A recent study have shown that the number of native plant species in Europe is rapidly declining. Many native species such as the Blue Woodruff (Asperula arvensis), are becoming rare, and almost extinct. The Blue Woodruff is a type of weed that used to thrive in Germany and Austria but is now confined to Italy and Spain because of the agricultural practices, loss of habitat, and urbanization in Europe. Ironically, scientists claim that the biodiversity is actually increasing in Europe because of the increased number of alien species. One negative effect of alien species is that it cause plant communities to become more homogenous since the invasive alien plants become evenly distributed across the continent.