A review of the impacts of major terrestrial invasive alien plants in Ireland.
Invasive alien plants represent a major threat to Ireland's biodiversity and ecosystems, not only in productive or disturbed areas but also in habitats of high conservation value. With a focus on the major terrestrial invasive alien plants occurring in Ireland, we performed a systematic review of current knowledge on a wide range of environmental impacts of plant invasions. These include modifications to native or resident plant communities, alterations in the functioning of native ecosystems and associated ecosystem services, including supporting, regulating, provisioning and cultural services, as well as any positive effects. Overall, we found that rigorous quantitative assessments of the ecological impacts of these species, including comparative studies, are available for few species only and mainly focus on changes in the standing vegetation, while there is a paucity of data on how or if they contribute to alterations in the services provided by native ecosystems, even in protected areas. We conclude by highlighting the need for information on the long-term impacts of plant invasions in Ireland, including potential local, regional, or national extinctions, and the regeneration potential of native plant communities in invaded areas, which ultimately depend on the reversibility of these impacts.