Vegetation and Landscape Shift After Beaver Settlement in a Mountainous Area

Beavers are classified as ecosystem engineers because their activities can significantly alter environmental conditions. Vegetation and landscape changes, based on a series of vegetation maps and satellite images between 1994 and 2022, were studied in a mountain valley of a protected area in the Polish part of the Eastern Carpathians. Eighteen plant communities were identified before the beavers were released, with moist and wet communities covering 76.8% of the area. After 25 years of beaver presence, the vegetation changed: fresh communities decreased from 23% to 10%, and communities with grey alder disappeared. At the same time, the moist and wet communities expanded and new ones developed. Overall, the share of these communities increased to 89% of the area, with the dominant tall herb Filipendulo-Geranietum and <i>Menyanthes trifoliata</i> community. A distinctive feature was an increase in vegetation patchiness with a corresponding decrease in the evenness index. Landscape analysis revealed a 9.5% increase in the length of the streambed and fluctuations in the number of beaver ponds (11-25) and migration corridors (4-20). The number of corridors increased as the availability of grey alder decreased. The total area of the ponds exceeded 2200 m², indicating their significant role in water retention and modifying microclimatic conditions.