Prospective ecological contributions of potential marine OECMs and MPAs to enhance marine conservation in Indonesia

Other effective area-based conservation measures (OECMs) represent a new frontier in conservation, aiming to acknowledge efforts that contribute to biodiversity beyond marine protected areas (MPAs). Many nations, including Indonesia, are establishing country-specific criteria to define what qualifies as an OECM. However, demonstrating the biodiversity contributions of Indonesia's 382 identified potential OECMs (i.e., non-MPA areas, governed and managed, and likely contributing to biodiversity conservation) poses a challenge due to the absence of national monitoring systems outside MPAs. A spatial approach was used to provide an overview of the expected ecological contributions of potential OECMs upon formal recognition. Potential OECMs were, on average, five times smaller (26,838 ha) than MPAs (133,524 ha). Together with MPAs, they formed a denser conservation network, with many encompassing climate refugia reefs. Upon full recognition, potential OECMs could contribute to conserving <1%, 12%, and 8% of the nation's mangroves, seagrass, and coral reef areas, respectively. Potential OECMs were restricted to coastal areas, and situated in various ecological contexts, including areas typically excluded from MPA designation, such as turbid reefs. Recognizing these OECMs could potentially add 10 million ha to national marine conservation areas. Collectively, MPAs and potential OECMs could contribute to conserving 13% of the nation's waters by 2030. Potential OECMs are effective locally and offer unique strengths, including diverse governance approaches, long-term presence, and potential socioeconomic benefits. Nonetheless, they face challenges from human pressures that may compromise their effectiveness. Formal recognition and strengthening of these areas could help mitigate these risks. This study highlights the potential of recognizing OECMs to enhance conservation efforts in Indonesia, complementing the existing MPA network.