Flora of Geogeumdo Island

We investigated the flora of Geogeumdo Island in the southernmost part of Goheung-gun County, Jeollanam-do Province, and discuss the significance of the plants found. To assess vascular plant diversity on the island, we conducted 30 field surveys over 46 days, from April 2015 to May 2025. As a result, we identified 852 taxa, comprising 131 families, 446 genera, 772 species, 14 subspecies, 60 varieties, and six forms. Among them, 203 are floristic regional indicator plants designated by the Ministry of Environment: six taxa in grade V (e.g., <i>Cymbidium macrorhizon</i> Lindl.), 16 in grade IV (e.g., <i>Impatiens furcillata</i> Hemsl.), 67 in grade III (e.g., <i>Microlepia marginata</i> (Panz.) C. Chr.), 28 in grade II (e.g., <i>Phacellanthus tubiflorus</i> Siebold & Zucc.), and 86 in grade I (e.g., <i>Ainsliaea apiculata</i> Sch. Bip. ex Zoll.). We also found 24 plants endemic to Korea and 11 International Union for Conservation of Nature (IUCN) Red List plants on the island, specifically four endangered (EN), one vulnerable (VU), and six near-threatened (NT) species. Additionally, voucher specimens confirmed six ecosystem-disturbing (destructive invasive) plants and 80 naturalized plants designated by the Korean Ministry of Environment. Furthermore, 139 southern plant species with limited distribution areas on Jeju Island (<i>Carex teinogyna</i> and <i>Isachne nipponensis</i>) and the southern coast (e.g., <i>Thelypteris beddomei, Teucrium viscidum,</i> and <i>Brachyelytrum japonicum</i>) were found on Geogeumdo Island. These findings serve as crucial baseline data, supporting the northward shift of southern plants as a result of climate change.