Beavers are diverse forest landscapers

Beavers are diverse forest landscapers
In addition to beaver-induced flood sites, the landscape can feature post-flood beaver patches that are fertile ground for deadwood, which can be used by various organisms, such as insects, fungi and lichen. Credit: Pasi Korpelainen and Timo Kumpula, IBC-Carbon project, University of Eastern Finland

Beavers are ecosystem engineers that cut down trees to build dams, eventually causing floods. Beaver-induced floods make forest landscapes and habitats increasingly diverse, but very little is known about the long-term effects of beavers on European landscapes. Researchers at the University of Eastern Finland and the University of Helsinki examined the history and occurrence of beaver-induced floods and patch dynamics in southern Finland. They used a unique dataset of field observations from 1970 to 2018.

Floods caused by over the course of history form a network of different habitats that remain interconnected even for long periods of time.

"Beavers can help to restore wetland ecosystems and entire boreal forests, and they also help in conserving the biodiversity of these environments," researcher Sonja Kivinen from the University of Eastern Finland says.

The European beaver was hunted to extinction in the 19th century Finland. Nowadays, the study area is home to the American beaver, which was introduced there in the 1950s. The American beaver builds similar dams as the European one.

"The spread of the beaver in our study area has created a diverse and constantly changing mosaic of beaver ponds and beaver meadows of different ages," Kivinen says.

In 49 years, number of beaver-induced flood sites grew 11-fold

The researchers observed that the number of beaver-induced flood sites grew by more than 11-fold over the study period. In addition to creating new flood sites, beavers also often use old sites to cause new floods. The duration of an individual flood and the frequency of floods can vary greatly between different sites, resulting in an abundance of habitat patches with different environmental conditions.

Beavers are diverse forest landscapers
Diving beetles, frogs and waterbirds thrive in beaver-induced flood sites. Credit: Sonja Kivinen

"Thanks to beaver activity, there is a unique richness of wetlands in the forest landscape: flowages dominated by bushes, beaver meadows, and deadwood that can be used by various other species," university lecturer Petri Nummi from the University of Helsinki says.

Indeed, beaver-induced disturbances are more predictable in diversifying the forest landscape than for example fires or storms.

More information: Sonja Kivinen et al. Beaver-induced spatiotemporal patch dynamics affect landscape-level environmental heterogeneity, Environmental Research Letters (2020). DOI: 10.1088/1748-9326/ab9924

Journal information: Environmental Research Letters

Citation: Beavers are diverse forest landscapers (2020, June 10) retrieved 26 September 2023 from
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