Not only people migrate, but over the past few decades also animals and plants have found new habitats. Usually because of trade, new species such as snails and beavers or certain plants were brought to Europe from other countries. In some cases these new species can pose threats to indiginous plants and animals as they sometimes spread uncontrollably and lack any natural enemies which could keep their number in check. Find out more in these presentations which were made by 9th graders in the course of their Biology lessons and which are - unfortunately - in German.