Resurvey of historical moorland plots reveals a landscape-wide increase in the occurrence of woody and non-moorland species over 90 years

Alpine and subalpine moorland communities have been altered by global warming and associated environmental changes. Vegetation changes in moorlands are of concern given the loss of biodiversity, especially among endemic biota, and the potential degradation of important ecosystem services, such as climate regulation and recreation. Although long-term analyses of vegetation data are urgently needed to assess potential vegetation shifts over the past century, when global warming has accelerated, such data are rarely available. In this study, we resurveyed historical moorland plots in 2020, which were surveyed once in 1933, in subalpine ecosystems in northern Japan that have been subjected to little direct human disturbance. We observed a landscape-wide increase in the occurrence of woody species and non-moorland species despite potential resampling errors. Such vegetation changes in moorlands are notable because they have occurred in parallel with the accelerating global warming. Warming can lead to an extended growing season and peat drying, which would explain the changes in vegetation that we observed. We thus provide valuable insights into the very long-term (over 90 years) changes in moorland plant communities. Our study fills a knowledge gap in the inferences of global change effects on mountainous moorlands and adds to the growing evidence that solutions are needed to mitigate the effects of climate change.