Engaging customary law to improve the effectiveness of marine protected areas in Indonesia

Customary law has been acknowledged worldwide for its ability to increase the effectiveness of conservation projects such as Marine Protected Areas (MPAs). In Indonesia, the acknowledgement of customary law is clearly written in a decree formulated by the national government. However, our understanding of how customary law supports, interacts with, and complements conservation remains limited. Here, we explore the role of customary law in helping MPAs achieve their goals in Indonesia. We characterise how customary and formal regulatory conservation management intertwine when local communities manage their natural resources. We studied two MPAs located in the west (Sabang Island) and east (Nusa Penida Island) of Indonesia. There, we gathered both quantitative and qualitative data from a total of 360 respondents using questionnaires, in-depth interviews, and focus group discussions to investigate community knowledge of and perspectives on customary or adat law, the history of adat law and how it is currently applied, and the practise of both adat and formal regulatory conservation management. Our analysis assessed quantitative data using statistical analysis in R, and qualitative data with thematic analysis in NVivo. Most of our respondents were positive about the application of adat law to manage and protect the environment, thus customary law was found to be effective in supporting the goals of MPAs. However, our findings suggest that the full integration of customary law and formal regulatory conservation management can be difficult to achieve, as they rely on different principles for deciding policy and implementing sanctions. If integration is to be achieved, we suggest both systems need to be: (1) flexible; (2) widely communicated; and (3) clearly written.