Climate-driven niche dynamics of endangered Castanopsis argentea and C. tungurrut in Indonesia

Abstract Predicting suitable habitats and refugia is crucial for species conservation in the face of climate change. This study employed ecological niche modeling (ENM) using maximum entropy principle to assess the impact of projected climate change on two endangered Castanopsis species ( C. argentea and C. tungurrut ) in Indonesia. The objectives were to identify the key climatic drivers, project suitable habitat across the past (Last Glacial Maximum [LGM] and Mid-Holocene [MH]), present, and future (2041–2070 under SSP126 and SSP585), and identify potential refugia of both species. Occurrence data were sourced from GBIF, herbarium records, published articles, and field surveys. Using ten climate variables from CHELSA for initial model construction, we refined models by selecting four key variables for each species. Precipitation in the driest periods emerged as the most significant factor influencing species distributions, highlighting their sensitivity to drought. Historical reconstructions revealed broader suitable ranges during the LGM and MH, except for C. tungurrut in the MH. Future projections indicated habitat contraction under all scenarios. However, potential stable habitats and refugia, particularly in the Sumatran highlands (Bukit Barisan Mountains), Java’s mountain ranges, and scattered parts of Kalimantan, persist despite localized habitat fragmentation. Identification of highly suitable but unrecorded areas, particularly in Aceh, eastern Java, and central Kalimantan, underscores the need for further field surveys to locate potential populations. To manage potential refugia, this study recommends improving management effectiveness inside conservation areas while enhancing community-based forest conservation and promoting sustainable land-use practices outside conservation areas, as well as replanting programs.