Beavers in Switzerland built dams in 16 streams that were disturbed by humans. Their hard work slowed down water and helped restore aquatic wildlife

Beavers are often called nature's engineers and there is a very good reason for this. These creatures build dams from branches, mud and other natural materials, altering the flow of water through a landscape. In Switzerland their work of building dams has helped to restore streams so that more aquatic wildlife can flourish, even in highly farmed and urbanised areas.

A study published in the Journal of Applied Ecology on June 8, 2026, has revealed how beavers have affected 16 streams in Switzerland. The results implied that beavers could enhance biodiversity even in areas with high human influence on the surrounding landscape, but the benefits might differ between species and sites.

New homes for aquatic wildlife

Researchers compared sites with beaver-built dams with sites without beaver activity. They observed a wide variety of aquatic and terrestrial animals, including amphibians, fish, dragonflies, plants, plankton, bats and invertebrates.


Results showed that beaver activity was generally beneficial to amphibians, dragonflies, aquatic plants and plankton, with higher species number and abundance at dammed sites. Species richness of fish and terrestrial plants also increased, but not the same way in terms of overall abundance.

The results suggest that beaver dams are not equally beneficial to all groups of organisms but their overall effect, however, was positive for biodiversity across the landscapes examined.

Why dams are important to streams

Beavers alter the shape of waterways by slowing the flow of water, trapping sediment and nutrients and inundating parts of the surrounding land. These changes can turn stretches of fast-moving streams into ponds and wetland habitats for species that need slower water.

An earlier study by researchers from Eawag, the Swiss Federal Institute of Aquatic Science and Technology, and the University of Lausanne found similar benefits in two agricultural streams in the Zürcher Weinland region.

The dams trapped sediment and nutrients that would have flowed downstream otherwise. The new habitats are home to a variety of species, including endangered dragonfly larvae.

But how much these changes occurred depended on the shape of the land around the stream beacuse a stream that is shallow has more room to spread and hence can form wider ponds than the one with steep banks.

In the 2026 study, some species showed a decrease in benefits with increased intensity of human land use.

Even then, the study has found that beaver activity over all improved local biodiversity across a range of settings, from more natural areas to human-altered environments.