A habitat is not determined by its size or the ability to self-balance (as in the case of ecosystem). It is a large or a small area which is a »home« to a certain animal or plant.
There are at least 6 forest associations within the park, and the most interesting among them is probably Vicio oroboidi-Abietum above Zagorje and a well-spread association of Haquetio-Fagetum. There are about 30 grassland associations that mostly belong to the following groups: Brometalia erecti, Molinietalia, Arrhenatheretalia, Phragmiti-Magnocaricetea, Filipendulion and Petasition officinalis. These associations cover humid plains as well as dry highland sub-Alpine areas and the areas that are significantly influenced by human activities.
In Kozjanski Park, high-trunk orchards present the most important habitat for endangered bird species. Extensive grasslands are also significant, both dry (slopes of Kozjansko) and humid types (Obsotelje, Jovsi). IBA does not include large forest areas in Kozjansko, since forest is not among the most essential bird habitats.