Ecosystems of Białowieża Primeval Forest are characterized by a high degree of naturalness and biodiversity. Changes in species and age structure in the long-term period resulted from both natural processes and human impact (indirectly and directly).
The assessment of changes and knowledge about the current state allows to decide what protective measures should be taken to improve the condition of forest ecosystems. One can also evaluate the processes taking place and their direction, and therefore also assess the need for any actions.
In the conducted research, the changes occurring in forest ecosystems with particular emphasis on spruce were assessed.

An almost 100-year process of evolution of the species share in stands was analyzed up to 2015 using historical forest management and present spatial information data. Habitat data was used to asses the suitable and unsuitable conditions for spruce dominance. In addition, long-term development model was used for forecasting of the share of this species using data from beginning of 2015. Those results were compared with data from more than 500 sample plots measured in 2016-2018, just after bark beetle (Ips typographus) outbreak in 2015.

Spruce has doubled from 12 to 25% its share of the Bialowieża Forests area in the first half of twentieth century and was stable for the second half. Development model run just before the outbreak suggested stable decrease of spruce share in the horizon of 2065 down to 23%. Habitat model from 2015 was suggesting that spruce suitable sites cover only 12% of the area and only 50% of that area being dominated by spruce; the residue growing in unfavorable habitat conditions. Recent outbreak, with no management control, has dwindled spruce share down below 9%, showing habitual model results being better than development model scenario.