Sustaining biodiversity in coconut-dominated agroecosystems: insights from passive acoustic monitoring

Coconut cultivation is concentrated in coastal and island regions that harbor high species diversity and are particularly vulnerable to disturbance. Yet, coconut sustainability standards lack clear biodiversity safeguards despite rising global demand. We assessed how different coconut production systems influence biodiversity in North Sulawesi, Indonesia, using an acoustic index as a validated proxy for acoustic diversity. Across 56 sites and 2410 recording hours, we compared forests, coconut monocultures, and coconut agroforestry systems, and evaluated the influence of local vegetation and landscape variables on temporal acoustic dynamics. Forests supported the highest acoustic index values, while monocultures were lowest, with pronounced divergence at dawn and dusk. Coconut agroforests buffered these extremes: acoustic diversity remained relatively stable across the day and occasionally approached or exceeded forest levels, suggesting that mixed farming systems can sustain more vocally diverse animal communities than monocultures. Within farms, the density of small trees (primarily cocoa intercrops) was positively associated with acoustic diversity during afternoon period, whereas larger orchard trees exerted weaker influence. At the landscape scale, the proportion of forest cover around a locality was the strongest predictor of acoustic diversity, highlighting the role of forest vegetation in maintaining biodiversity across production landscapes. Our findings confirm that natural forests are irreplaceable for biodiversity, but coconut agroforestry can provide meaningful ecological benefits when embedded in forested landscapes. These insights underscore the need for emerging sustainability frameworks to incorporate explicit biodiversity criteria, including forest retention, intercrop diversity, and vertical structure, and to align with cross-commodity standards such as those in cocoa, given that coconut and cocoa are frequently intercropped.