Quantifying vulnerability to plant invasion across global ecosystems

The widely-referenced "tens rule" in invasion ecology suggests that 10% of established, non-native species will become invasive. However, the accuracy of this estimate has been questioned, as the original analysis focused on small groups of plant species in Great Britain and Australia. Using a novel database of 9,501 established and 2,924 invasive plants, we provide a comprehensive evaluation of plant invasion rates and the first empirical analysis of how the tens rule varies across climate zones and spatial scales. We found that invasion rates ranged from 17% at the country scale to 25% at the continental scale. Tropical communities are often considered to be resistant to invasion, however our results showed significantly higher invasion rates in the tropics and especially on tropical islands, suggesting unexpectedly high vulnerability of these species-rich ecosystems. Our analysis provides improved, environment-specific estimates of invasion rates which are often twice as high as previous expectations. We recommend that practitioners reject the tens rule for plants and adjust future management practices to reflect these updated estimates of invasion risk.