Faced with climate change 4 ways to save the Var vineyards from the heat stroke

What is the problem?

A Provençal vineyard threatened with extinction by 2050, this is the grim prediction made by Yves Leers, author of the book Wine, the great upheaval which investigates the effects of global warming. “I will be less alarmistemphasizes Nathalie Ollat, director of research within a cutting-edge unit* on wine at the National Research Institute for Agriculture, Food and the Environment (Inrae) in Bordeaux. Even if we think that years like 2022, combining drought and high temperatures, will multiply, the Var vineyards have a great capacity to adapt. Cultivation practices will have to change.”

Because the eccentricities of the weather have direct effects on the vine. Unequal depending on the areas of the territory, the drought this summer hit some corners of the Var hard, there breaking records like in Fréjus.

The ricochet effect of the rise in temperatures is the early development of the vine in the year which exposes it to significant damage during episodes of spring frost and the multiplication of extreme episodes such as hailstorms”. Nathalie Ollat.

“Overall, what we are currently observing are smaller grape berries, so a little less juice and that is really linked to the climate. Because the enlargement of the berry is done in two stages: a phase of multiplication of cells before veraison [moment où le grain se ramollit et change de couleur] and a cell filling phase during maturation. In the Var, we had rain after veraison, on August 15, and that allowed the berries to be a little overflowing, which were smaller, even if some areas had had rain at the end of June or even at Easter.”explains Constance Cunty, water management specialist at the Vidauban rosé wine research and experimentation centre.

As for the hot weather, “they modify the balance of the tastes of wines by concentrating them in sugar, by degrading one of the acids and can raise alcohol levels. It is also for this reason that we harvested so early this year, adds Nathalie Pouzalgae. She is the grape variety and aroma project manager in the same center which carries out numerous maturity checks in the lab to best adjust the date of the harvest and is actively working on solutions for the future.

*Ecophysiology and functional genomics of the vine unit.

The vine fetches water from deep in the ground. Infographic Aurélie Selvi.

Fetch water deeper in the ground

“We rarely see vines dying of thirst naturally”, entry pose Nathalie Ollat. Because if there is a positive element in this delicate equation of global warming, it is the generally resistant character of the vine, “a plant born in the Mediterranean basin, which, if the soil is deep, can draw water from several meters underground, without really watering”.

But with the drought, this water and certain minerals are buried further and further. A problem, especially for young vines whose roots are not very deep. Small mushrooms could then come to the rescue of the plant.

To boost the capacities of the roots of the vine, the rosé center has been exploring mycorrhization for a year. “It is an association between fungi present in the soil and the roots of the vine that we are currently testing on an estate in the Var, in partnership with the Nice start-up Mycophyto”says Constance Cunty.

How it works? By taking “mycorrhizae” from the foot of the test vine, these famous fungi naturally present underground, multiplying them in the lab and then reinjecting them in larger quantities into the soil to create kinds of super roots capable of going their market deeper in the earth.

The process, already used in agriculture, will have to be tested for some time “before we can report results”we say in the center of the rosé.

The roots of the vine reach a depth of several meters from 7 years. Istock illustration.

Adapt the plant by testing resistant grape varieties

This is the option on which the Var vineyards are the most advanced. Since 2019, the Center du Rosé has been supporting around ten winegrowers in another experimental approach.

Code name: resistant grape varieties.

Winegrower in Cogolin, Pierre Audemard is one of the pioneers on this path. Before launching 4 years ago, the Varois tasted wines produced in Germany, Switzerland, went to Italian nurseries, and integrated muscaris and floréal grape varieties on a small part of its exploitation, above all to test its resistance to vine diseases and limit the use of polluting treatments.

And it works: “The result is great!”

“My grape varieties have a real resistance to mildew and powdery mildew, I have reduced sulphating by 90 to 100% on these plots.”

Pierre Audemard

“With their high acidity, these grape varieties also counterbalance the lack of acids generated by warming and give more finesse and aromaticity to the wine”emphasizes Pierre Audemard.

Treating the plant less, or not at all, also means less damage to the state of the soil. With a positive ricochet effect in the fight against dryness: “the more living the soil, the better it retains water”explains hydroclimatologist Florence Habets.

A member of the study committee for the center du rosé, Pierre Audemard is now working to make his grape varieties even more resistant to heat.

“The main grape varieties we have in Provence are well suited to a Mediterranean climate, but we are trying to have complementary grape varieties in our range that will be even better suited to high temperatures, during the day but also at night. The goal, it is to anticipate the future”.

Nathalie Pouzalgae

To do this, the Center du Rosé teams planted five grape varieties from warmer and arid areas of the globe in May 2021 on their test plot: 3 Greek, 1 Spanish and 1 from southern Italy. Varieties that can be tested by winegrowers.

“The specifications of the Côte de Provence [leur] allowing them to plant 5% of their experimental varieties”, specifies the Center du Rosé. Authorized only for “vins de pays”, resistant grape varieties are not currently allowed in “AOC”.

At Domaine de la Giscle, in Cogolin, Pierre Audemard has been testing resistant grape varieties since 2019. Archival photo Guillaume Aubertin.

Create shade

Hide these rays that I cannot see. This is the credo of this track, already explored in the Var lands. For 3 years, shade nets, placed on the vines most exposed to the sun, have been tested in the Var.

“We are starting to have interesting results, with a real reduction in the water stress suffered by the vine and a shift in maturity”
Constantius Cunty.

To create shade, agri-voltaism is a solution “under review” on certain plots, in particular with the help of the Aix-based start-up Ombrea. As in Rians, on the estate of Gautier Hugues, who opened two plots of his vineyard to this new technology.

“At the cultural level it’s better, especially for the drought. We have 1°C less under the sheltered vines and we wait another week to harvest”he already confided during the 2021 harvest.

The idea: to shade the vines by sheltering them with solar panels, which can also be taken advantage of. “This type of experimentation lasts about 5 years, after which we can give a scientific evaluation. There are still many questions about the adaptation of these panels in the landscape, particularly with regard to the preservation constraints implied by the PDO”we qualify at the Center du Rosé.

In Rians, Gautier Hugues opened two plots of his vineyard to this new technology. FM/Var-Matin archive photo.

Move the vineyards to the heights

In the autonomous province of Trento, located in the North-East of Italy, the solution of moving is not a sweet utopia to avoid heatstroke. “Forty-five years ago, when we started, we planted Pinot Noir at 350 meters, an altitude that offered ideal conditions for this variety. Today, we are moving it to 650 meters”confides a transalpine winegrower to the weekly The Essenzialerelayed by The International Courier from September 1.

Yes, the vineyard instead of being installed in the plain, could go up in altitude, to benefit from cooler temperatures

This is confirmed by wine expert Nathalie Ollat, who considers the option relevant especially for vineyards that already have unexploited hills.

For a department like the Var which has foothills, it is a track whose feasibility must be checked.

“In the hinterland of Montpellier, vineyards have thus settled on the Larzac plateau [dont l’altitude est comprise entre 600 et 900 mètres]she adds.

The pitfall: the return to more traditional viticulture, with, for example, cultivation on terraces, which is more labour-intensive. “We are working on other adaptation levers for the moment but why not study this option one day”we react to the Center du Rosé.

Faced with climate change 4 ways to save the Var vineyards from the heat stroke