For centuries, Swiss farmers have sent their cattle, goats and sheep up the mountains to graze in warmer months before bringing them back down at the start of autumn. Devised in the Middle Ages to save precious grass in the valleys for winter stock, the tradition of “summering” has so transformed the countryside into a patchwork of forests and pastures that maintaining its appearance was written into the Swiss Constitution as an essential role of agriculture.

It has also knitted together essential threads of the country’s modern identity — alpine cheeses, hiking trails that crisscross summer pastures, cowbells echoing off the mountainsides.

In December, the United Nations heritage agency UNESCO added the Swiss tradition to its exalted “intangible cultural heritage” list.

But climate change threatens to scramble those traditions. Warming temperatures, glacier loss, less snow and an earlier snow melt are forcing farmers across Switzerland to adapt.

Not all are feeling the changes in the same way in a country where the Alps create many microclimates. Some are enjoying bigger yields on summer pastures, allowing them to extend their alpine seasons. Others are being forced by more frequent and intense droughts to descend with their herds earlier.

The more evident the effect on the Swiss, the more potential trouble it spells for all of Europe.

Switzerland has long been considered Europe’s water tower, the place where deep winter snows would accumulate and gently melt through the warmer months, augmenting the trickling runoff from thick glaciers that helped sustain many of Europe’s rivers and its ways of life for centuries.