Conservation scientists and practitioners
have long recognized that not all non-native
species pose a threat to biodiversity, yet some ecologists still fail to grasp this message (1). The conclusions drawn by Thomas and Palmer (2) that non-native plant species are not a threat to floral diversity in Britain highlight how this lack of understanding can lead to inappropriate analyses and misleading inferences regarding the impacts of non-native species. Thomas and Palmer base their conclusions on an analysis of the Countryside Survey (CS): this valuable dataset depicts large-scale vegetation changes in common habitats, but its stratified random design does not provide a comprehensive assessment of the impacts of non-native plant species on native biodiversity
