Global exchange and accumulation of non-native plants

A global database of alien plants, showing that over 13,000 species, nearly 4% of the global flora, have become naturalized in a new location. Import and export of plant species Human activity has facilitated the spread of alien plant species around the globe, many of which have become naturalized on different continents. Mark van Kleunen et al . construct a global database of alien plant introductions, showing that more than 13,000 species — nearly 4% of the total flora — have become naturalized in a new location. North America has received the most alien plants, while the Pacific islands are accumulating them at the fastest pace, and the Northern Hemisphere is the predominant donor of alien species. All around the globe, humans have greatly altered the abiotic and biotic environment with ever-increasing speed. One defining feature of the Anthropocene epoch 1 , 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 damage 3 . 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.