Wetland transformations under contrasting disturbances: anthropogenic drainage expansion and beaver‑induced flooding

Abstract Wetland ecosystems, including boreal peatlands, have been widely altered by anthropogenic disturbances, resulting in long‑term changes to ecosystem functioning and biodiversity. Across northern Europe, forestry‑driven drainage has substantially modified peatland water regimes, whereas beavers, as natural ecosystem engineers, represent a contrasting disturbance process by locally re‑establishing wetter conditions. We studied hydrologically driven landscape changes by analyzing anthropogenic drainage in 1963 and 2023 alongside beaver‑induced flooding in the Evo area in southern Finland using historical maps, aerial imagery, and long‑term field observations. Drainage and beaver-induced disturbances were examined both at the landscape scale and within waterbody buffer zones representing transitional areas between aquatic and terrestrial environments. The results showed that the ditch network expanded substantially over the study period, with total ditch length and ditch density increasing approximately fourfold. The proportion of ditched peatland increased from 23.8 to 72.5%. Beaver-induced flooding formed a mosaic of 77 sites, covering a total of 1.4 km 2 (1.1% of the landscape). Beaver-flooded areas overlapped 3.9% of ditched peatlands at the landscape scale and 14.5% within the waterbody buffer zone. Our results demonstrate that long-term forestry-driven drainage has profoundly altered boreal landscapes, highlighting the importance of understanding historical conditions in relation to present-day landscape patterns. From a restoration and management perspective, beaver‑induced flooding supports ecological resilience by introducing local hydrological dynamics at aquatic–terrestrial interfaces and creating wetland mosaics in extensively drained landscapes. Our study suggests the potential for integrating natural ecosystem engineering into wetland restoration strategies.