Biotic homogenization is primarily driven by native species’ extirpation and the introduction and spread of non-native species, commonly due to human activity 11, 12, 13. The Anthropocene epoch encapsulates the profound effects of human activities on the land surface, oceans, atmosphere, and the evolution of life on Earth, with the implications that these changes have no geological analog 10. Biotic homogenization-declining β-diversity-reduces trait and phylogenetic differences between regions, and is perhaps a more characteristic feature of the Anthropocene than species loss 10.
There has been much focus on species extinctions 6, 7 however, how these biodiversity changes manifest at local to regional scales is still unclear: some studies show declining local diversity 8, while others suggest stable or even increasing species diversity through time 9, and changes in the turnover of species diversity (β-diversity) have been less well studied. Habitat conversion, biotic invasions, anthropogenic climate change, and pollution have contributed initially to dark diversity 1 and eventually to global species losses 2, 3, 4, 5. The timeline of most naturalisations coincides with widespread human migration within the last ~500 years, and demonstrates the profound influence humans exert on regional biotas beyond changes in species richness. Australia, the Pacific and Europe, in contrast, contribute fewer species to the global pool of non-natives, but represent a disproportionate amount of phylogenetic diversity. Asia and North America are major sources of non-native species however, the species they export tend to be phylogenetically close to recipient floras. The extent of homogenization within major biomes is pronounced and is overwhelmingly explained by non-native species naturalizations. Here, using a dataset of >200,000 plant species, we demonstrate widespread and temporal decreases in species and phylogenetic turnover across grain sizes and spatial extents. However, a global assessment of this phenomenon is lacking. Both processes can drive biotic homogenization by reducing trait and phylogenetic differences in species assemblages between regions, thus diminishing the regional distinctiveness of biotas and likely have negative impacts on key ecosystem functions. Native biodiversity decline and non-native species spread are major features of the Anthropocene.