Scoring environmental and socioeconomic impacts of alien plants invasive in Europe

The categorization of invasive alien spe- cies based on their impact is an important way of improving the management of biological invasions. The impact of 128 alien species of plants in Europe was evaluated using the Generic Impact Scoring System (GISS) originally developed for mammals. Based on information in the literature their environ- mental and socioeconomic impacts were assessed and assigned to one of six different categories. In each category, the impact was classified on a five-degree scale, which reflects the impact intensity. To identify species with the greatest impacts, we used the maximum score recorded in each category and their sums. Data from the whole invaded range were considered, which resulted in scoring the potential impact of each species, not necessarily currently realized in Europe. Environmental impacts are most often manifested via competition with native species (recorded for 83 % of the species), while socioeco- nomic impacts are associated mostly with human health (78 %). The sums of environmental and socioeconomic impacts were significantly correlated, which indicates that the same suite of species traits is associated with both types of impacts. In terms of plant life forms, annual plants have on average lower environmental impacts than perennial plants, and aquatic species have a higher socioeconomic impact than other life forms. Applying the GISS to plants, the most species-rich taxonomic group of alien organisms in Europe, is an important step towards providing managers and policymakers with a robust tool for identifying and prioritizing alien species with the highest impact.