Opuntia species and similar cacti have also proliferated in some of the hills around the capital of Valais, in Sion, where estimates suggest Opuntia plants now make up 23-30% of the low vegetation cover. Their presence has also been reported in neighbouring Alpine regions, including Ticino and Grisons in Switzerland, and the Aosta valley and Valtellina in Italy.
In Sion, estimates suggest Opuntia plants make up 23-30% of the low vegetation cover Photograph: pob/Peter Oliver Baumgartner
“In some parts of Valais, we estimate that the cacti can occupy one-third of the available surface,” says Yann Triponez, a biologist who works in the canton of Valais’ nature protection service. He says Opuntia have been present in Valais at least since the late 18th century, when it was imported from North America.