Drained by humans, rewetted by beavers—opposing forces shape boreal wetlands

Human activity and natural processes shape boreal forests and peatlands, with opposing forces influencing their transformation. In a recent study conducted in southern Finland, researchers examined the impact of forestry drainage and beaver-induced flooding on the Evo area over the past 60 years. The study, published in the journal Wetlands Ecology and Management, found that the size of the ditch network nearly quadrupled between 1963 and 2023, and the proportion of drained peatlands increased from 23.8% to 72.5%. This expansion reflects a long-term shift toward drier conditions.

For the first time, the study also assessed the total extent of areas flooded by beavers, which now encompasses 77 active and previously flooded sites covering approximately 1.4 square kilometers (0.54 square miles). While drainage is a more extensive hydrological change at the landscape level, beavers create new wetlands and re-establish wetter conditions, particularly along the edges of water bodies.

Sonja Kivinen, a University Lecturer from the University of Eastern Finland, explains that historical analysis helps understand the scale of long-term changes in the wetland landscape, providing a basis for predicting future environmental developments.

Beavers have historically been part of Finland's boreal forest landscapes and have returned to the Evo area, where their impact has intensified. Senior University Lecturer Petri Nummi from the University of Helsinki states that beavers can contribute to wetland restoration by re-establishing natural hydrological processes in drained landscapes without costly restoration measures.

Beaver ponds in headwater areas act like sponges, retaining water and gradually releasing it downstream, which could help mitigate the effects of extreme weather events such as heavy rainfall and droughts in a changing climate.