ecological stewardship, and locally legitimate governance. While previous studies have acknowledged the importance of Indigenous participation in development, limited attention has been given to the institutional mechanisms through which customary authority contributes to sustainable infrastructure governance. This study examines the role of customary institutions in the Lukmen Ring Road corridor, Jayawijaya, Indonesia, using a convergent mixed-methods design that integrates applied ethnography with Partial Least Squares Structural Equation Modeling (PLS-SEM). Qualitative data were collected through in-depth interviews, participant observation, and document analysis, while quantitative data were obtained from 60 respondents representing customary leaders and government institutions. The findings indicate that customary institutions play an active role in land negotiation, participatory decision-making, conflict mediation, project supervision, and the protection of ecological and cultural values throughout the infrastructure development process. The quantitative analysis confirms that customary institutions, infrastructure development policy, and the balance between development and conservation contribute positively to sustainable infrastructure development, while the ethnographic findings explain the institutional and socio-cultural processes through which these relationships operate in practice. By integrating both forms of evidence, the study demonstrates that sustainable infrastructure in Indigenous contexts depends not only on engineering capacity and governmental authority but also on the institutional legitimacy generated through customary governance. The study contributes to the literature by proposing a governance perspective that links Applied Anthropology, Collaborative Governance, and Institutional Analysis and Development to explain how customary institutions strengthen policy legitimacy, community participation, and long-term infrastructure sustainability. These insights provide policy relevance for infrastructure development in Indigenous regions where customary institutions continue to shape public decision-making and natural resource governance.