Habitat connectivity shapes biodiversity outcomes in Indonesia’s community-managed forests

1. Social forestry is increasingly promoted as a means to achieve equitable resource governance while contributing to biodiversity conservation. Yet, empirical evidence on how effectively community-managed forests support biodiversity remains limited, particularly in tropical regions.

2. We assessed mammal communities in two contrasting social forestry contexts in Sumatra, Indonesia: (1) a forest-dominated landscape where management emphasised forest retention, and (2) an agroforestry-mosaic characterised by mixed production systems and forest remnants. Using camera-trap data and hierarchical multi-species occupancy models, we compared species richness, community occupancy and the occurrence of forest specialists and globally threatened species between social forestry areas and adjacent watershed protection forests. We also assessed the influence of five environmental (structural connectivity, biomass, forest cover and terrain ruggedness) and anthropogenic (quantified using remoteness) factors in shaping species' occurrence patterns across these multiple-use landscapes.

3. Overall species richness and community occupancy in community-managed forests were comparable to protection forests in both landscapes. However, community composition diverged depending on the landscape context. In the forest-dominated landscape, occupancy of forest specialists and threatened taxa was maintained, while generalist species showed higher occupancy in social forestry areas. Conversely, in the agroforestry-mosaic, forest specialists and threatened taxa had reduced occupancy within social forestry areas, largely driven by lower forest quality and diminished structural connectivity in some areas.

4. Forest structural connectivity emerged as the strongest environmental driver of mammal occurrence. High connectivity buffered biodiversity losses in the forest-dominated community forests, whereas reduced connectivity in the agroforestry-mosaic landscape amplified declines among species with greater forest dependencies. Remoteness further influenced occurrence patterns, particularly favouring forest specialists in the forest-dominated landscape.

5. Synthesis and applications. Our findings suggest that community-managed forests established within predominantly forested areas can make a meaningful contribution to area-based conservation, including recognition as Other Effective Area-based Conservation Measures (OECMs). In community-managed forests established in more modified production landscapes, targeted restoration and actions that enhance habitat connectivity are likely required to sustain populations of priority species. Ensuring that social forestry policies explicitly incorporate biodiversity incentives and connectivity-led management can help align community development objectives with global conservation goals.