Current status of invasive alien plants in Ramsar wetlands on Jeju Island, Republic of Korea

Ramsar wetlands are known for their high ecological and economic value; however, in some cases, the indigenous species community is rapidly changing owing to the presence of invasive alien plants (IAPs). To address this issue, we conducted a plant survey of five Ramsar wetland sites on Jeju Island from August 2021 to August 2022 and constructed a list of IAP species. A total of 24 IAP plant species belonging to 13 families were identified. Species of the Asteraceae and Poaceae families, which have high seed production, high adaptability to damaged ecosystems, and a wide range of organisms, from annuals to perennials, were found to be abundant. The distribution of IAP species was consistent with the pattern expected during the early stages of IAP invasion in Korea. Additionally, a positive correlation was observed between the distance from residential areas and the number of IAP species. Wetlands not visited by people were found to be relatively intact, while those frequented by tourists and visitors were susceptible to IAPs. These results suggest that the introduction of IAP species into the Jeju Ramsar wetlands may have been the result of anthropogenic activities, such as tourism. Our study demonstrated that the introduction of IAPs into the Jeju Ramsar wetlands is in its early stages and is mainly attributable to human activity. Therefore, it is necessary to identify the invasion pathways, develop strategies to control or reduce invasion, and control the geographic expansion of these species. Our study highlights the threat of alien species to Jeju Ramsar wetlands, providing the basis for a strategy to protect these wetlands from the threat of invasive species.