Abstract
Based on a spatially explicit data set of more than 27,000 non-native plant presence records for South Africa's Kruger National Park we examined the role of boundaries in preventing colonization of protected areas by non-native species. The number of records of non-native invasive plants declined rapidly beyond 1500 m inside the park; thus the park boundary limited the spread of non-native plants.
The number of non-native invasive plants inside the park was a function of the amount of water runoff, density of major roads, and the presence of natural vegetation outside the park. Of the types of human-induced disturbance, only the density of major roads outside the protected area significantly increased the number of non-native plant records.
Our findings suggest that the probability of incursion of invasive plants into protected areas can be quantified reliably.