Beavers are master builders that reshape aquatic landscapes with their dams and lodges. The environments they inhabit experience an increase in the biodiversity of aquatic organisms, for example. Now, for the first time, an Eawag study from the wine-growing region known as “Zürcher Weinland” has shown that this is also true for streams in areas given over largely to agriculture. The rodents could therefore be interesting partners when it comes to enhancing bodies of water.
Eradicated at the start of the 19th century, beavers can now be found once again almost anywhere across the length and breadth of the country. Particularly on the Swiss Plateau and in the last ten years, they have become so widespread that five to six thousand individuals are currently estimated to live in Swiss bodies of water.
True master builders
The rodents are known for making significant changes not only to the morphology but also the hydrology and ecology of natural watercourses, making them more dynamic and biodiverse. Until now, however, it was unclear whether this was also true of urban and agricultural streams – in other words, precisely those streams that the beavers predominantly inhabit today. Researchers from Eawag and the University of Lausanne have now shown that this is indeed the case: beaver ponds not only increased the biodiversity of two streams in agricultural areas, but also altered the food supply available to aquatic animals. However, the extent of the beavers’ influence depended strongly on the topography.