Assessing the Impacts of Changing Landscapes on Terrestrial Mammals across Indonesian Borneo

Tropical forests are regarded as one of the most biologically important ecosystems on Earth but are increasingly threatened by rapid environmental change driven by human activities. Deforestation and overexploitation have led to disproportionately higher biodiversity losses in the tropics compared to other biomes, particularly for terrestrial mammal species. As the human population and demand for natural resources continue to rise, further land transformations are anticipated in tropical countries - including proliferating infrastructure expansion into previously inaccessible areas. To balance economic development alongside biodiversity conservation goals, proactive and coordinated conservation efforts based on strong empirical evidence are urgently needed in these regions.

Kalimantan - the Indonesian portion of Borneo - exemplifies these challenges. The region has experienced rapid deforestation over the past 50 years and remaining forests are set to be altered further by extensive infrastructure development. Broad-scale conservation strategies that consider biodiversity data across multiple regions, years and species are needed, but this approach is hindered by a lack of standardised wildlife monitoring. In my PhD thesis, I collated camera-trap data from field researchers working across Kalimantan and analysed this information using standardised frameworks that account for heterogenous data and imperfect species detection. Throughout, I utilise hierarchical occupancy modelling and additional spatial appraisals, including a landscape connectivity assessment with electrical circuit theory. My research adopts a community-wide perspective, offering insights for multiple terrestrial mammal species, even those that are rare. I also maintain a focus on the Bornean sun bear as a case-study species throughout, due to its vulnerability to both environmental and anthropogenic pressures.

In Chapter 1, I investigate the potential impacts of large-scale infrastructure development (the relocation of Indonesia's capital to East Kalimantan, and associated road development) on critical habitat of threatened mammals. This emphasised the importance of considering secondary disturbances, which can occur further from the infrastructure core, in environmental impact assessments to avoid an underestimation of the repercussions for wildlife. In Chapter 2, I assess the temporal occurrence dynamics of the terrestrial mammal community within three lowland protected areas (PAs) across 6 to 10 years. Collectively, the probability of site-use ("habitat-use") increased for 12% of mammals, whilst 39% remained stable and 49% exhibited declines. However, biodiversity trajectories were highly variable between PAs and dynamics were driven by conditions beyond the park boundaries. Finally, in Chapter 3, I conduct a landscape connectivity assessment in relation to future deforestation and infrastructure development scenarios, focusing on the sun bear as a case-study. This identified regional priorities for mitigating connectivity losses and emphasised the importance of restoring connectivity between the PA network, particularly in the lowlands.

Collectively, this research provides new insights into the spatial and temporal trends of mammal occurrence in Indonesian Borneo, as well as the ways that infrastructure impacts could be mitigated, and PA effectiveness could be improved. I provide recommendations based on this evidence for guiding conservation in relation to the anticipated landscape change which can be incorporated into land-use planning. Finally, my thesis demonstrates the importance and feasibility of data-sharing amongst researchers to provide the information needed to help tackle imminent and large-scale conservation issues in tropical countries.