Screening new plant introductions for potential invasiveness: a test of impacts for the United States

The economic, health, and environmental costs of invasive plant species suggest the need for screening systems to reduce the probability of importing new harmful invaders. We assessed 105 plant species introduced to the United States since 1995 using the Australian Weed Risk Assessment system and a secondary screen to evaluate the proportion of species that would have been prohibited from import were such a screening system implemented. These tools are likely to result in correct decisions to accept or reject species of unknown invasive potential over 80% of the time. The species tested spanned temperate and tropical locations of origin and represented all vascular plant life forms with the exception of aquatic plants. We had insufficient data to complete assessment of 4% of the species. None of the remaining 101 species were predicted to become invasive: 88% were predicted to be noninvasive and 12% required further evaluation. On average, we required 8 hours to assess each species. These results, in combination with the savings incurred when likely invaders are identified and prohibited prior to import, suggest that this screening system could be implemented to protect the economy and environment and would be unlikely to significantly preclude opportunities for the horticultural industry.