The Croatian Beech Forests belong to the Illyrian Beech Forest Region. The refuge areas in this region were of the utmost importance for the European postglacial expansion process of the beech.
Within this area, the beech survived the last ice age and began its expansion to Central and Eastern Europe 12,000 years ago. The majority of European beech in Central Europe belongs to the same genetic group that is typical for the Illyrian region.
Most of the impacts on the forest occurred in the period between the 17th century and 1945. Today, the beech is the most widespread species of forest tree in Croatia, covering 47% of the Croatian forest area.
The World Heritage properties in Croatia comprise the strictly protected Hajdučki and Rožanski Kukovi Nature Reserve in the Velebit National Park and two component parts within Paklenica National Park in the southern section of the Velebit Mountains. The Hajdučki and Rožanski Kukovi Strict Reserve harbours very old beech, but nonetheless are the trees of the upper tree line not massive here. The extreme weather and rough terrain formed the trees into a kind of natural bonsai, which grow very slowly and can at time be twisted and dwarfed.
At Paklenica National Park, the forests are unique habitats under the influence of three climatic types: Mediterranean, continental, and alpine. The old beech forests there represent the largest and oldest dominant beech forest complex on the Eastern Adriatic Coast.