At the end of September, the 11th Symposium “Kopački rit – past, present, future” was held with international participation in Osijek (Republic of Croatia). The Symposium was organized by the State University “Kopački rit Nature Park”, the Faculty of Agrobiotechnical Sciences Osijek, and a number of other institutions of the Osijek-Baranja County. The organization was supported by the international organizations Network of Protected Areas along the Danube River (DANUBEPARKS) and the Balkan Environmental Association (B.EN.A). Thematic focus of the Symposium was biodiversity, ecology and protection of the “Kopački rit” Nature Park, as well as the problems of protecting natural resources and goods along the Danube. About 70 presentations were held at the Symposium, and among them experts from the JP “National Park Đerdap” participated, who presented the work “Invasive species on the example of the pajasen (Ailanthus altissima (Mill.) Swyngler, syn. Ailanthus glandulosa Desf, in the National Park “Djerdap”.