The Primeval Beech Forests represent examples of on-going post-glacial biological and ecological evolution of terrestrial ecosystems and are indispensable to understanding the spread of the beech (Fagus Sylvatica) in the Northern Hemisphere across a variety of environments.

Thanks to this fact, the primeval forests of Stužica, Rožok and Havešová in the Bukovské vrchy Mountains and Kyjov primeval forest in the Vihorlatské vrchy Mountains in Chránená krajinná oblasť (Protected Landscape Area) Vihorlat are of world importance. The first three of them are situated in the area of the Poloniny National Park.