All around the globe, humans have greatly altered the abiotic and biotic environment with ever-increasing speed. One defining feature of the Anthropocene epoch1,2 is the erosion of biogeographical barriers by human-mediated dispersal of species into new regions, where they can naturalize and cause ecological, economic and social damage3. So far, no comprehensive analysis of the global accumulation and exchange of alien plant species between continents has been performed, primarily because of a lack of data. Here we bridge this knowledge gap by using a unique global database on the occurrences of naturalized alien plant species in 481 mainland and 362 island regions. In total, 13,168 plant species, corresponding to 3.9% of the extant global vascular flora, or approximately the size of the native European flora, have become naturalized somewhere on the globe as a result of human activity. North America has accumulated the largest number of naturalized species, whereas the Pacific Islands show the fastest increase in species numbers with respect to their land area. Continents in the Northern Hemisphere have been the major donors of naturalized alien species to all other continents. Our results quantify for the first time the extent of plant naturalizations worldwide, and illustrate the urgent need for globally integrated efforts to control, manage and understand the spread of alien species.
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We thank the DAISIE team, the CONABIO team, E. Zykova, J. K. Vinogradova, S. R. Majorov, M. Schmidt, M. Newman, P. Thomas, R. Pooma, S. McCune, S. S. Tjitrosoedirdjo, H. Roy, S. Rorke, J. Danihelka, Z. Barina, A. Zeddam, S. Masciadri, Z. Barina and P. Nowak for data contributions, Z. Sixtová, B. Rüter, E. Mamonova, M. Krick, O. Michels and T. Scheu for digitizing data and internet searches, G. Müller and J. Moat for help with shapefiles, L. Cayuela for help with the R package Taxonstand, and T. Blackburn, A. Meyer and M. Rejmánek for comments on previous versions of the manuscript. M.v.K. and W.D. acknowledge funding by the Deutsche Forschungsgemeinschaft (KL 1866/9-1). F.E. acknowledges funding by the Austrian Climate and Energy Fund (project number KR11AC0K00355, SpecAdapt). J.P. and P.P. were supported by the Centre of Excellence PLADIAS (Czech Science Foundation project number 14-36079G) and long-term research development project RVO 67985939 (The Czech Academy of Sciences). P.P. acknowledges support by Praemium Academiae award from The Czech Academy of Sciences. M.W. and M.S. acknowledge funding from the Helmholtz Centre for Environmental Research (UFZ) and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG FZT 118). P.W. and H.K. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) Free Floater Program in the Excellence Initiative at the University of Göttingen and in the scope of the BEFmate project from the Ministry of Science and Culture of Lower Saxony. H.S. acknowledges support by the German VW-Foundation. F.J.C. and M.V. acknowledge support of the project Flora de Guinea Ecuatorial, 4 (CGL2012-32934). N.F. thanks the Projects ICM 05-002, PFB-23 and Fondecyt Postdoc 3120125. J.T. acknowledges the support of the Research Center of the College of Science, King Saud University, Riyadh, Saudi Arabia.
Extended data figures
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