Climate change impact on Castanopsis sp. pl. endemic to Borneo and its conservation implications

Climate change has become one of the most significant drivers of biodiversity loss, particularly for endemic plant species with narrow geographic distributions. Castanopsis (Fagaceae) comprises several species endemic to Borneo, a region experiencing rapid deforestation and extensive land-use change. The objective of this study is to understand the current and future potential distribution of eight endemic Castanopsis species under two climate change scenarios (SSP2—4.5 and SSP5—8.5) in the late century (2061–2080). Species Distribution Models (SDMs) were developed using presence records of each endemic species and 19 environmental variables, including climate, land cover, soil, and topography. The predictive model shows that most species (six out of eight) are projected to expand their suitable habitats under future climates, particularly in Sabah, Sarawak, and Central Kalimantan. However, two species (Castanopsis densinervia and C. paucispina) show a consistent decline in suitable habitat across all scenarios, highlighting increased extinction risk. Environmental factors, including land cover and climatic variables, differentially influenced the future distribution shifts of the endemic Castanopsis. Conservation actions are urgently required, particularly for species projected to lose habitat, through habitat protection, restoration, and assisted range expansion within climatically stable refugia. This study provides a scientific basis for prioritizing conservation strategies to protect the future of Bornean Castanopsis under ongoing climate change.