Global warming poses major challenges for Swiss viticulture. But the winegrowers could even benefit from the rising temperatures – if they convert their operations in good time. Science provides them with the basics.
The wine-growing region in Leytron in the Lower Valais in November 2019.
July 14, 2022: A light wind is blowing over the vineyards east of Leytron in the Lower Valais, and yet the whole landscape seems to shimmer with heat. The thermometer shows 34 degrees in the shade; however, this is in short supply here. Meanwhile, sweat is beading on his forehead. These temperatures are nothing unusual in themselves, says Vivian Zufferey.
In the Valais summer, the mercury regularly rises above 30 degrees. “But the fact that such values are maintained over a longer period of time is something special.” Like now. Climate change is lengthening the heat waves and changing a lot more. During the drive to Leytron, the typical buzzing of a man cicada could suddenly be heard through the open car window. Zufferey explains that they have become quite common here. “About ten, fifteen years.” In the past, the noisy insects were mainly found in Mediterranean areas.
For Vivian Zufferey, heating has long been a central part of his everyday work. The plant physiologist from the Swiss Federal Research Center Agroscope is investigating the effects of climate change on viticulture – and the possibilities for adaptation. There are many aspects, emphasizes the expert. But first and foremost he reports positive things. In general, Swiss wine will get better, “because we are in the north”.
Higher temperatures make grapes sweeter
More warmth and more sun already ensured better ripening and more sugar in the grapes, especially in the red vines. Aside from that, Zufferey explains, vintners could plant more southern varieties. The new variety stimulates the market. So much for one side of the coin.
However, future problems are hidden in the details. Quite a few of the grape varieties that are popular in this country need cooler weather. Only then will they deliver an optimal product. The Pinot Noir grape variety, for example, is already getting too hot in some Valais locations, reports Vivian Zufferey. Ripening comes too early and the wine is less “fine” after pressing. Certain flavors were missing.
Similar difficulties threaten the Chasselas in the neighboring canton of Vaud. Further north, on Lake Neuchâtel, the local climate of the vineyards has changed from very cool to cool to moderate in recent decades. However, the Pinot noir growing there requires relatively low nighttime temperatures a few weeks before harvest, because this increases the content of certain polyphenols.
The winegrowers could avoid the heat and plant their Pinot Noir at higher altitudes, but this is not (yet) permitted by law.
The right type of wine has to be in the right place
Vivian Zufferey
The expert emphasizes that climate change requires reorientation. “We have to adjust the vineyards.” That means putting the right grape varieties in the right places. And that requires a lot of knowledge. Zufferey and his colleagues collect the necessary data in places including Leytron, where Agroscope operates its own research station.
Here it is systematically tested how viticulture can be better prepared for the future. There are around 200 vine varieties here on around eight hectares of trial areas. The hives are distributed in about 2000 micro-plots, each with different tillage, irrigation and fertilization regimes. Each of these small areas is harvested and pressed separately. The enormous effort is worth it.
The researchers can thus trace the effects of different growth conditions such as the water supply from the still green grape to the ready-to-drink wine. It can hardly be more detailed.
Vivian Zufferey guides the visitor through the plots. The vineyard lies on the sedimentary deposits of a nearby mountain stream, which flows into the Rhone a few hundred meters to the south. So it’s no wonder that the ground consists almost entirely of gravel and gray sand. “Very permeable to water,” emphasizes Zufferey. Only nutrient-poor grassland used to thrive here. In principle, such a subsoil is well suited for viticulture if you manage it properly.
Vegetation around the vines keeps pests at bay
The scientist points to the withered vegetation between two rows of vines. “Spontaneous greening,” he explains. Here nature has been given free rein. The resulting vegetation may not seem like much, but it too can play an important role in the overall fabric of a vineyard.
The Agroscope team is testing different forms of tillage. Some intermediate strips are supplied mechanically, i.e. the surface is plowed up, while others are treated with weed killer. By removing ground cover, the vines get more water and nutrients because there is no competition. However, accompanying greenery made of grass and wild herbs also offers advantages, as Zufferey explains.
“This strip hasn’t been mowed in five years.” That saves work and CO2-emissions; Winegrowers and climate protection benefit. Apart from that, greening counteracts erosion. An additional benefit is the formation of humus. The more or less wild vegetation can also help to keep pests such as spider mites in check because it offers their natural enemies shelter.
In the wine-growing regions of the Agroscope research institute, the grapes are harvested in September and October. They are then made into wine to see which plants produce the best product under which conditions.
In the meantime, Agroscope has developed special seed mixtures for ground cover, the plant species contained in them are characterized above all by their frugality. Bromus tectorum is one of them. The sweet grass, also known by the German name downy brome, is found almost everywhere in Switzerland. However, the variant sown here is a particularly low-growing ecotype, explains Vivian Zufferey. The seeds were collected on dry roadsides in Valais.
The DNA of old grape varieties is valuable
As a result, the little plants are already adapted to the harsh living conditions in the vineyard. By the way, if you take a closer look at the scrubby vegetation, you will quickly see another advantage of greening: the protection of biodiversity. Suddenly the colors of a red-winged grasshopper flare up between the broom stalks. The insect is on the red list of endangered species in this country. Just a few steps away, a praying mantis stalks through the grass.
Agroscope is also committed to promoting and preserving diversity when it comes to wine. The preservation of old grape varieties is important, emphasizes Zufferey. These are not only valuable as cultural assets, but also as a genetic reservoir. Their DNA could be the starting material for new breeds that are more resistant to diseases or better able to cope with the consequences of climate change. Sometimes nature takes action here.
Zufferey points to some Païen vines. He explains that there are special ecotypes that have arisen through spontaneous adaptation to locations. The plants show changes; the Agroscope researchers tracked them down in Valais vineyards and then cloned them. These crops actually responded differently to heat and drought, reports Zufferey. Evolution to look at, so to speak.
It’s not that experts don’t have enough ideas on how to tackle climate change. New plantings of warmth-loving vines are a solution, says Vivian Zufferey. However, the consumer often demands established varieties and has difficulties with still unknown plants.
Winegrowers have to react in good time
That is why they are also experimenting with Mediterranean rootstocks, says the expert. To protect against phylloxera infestation, when propagating vines, the fruit-bearing parts of the plant – of well-known varieties in this country – are connected to a phylloxera-resistant substrate, i.e. root stem, until both form a unit. Experts call this grafting. If a popular noble variety like the Chasselas is planted on a southern rootstock, the resulting vine should also be more resistant to drought.
In addition, modern irrigation techniques can help. However, the highly efficient drip irrigation system in Valais has hardly been used at all up to now. In any case, the conversion of viticulture will still require a great deal of investment, concludes Vivian Zufferey. It is unclear whether most winegrowers reacted in time. “We may already be too late.” Hopefully not.