Increasingly, exotic animals and plants are being intentionally and unintentionally introduced into Europe from areas where they naturally occur. In Germany alone, more than one thousand invasive alien species (IAS) are registered. Invasive species cause significant changes to species communities and ecological systems and are considered one of the most important risks to biological diversity. Because they transmit diseases or serve as intermediate hosts for pathogens, they threaten the health of humans as well as pets, livestock and wildlife. The EU Commission estimates the annual economic and health damage caused by IAS in Europe at 9.6 to 12.7 million euros. In the course of globalization and the increasing population and settlement density, invasive species are also attaining increasing significance in cities.