Instead of high value willow-poplar galleries and ash-oak-elm galleries stands of non-indigenous species are present at many sites of the flood plain of Danube in the Beda-Karapancsa Region of the Danube Drava National Park. According to the Act of Nature Conservation in Hungary minders of the territories are obligated to change non-indigenous tree species to natural tree species in all forest stands (e.g. monocultures), that are on protected areas. Change of forest structure has to be determined by the recent type of stand, the future stand and the site; its speed is fitted to the whole territory. The affects of water regulation works on the area must be taken in regard. It is necessary to monitor the results of the changes of forest structure by indicators of naturalness. It can be done by the method of naturalness value of forest stands (TERMERD).