Ecological decline and biocultural loss in Cycas revoluta landscapes of the Amami Islands

Cycads (Cycadales) are one of the world’s most ancient plant lineages, and Cycas revoluta Thunb. (‘sotetsu,’ in Japanese) has long occupied a central place in the cultural ecologies of the Ryukyu archipelago, particularly in the Amami Islands of southern Japan. Although never domesticated, C. revoluta has held enduring alimentary, ethnoecological, and symbolic saliency within local agroecological systems, ritual landscapes, and island identities for centuries. Building on recent interdisciplinary scholarship on Japanese and Ryukyuan cycad cultures, this presentation synthesizes ethnobotanical, historical, ecological, and genetic research to detail the accelerating collapse of Amami cycad biocultural heritage. The core of this talk focuses on results from ongoing fieldwork documenting the rapid spread of cycad aulacaspis scale (Aulacaspis yasumatsui Takagi), an invasive insect that now poses an existential threat to both biological C. revoluta populations and sotetsu culture across the Amami archipelago. Drawing on systematic botanical surveys, geospatial mapping, genetic sampling, and ethnographic interviews, the presentation details how ecological decline and cultural erosion are unfolding in tandem. Population-level mortality, reproductive failure, and genetic loss are paralleled by the disappearance of knowledge, practices, and senses of place historically anchored in the islands’ cycad landscapes. By situating these findings within broader discussions of cycad use in Japan and worldwide, as well as comparative biocultural heritage studies, the presentation highlights how invasive species can rapidly destabilize long-standing human-plant relationships. The Amami case underscores the urgency of integrating biological conservation with cultural documentation at moments of irreversible ecological change, offering broader insights into island resilience, heritage loss, and the fragility of biocultural systems under accelerating environmental pressures.