Conserving omnidirectional landscape connectivity under projected land-use change in Borneo

Land-use change in tropical regions is rapidly diminishing landscape connectivity and threatening the persistence of forest-dependent wildlife. Identifying priority areas for retaining connectivity amid deforestation and infrastructure expansion is particularly urgent in Indonesian Borneo (Kalimantan), where extensive land-use transformation is projected. We evaluated changes in connectivity for three terrestrial taxa with contrasting habitat preferences and dispersal abilities: lesser and greater mousedeer, Tragulus, spp.; Bornean sun bear Helarctus malayanus euryspilus; bearded pig Sus barbatus. Using camera-trap data from 11 study areas, we applied Bayesian occupancy models to estimate responses to anthropogenic and environmental drivers. Occurrence probability maps were converted into resistance layers and integrated into omnidirectional circuit-theory models to map recent (2021) and predict future (2055) connectivity. We quantified changes in Highly Connected Habitat (HCH; >70th percentile current flow) to identify vulnerable areas and species. Production forests are crucial for connectivity, providing up to 62.1% of HCH. However, these areas face the highest projected losses (up to 15% by 2055). While protected areas remain vital refuges, up to one-third of HCH loss is expected to occur in lowland forest, increasing the isolation of existing reserves. Connectivity near Indonesia's new capital site in East Kalimantan is at high risk of degradation, particularly for wider-ranging species. Further, the Trans-Kalimantan Highway's northern link threatens to bisect the relatively undisturbed interior. Our findings highlight the urgent need to preserve and restore connectivity between lowland forest including protected areas, sustainably manage production forests, and proactively integrate connectivity science into infrastructure planning to prevent irreversible forest fragmentation.