Effects of Forestry Transformation on the Ecosystem Level of Biodiversity in Poland’s Forests

This paper presents the results of an analysis of the effects of Poland’s forest management evolution over the last 75 years on forest biodiversity at the ecosystem level. Forest biodiversity changes in the two politically and economically different eras (socialism and democracy) are interpreted based on four indicators used in assessments of forest stands (naturalness; habitat diversity; forest management system; forest stand age structure). In the era of socialism (1945–1989), there were dynamic increases in the area of semi-natural forests as well as in the proportion of the most fertile habitats, whilst the proportion of the poorest habitats decreased quite dynamically. Then, the clearcutting management system was regularly implemented, with adverse impacts on forest spatial structure diversity. The proportion of old/mature tree stands and the stand average age increased at relatively slow rates. In the era of democracy (1990–2020), there were comparatively more dynamic increases observed in the area of forests undisturbed by man, as well as in the proportions of mixed broadleaved and wetland forest habitats. At the same time, the proportion of old/mature stands and stand average age kept increasing at relatively fast rates. The area of forests managed with the use of the shelterwood system increased and the area of forest plantations substantially decreased. On the other hand, irrespective of the era under study, there occurred a noticeable not-so-favourable decreasing trend in the proportion of the youngest forest stands. All in all, during the analysed period of more than seven decades, the evolution of forest management practice implemented in Poland’s forests by State Forests National Forest Holding led to the restoration of/an increase in biodiversity at the ecosystem level. Yet, there have remained unsolved issues, as regards the following aspects: organisational (the assurance of further reconstruction of forest stands, and the restoration of water profiles), political (a lack of up-to-date national forest policy), and financial (the costs of protecting/restoring biodiversity vs. State Forests’ self-financing), as well as conceptual (old-growth stands in managed forests, and controversy over clearcutting) and natural/anthropogenic (climate change, and the eutrophication of forest habitats) issues. The solutions may require measures outside the limits of Poland’s forestry, if not far beyond national borders.