Ecological and socioeconomic correlates of plant invasions in Denmark: the utility of environmental assessment data.

Control of plant invasions requires regional knowledge of invasive species' distribution and the factors that promote their spread. We studied the distribution of invasive alien plants in Denmark at 2 spatial scales ("site" and "municipality") based on habitat descriptions and species lists from 2343 sites recorded within environmental assessments for planned infrastructure projects and conservation management. We created a Geographic Information System database of the sites and supplemented the field data with information on traffic routes, water courses, and socioeconomic indicators from the respective municipalities. The percentage of invaded sites within a municipality decreased with increasing tax percentage and it increased with (sub-)urbanity. The number of invasive species at the sites was positively correlated with resident plant diversity, disturbance, and proximity to traffic routes. We conclude that current plant invasions in Denmark are mainly an anthropogenic (sub-)urban phenomenon. The results are discussed with respect to the utility of environmental assessment data for studying plant invasions and improving control of invasive species.