A quantitative classification of the geography of non-native flora in the United States

Authors: BRADLEY, BETHANY - University Of Massachusetts, Amherst; EVANS, ANNETTE - University Of Massachusetts, Amherst; SOFAER, HELEN - Us Geological Survey; VILÀ, MONTSERRAT - University Of Sevilla; BARNETT, DAVID - National Ecological Observatory Network (NEON); BEAURY, EVELYN - New York Botanical Garden; Blumenthal, Dana; CORBIN, JEFFREY - Union College; DUKES, JEFFREY - Carnegie Institute - Stanford; EARLY, REGAN - University Of Exeter; IBÁÑEZ, INÉS - University Of Michigan; PEARSE, IAN - Us Geological Survey; PETRI, LAÍS - University Of Michigan; SORTE, CASCADE - University Of California Irvine

Submitted to: Global Ecology and Biogeography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2025
Publication Date: 4/14/2025
Citation: Bradley, B.A., Evans, A.E., Sofaer, H.R., Vilà, M., Barnett, D.T., Beaury, E.M., Blumenthal, D.M., Corbin, J.D., Dukes, J.S., Early, R., Ibáñez, I., Pearse, I.S., Petri, L., Sorte, C.J. 2025. A quantitative classification of the geography of non-native flora in the United States. Global Ecology and Biogeography. 34(4). Article e70041. https://doi.org/10.1111/geb.70041.
DOI: https://doi.org/10.1111/geb.70041

Interpretive Summary: Non-native plants that become abundant are a top priority for natural resource managers, yet non-native abundance remains poorly described across space and among species. This leads to missed opportunities to consistently regulate and manage invasive species across political and jurisdictional borders. Here, we quantify the distribution and abundance of all recorded non-native plants in the conterminous U.S., compiled from 14 spatial datasets. We identify three dimensions of commonness: geographical breadth, habitat breadth, and local abundance. Out of a total, 2031 non-native plant species, 1306 were recorded at high abundance (>10% cover), and 604 species attained all three dimensions of commonness. Ecoregions in the west coast, southeast, northeast, and upper Midwest had the most records of abundant non-native species. By creating a comprehensive categorization of the geography of non-native flora, we provide for the first time a consistent comparison across species and quantify the geographies at risk of invasion. This information can be used to build more consistent regulatory and management practices against potentially problematic non-native species.

Technical Abstract: Non-native plants with the potential to cause ecological and economic harm are a top priority for natural resource managers. Harm disproportionately arises from the subset of species that become abundant, yet non-native abundance remains poorly described across space and among species. Lack of geographical information about where non-native plants become abundant, and potentially invasive, leads to missed opportunities to consistently regulate and manage invasive species across political and jurisdictional borders and hinders our understanding of the processes underlying invasions. Here, we present an empirical analysis of the distribution and abundance of all recorded non-native plants in the conterminous United States (U.S.), compiled from 14 spatial datasets. Drawing from classic macroecological descriptions of species rarity, we used distribution and abundance information to identify three dimensions of commonness: geographical breadth, habitat breadth, and local abundance. In total, 2031 non-native plant species have been recorded in 5,006,910 unique locations. Of these, 1306 non-native species were recorded at high abundance (>10% cover) in 824,750 unique locations. Ecoregions in the west coast, southeast, northeast, and upper Midwest had the most records of abundant non-native species. We identified 1175 species (58% of non-natives) whose abundance and/or distribution indicated that they are common within the conterminous U.S., including 604 species attaining all three dimensions of commonness. Species with higher than expected abundance relative to their distribution (e.g., Lygodium microphyllum, Pennisetum ciliare, Imperata cylindrica) may have high potential to cause ecological harm. By creating a comprehensive categorization of the geography of non-native flora, we provide for the first time a consistent comparison across species and quantify the geographies at risk of invasion. This information can be used to build more consistent regulatory and management practices against potentially problematic non-native species.