thus organised a symposium aimed at civil engineers, to raise awareness of these issues. Beavers are hard to spot but, sometimes, living in such close proximity to humans makes them less shy. This has been observed in Carouge (Geneva), near Beaver Island, a protected area on the River Arve, where some fine specimens can be spotted from a bridge. Beavers look like big marmots with a broad tail, which the animals slap against the water to warn of danger. In Carouge, you can also see how fluidly they swim underwater. www.revue.link/biber contrary – they made a prime habitat for salmon,” he notes. Nature’s allies Once hunted, massacred and scorned, beavers are back. Their population in Switzerland and Liechtenstein has gone from a handful of individuals, when they were first reintroduced, to almost 4,900 animals today, spread across 1,402 territories, according to the Swiss Federal Office for the Environment (FOEN). Their presence acts against the collapse of biodiversity in Switzerland, which itself is linked to the disappearance of wetlands. Over 80 percent of all animal species in Switzerland live in flood plains, according to FOEN. In this situation, there is a natural ally – and an economic one, given that the Confederation has allocated an annual budget of 40 million Swiss francs to support projects to revive and renature rivers – the beaver. On the banks of the Sense, Cécile Auberson points out the trees submerged in the pond. “There are more ecological niches here – in the sun and in the shade – than anywhere else,” she says. Moreover, the wetlands created by beavers act as carbon and methane sinks, trapping these molecules in the water. They also filter out the nitrates produced by farms, among other sources. In addition, these reservoirs contribute to refilling the water table and can buffer the effects of heavy flooding. This is exactly what is needed in an urbanised country like Switzerland, which is threatened by droughts in summer. As a study by info fauna has shown, the dams built by beavers increase biodiversity and biological mass. On average, their presence results in 2.6 times more species and 5.9 times more animals of those species. “The reservoirs I study on the left bank in Geneva have seen the return of kingfishers,” Marie Bessat is delighted to note. The hitch is that beavers are unpredictable in where they create their reservoirs. For example, beavers built dams in an industrial district in Geneva, on the left bank of Lake Geneva, which triggered flooding. The cantonal authorities have responded by monitoring water levels; if they rise suddenly, the height of the dam is lowered to prevent a sudden inrush of water, explains Bessat. In the view of Cécile Auberson, beavers unveil situations where urbanisation failed to take account of the natural environment. “When a road floods, you often see that the rules governing construction, which stipulate a minimum distance between the river and the road, were not followed,” she says. The national beaver centre Biologist Cécile Auberson Photo: Stéphane Herzog Reservoir created by beavers near the Sense, in Zumholz (Fribourg). Photo: Stéphane Herzog “Kingfishers have returned.” Marie Bessat, head of the rural nature programme at the Geneva Cantonal Agriculture and Nature Bureau Swiss Review / October 2026 / No. 4 25
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