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In the Inkwilersee (SO/BE) the beaver digs tunnels on an island and destroys the world cultural heritage. Now a solution seems in sight.
The Inkwilersee, a small lake on the Solothurn/Bern canton border, is home to an archaeologically important site. The larger island has remains of pile dwellings in the water, which have been a UNESCO World Heritage Site since 2011.
Only one resident of the lake does not respect the historical find: the beaver. He has been digging tunnels onto the island in the lake for a few years, endangering the valuable remains of the stilt houses.
Now the cantons of Solothurn and Bern have found a solution to keep beavers in check. A grid around the island, which extends into the water, is intended to keep the rodent from digging. “The grid is laid, fixed and covered over the large island and up to 10 meters into the lake,” write the cantons in a joint statement. The trellis is made of steel but still allows plants to grow.
As soon as it is laid, the beaver can no longer dig tunnels onto the island from the embankment. At the same time, experts are building a replacement building for the animal in the lake: this is where the beaver is supposed to move to. Allowing the beaver to be shot would not be a solution, the animals are protected in Switzerland.
Legend:
Measurement of the beaver passages on the big island by employees of the archaeological service of the canton of Bern and the canton of Solothurn.
Archaeological Service of the Canton of Bern/Daniel Steffen.
“First of all, a replacement building for the beavers will be built on the small island on the Bernese side of the lake this winter,” the cantons announced. The grille will not be installed until winter 2023/2024. Because of the closed season, construction is only allowed from November to February. The Inkwilersee is not only an archaeological site of pile dwellings, but also a nature reserve.
Divers found 14 tunnels
During a dive while the lake was being cleaned up (the Inkwilersee had too little oxygen) it was noticed that beavers were digging into the pile dwelling sites. The divers found 14 tunnel entrances on the edge of the island. The beavers worked their way through the tunnels from the water through several layers of construction timber from the Bronze and New Stone Age.
The damage is bad, but there is still something worth doing.
“The damage is bad, but there is still something worth doing. If we wait another five or ten years, that wouldn’t be good,” says Solothurn canton archaeologist Pierre Harb. There are still many finds that need to be secured. He is convinced that in a few years the construction work on the island will be gone. In Bavaria (D), for example, experience has already been gained with such a procedure.
The situation at Lake Inkwil is special for the animals, says Valerie Arnaldi from the Hunting and Fishing Department in Solothurn. The beavers would have a constant water depth in the lake and would not have to dam any water.
It is the optimal solution to grant both protection interests.
The island in the lake serves as a living and sleeping den for a pair of beaver parents and two to four young. On the island everyone is protected from enemies, an ideal home actually.
Conservation organizations agree
The canton of Solothurn explains that nature and environmental protection associations have examined the new project and rated it positively. Total costs for the beaver fence: CHF 800,000. The federal government also pays a contribution to the project. The two cantons of Solothurn and Bern take over the larger part. “It’s the optimal solution for granting both protection interests,” agrees Valerie Arnaldi from the canton of Solothurn.
After the construction work, regular monitoring is carried out to ensure that the project works and that the Unesco World Heritage Site can be protected from the hard-working rodents.