Biological invasions threaten global biodiversity and is also considered a major cause of recent extinctions. Human activity contributes to invasions through different mechanisms, but the rapid speed and patterns of invasion are large unexplored.
In China, 268 invasive plants species have been described, and in this study, researchers trace the origin and spread rate of 17 the worst invaders using a collection of data from herbaria, monitoring programmes, literature and own field surveys. They use GBIF-mediated data of non-invasive species to normalize their dataset, and find the average minimal speed across all species to be 1.5 km per year, with some species spreading more than 100 km per year.
These rates are unlikely to be explained by spread of seeds by the animals, water or wind, and in fact, the study finds a significant correlation between number of private-owned cars in China and counties with invasive species, providing further evidence for human-mediated spread.