The border area in question is beneath the Matterhorn, one of Europe’s tallest mountains, around Italy’s Aosta valley and Switzerland’s Zermatt region, which is home to several popular ski resorts.

In a statement on Friday, the Swiss government said: “Significant sections of the border are defined by the watershed or ridge lines of glaciers, firn or perpetual snow… These formations are changing due to the melting of glaciers.”

A Swiss-Italian commission drafted changes to the border in May 2023. On Friday, Switzerland officially signed the treaty, while Italy has still yet to sign it.

According to a joint report published earlier this year by the UN's World Meteorological Organization and the European Union's climate agency, Copernicus, Europe is the world’s fastest-warming continent.

It warned that glaciers were melting at unprecedented rates due to human-made climate breakdown.

The Swiss Academy of Sciences estimates that Swiss glaciers lost 4% of their volume in 2023, which was the second biggest annual decline on record. The largest decline was 6% in 2022.