Biological invasions are processes of species spreading outside their native range. By alien species, we mean species that occur freely in an area outside their previous range and establish self-sustaining populations there. The decisive factor here is that the occurrence of the species in the area was previously prevented by dispersal barriers and not by the site conditions of the new area. Biological invasions are often the reason for specific restoration projects, but they can also be unintentionally encouraged by the disturbance associated with restoration.

Biological invasions are not only an ecological and biogeographical issue, but also have an economic and social dimension. It is therefore an interdisciplinary field of work with a bioscientific core. We are primarily concerned with ecological issues relating to the spread of species outside their native range. We are particularly interested in the mechanisms of biological invasions, which we study using both plants and animals. The combination of plant and animal ecology projects enables generalizing conclusions and the development of new control methods, e.g. in the context of renaturation projects.