Abstrakt
Using the Global Naturalized Alien Flora (GloNAF) database, this chapter describes the patterns in regional diversity of naturalized alien plants in Europe. GloNAF registered 4139 naturalized plant taxa, which makes Europe the second richest continent after North America, and represents an increase by 390 taxa (or 9.6%) compared to the inventory conducted during the 2000s by the DAISIE (Delivering Alien Invasive Species Inventories for Europe) project.
Most naturalized species are recorded in England (1379), Sweden (874), Scotland (861), Wales (835), France (716), the European part of Russia (649), Ukraine (626) and Norway (595), indicating that the northern part of the continent, in particular the British and Irish Isles and Scandinavia, is most heavily invaded. The rate of new introductions of plants that have become naturalized has increased sharply throughout the two past centuries and is not showing any signs of slowing down.
Biogeographical, socio-economic and ecological factors drive the variation in regional naturalized species richness - high human population density and national wealth, cold temperate and Mediterranean zonobiomes, and habitats such as arable land, coastal habitats and ruderal sites are associated with high numbers of naturalized aliens. Europe has exchanged many species with other continents.
The main donor of naturalized plants to Europe is temperate Asia (1265 more species received than donated); in contrast, Australasia and North America harbour many more naturalized species of European origin than they have supplied to Europe, 1159 and 1080, respectively. The 1926 naturalized aliens from other continents represent a 14.9% contribution to the total plant diversity in Europe.
The most widespread naturalized species is Erigeron canadensis, native to North America, occurring in 47 regions (76%). Fifty-four plants appear on the list of invasive alien species based on impact classification, and four (Acacia dealbata, Lantana camara, Pueraria lobata and Eichhornia crassipes) are among the highest ranking species with potentially the most serious impacts.