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Letter to the Editor

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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 …