After the frost, after the hail, Drought and heat wave. Even if it is announced to be of good standing, the 2022 vintage has not been easy for the 60,000 French estates. “The vine is a plant adapted to heat, but when the drought is prolonged, it becomes fragile”, explains Benjamin Bois, teacher-researcher at the University Institute of Vine and Wine (Dijon). Beyond a certain limit (around 37°C), summer damage is devastating. Thus, in July 2019, the grapes and the leaves had been literally burned by the sun. For these 2022 harvests, the essentials have been saved, but the economic equation becomes more complex each year. “In 2021, due to frost, we lost almost the entire harvest,” says Eric Coulon, owner of Roger Coulon champagne. Farms must adapt to a climate that has gone crazy, which weighs on the maturity of the grapes, and therefore on their operating costs. So the domains try to adapt, as they can.
In recent years, requests for derogations have multiplied in order to irrigate the vines, a practice that was prohibited for a long time. Yet many believe this is the worst solution, since there is less and less water available for agriculture. “Changing our management of the vine is more effective”, assures Nicolas Ravel, vineyard manager at the Cave de Tain (northern Rhône). Example: the cooperative now leaves fewer bunches of grapes on each vine stock. Crozes-Hermitage thus no longer keeps its seventh “emergency” cluster (if one of the six others is not ripe enough). Result, less water consumed by the vine, since there is less fruit to feed.
Limit water loss
For the soil, the same fight: the Cave de Tain is starting to leave “grassed” only one in two rows. Grass is organic, but it consumes water! “We also bring more organic matter to the soil, this has a cost, but the water retention is much better”, explains Nicolas Ravel. On the Provence side, at the organic domain of Cala, we have to get the tractors to pass again to dig deeper (70 cm) between the rows in order to better capture the precipitation. “It’s more manual work, like going organic, so additional costs,” notes its manager Flavian Maison.
The vine looks like us: it sweats. To avoid this loss of water, more and more professionals prune the upper parts of the foliage. “Another advantage: it slows down the ripening of the grapes, a ripening that is constantly accelerated by global warming”, specifies Benjamin Bois.
Before flowering (from April), the vines can also be pruned differently. “With global warming, we paradoxically have more spring frosts, we now prune the plots most vulnerable to the cold as late as possible”, explains Damien Champy, president of the Lebrun de Neuville cooperative (Champagne). Some northern winegrowers are also inspired by southern practices. “One of the avenues I’m looking at is the ‘bush’ pruning, with arms that fall to the ground and better protect the grapes, and the soil from the sun’s rays”, indicates Eric Coulon, who also explains pruning “shorter”. (and therefore have fewer arms).
The shadow is the Grail. Estates such as Le Puy (Bordelais) have therefore been testing “pergola” management for three years: vines carried up high and forming a green roof. A wine tradition dating back to the dawn of time in hot countries. This involves harvesting the grapes manually, as in all grand crus. For current wines, this technique is difficult to mechanise, and therefore not profitable.
Replant trees to shade the vines
Another track: “agroforestry”, which consists of replanting trees in a vineyard to shade it. At Champagne Roger Coulon, we assure you that this lowers the temperature on the ground by 5 to 6°C! More shade generates less soil temperature, which promotes microbial life, and therefore water retention. CQFD. Some southern vineyards are experimenting with a more surprising way: “agrovoltaism”. In the Vaucluse, reversible voltaic panels have been installed above the vines with the help of INRAE. The idea? Use it as a parasol to protect the vines from water stress in very hot weather while generating energy production. Clever… except when it comes to landscape.
For several decades, the dates of the harvests have not ceased to advance. the global warming indeed accelerates the growth of the grape. We now harvest at the beginning of September or at the end of August and sometimes even in mid-August! Formidable for freshly harvested grapes, fragile products that cannot be stored for too long in heavy air. Californian winegrowers, victims of terrible heat, solved the problem by harvesting at night, from 3 a.m. to 10 a.m. In Champagne, the interprofession is also mobilizing: “We strongly encourage our members to deliver the grapes to the cellar as quickly as possible”, explains Damien Champy (Le Brun de Neuville). The cooperative also advises them to use crates… of white color – far from being a gimmick, this can lower the temperature of the grapes by several degrees compared to a dark box. It is also in full reflection to finance the repair of its pressing center and to air-condition its reception quay. A paradox at a time when air conditioning, which is particularly energy-intensive, is beginning to be heavily regulated. The organization is also examining the possibility of cooling its stainless steel reception tanks, but hesitates because this also means increasing its carbon footprint.
A new climate, new oenological practices
Another avenue for adapting to global warming is that of adapting oenological practices. They bear the charming names of Ionys and Laktia and have been experienced for two years at the Cave de Tain. They ? New “acidifying” yeasts, capable of acting on the degree of alcohol (by containing it) and the acidity of the juice (by increasing it). Objective: to obtain balanced whites and reds from the northern Rhône, which remain below 15°. “Another solution is to dealcoholise the juices, but our first attempts are not very conclusive”, explains Xavier Frouin, chief oenologist at the Cave de Tain. All these tests weigh on the budgets of the cooperative, but they are essential: the debate is indeed raging on the excessively high degrees of alcohol obtained in the Rhone Valley. One of the major local players, Michel Chapoutier, recently electrified the discussion by proposing, on an experimental basis, to lengthen the juices that are too heavy with a little water!
At the same time, estate owners are rethinking the stock of grape varieties. Pinot Noir is no longer king in Burgundy. The famous region is working on authorizing the cultivation of Syrah, very much identified with the vineyards of the South. One estate (Millot) caused a sensation by planting a quarter of a hectare. Throughout France, the map of traditional grape varieties is changing. “The evolution of plant material is one of the keys to the future”, confirms Benjamin Bois. Species of vines naturally resistant to high temperatures, such as Mourvèdre or Grenache (both from Spain), are rare. Most of the others will “migrate”: Alsace plants Syrah, the Loire Merlot, and Bordeaux has just authorized (in the AOC specifications) the cultivation of the powerful Touriga Nacional, one of the constituent grape varieties of Port, in the very arid Douro Valley (Portugal). The Greek xinisteri grape variety is also tested in the Graves.
For its part, Champagne is resuscitating its ancestral arbane and petit meslier (a specialty of the family producer Drappier), very interesting species because they ripen very late (which therefore do not risk being harvested during the hottest weather). Sometimes, it is a variety created from scratch to be resistant that is launched, such as voltis, created in the laboratories of Inrae, tested in Champagne for ten years, in the process of authorization by the Inao. The climate is changing, the France of wine too.