Assessing the potential impacts of climate change and their conservation implications in Japan: A case study of conifers

The Japanese archipelago is a biodiversity hotspot with a unique regional climate influenced by the Asian monsoon circulation, surrounding seas, and complex topography. Japan has numerous mountains and islands, which are potentially vulnerable to climate change. This study evaluated the potential impact of climate change on species diversity in Japan, using 25 conifer tree species as a case study. We applied ensemble models based on generalised additive models, artificial neural networks, generalised boostedmodels, and random forests to species' locality records at 1 km2 resolution. The results indicated a substantial impact, such that 80% of the species may lose over half of their current climatically suitable areas by 2100. The lower altitudinal range limits were projected to shift upwards by 293 m on average, suggesting that alpine/sub-alpine and sub-boreal species may face widespread local extinctions. The impacts on sub-alpine species may be moderated by assisted migration to the northern island where they currently do not occur. However, climatically suitable areas for these species and sub-boreal species that occur on the island overlapped significantly, indicating that assisted migration may entail the risk of introducing biotic competition or interbreeding. Thus, rugged topography and dispersal barriers between islands are likely to amplify the future impacts of climate change in Japan. Limited areas in the central mountain region were identified as potential bioclimatic refugia, which should be conserved as a priority.