Identifying and ascribing the relative significance of introduction pathways for non-native plants into Iceland

The study is aimed at identifying pathways frequently used by non-native plant species, assessing their relative significance and development in time. Pathways were defined following NOBANIS framework (Madsen et al., 2014). Species assessments were based on HARMONIA scheme (Branquart, 2007). Four categories of environmental hazards were assessed plus two additional categories summarizing impacts on health and economy. Temporal development of pathways was assessed using cumulative per annum taxa records. To quantify the activity of investigated pathways over time an index (δ10) showing the number of new species introduced during the period of 10 years was calculated. The study shows that horticulture, landscaping and agriculture can be pointed out as pathways of concern in Iceland. A set of species of concern is also proposed. Two plant taxa are included in A list (high risk species): Anthriscus sylvestis and Lupinus nootkatensis. Three taxa are placed in B list (watch list): Heracleum mantegazzianum, Heracleum persicum and Pinus contorta. Results of the present study are compared with similar studies carried out in Denmark, Scandinavia and Baltic countries. Different measures to prevent introductions of new and potentially dangerous non-native species are also discussed including selection of good practices that may significantly reduce the threat from non-native species used in agriculture and horticulture.