If only a few years ago some winegrowers were still doubtful about global warming, today, the whole profession has become aware of the phenomenon and climate change is now in everyone's mind. Vineyards and agriculture in general are in the forefront. Forced to adapt, the winegrowers laid the foundations for new working strategies.
Climate change, global warming, adaptation..., all these terms flourish in reports, congresses, working groups, conferences, and the entire supply chain, from winegrowers to institutions, is now aware of the problem. It is impossible to ignore it after the extreme weather episodes of recent years that have destroyed several harvests and significantly modified the intrinsic characteristics of the wines. Early harvests, high alcoholic degrees, significant decrease in acidity, floods, storms, hail, spring frosts, droughts have marked the last 3 vintages.
When temperatures are too high, maturations are blocked. Winegrowers are therefore working more and more on the scale of the vines in order to lower the temperatures of the berries. In the south of France, winegrowers are reducing or even eliminating leaf thinning in order to protect the grapes from the sun through foliage. In Burgundy, where humidity is high, winegrowers prefer to increase the height of the trimming (an operation that consists in pruning the end of the oaths).
Because "global warming does not mean good weather," says Ludivine Griveau, director of the Hospices de Beaunes in Burgundy, in an interview for Bourgogne Aujourd'hui. Indeed, Burgundy has to face higher temperatures while keeping a high humidity, increasing parasitic pressure.
Water availability will be the major challenge in the coming years, as a brutal consequence of climate change. Rainfall episodes are more powerful and less well distributed over the year. They often cause damage and are insufficient in the face of summer droughts. Winegrowers are reappropriating farming techniques that help to drain the soil better, limit erosion and fill groundwater tables.
Grass cover in the vines is a theme that is increasingly studied in research centres and increasingly practiced by winegrowers. Grassing helps to strengthen biodiversity, protect the soil and keep a certain amount of moisture at the scale of the vines. In Languedoc, where the drought is very severe in summer, weeding between rows avoids competition from grass on the vine for water.
The question of de facto irrigation is increasingly raised in vineyards. Will it one day become essential to continue producing quality wines? Or will water constraints make this solution obsolete even before it is really raised in the debates? Looking beyond our borders, irrigation, while it has helped the development of vines in the provinces of Mendoza (Argentina) or California (United States), does not solve the wine problem of global warming in these regions, nor does it provide answers to the lack of water.
Well aware of this contradiction, the IFV (Institut Français de la Vigne et du Vin) focuses its research on varietal improvement and rootstock selection in order to offer winegrowers varieties with better water resistance. Moreover, the winegrowers did not wait for the results of this research to examine the varietal adaptation of their plots, favouring more water-efficient varieties that adapt to higher temperatures.
The latest vintages attest to this: alcoholic degrees rise, acidities fall and it is not easy for oenologists to maintain a good balance. A look at the wine product catalogues confirms this trend. Yeasts that limit alcohol production and/or increase acidity in wines are increasingly being offered as a solution to winemakers. The winegrowers also play on the length of maceration to balance the wines, slightly but fairly easily modifying the oenological processes, as Ludivine Griveau explains: "A slightly longer maceration before it ferments in red, to get the maximum of aromas [...] Then, a shorter alcoholic fermentation, the alcohol which comes out more slowly, silkier extracted tannins".
It is a verse that is sometimes heard: vineyards move north, a godsend for some regions at the expense of the southerners. Professor Monika Christmann, director of the University of Geisenheim, Germany, reports that global warming, initially positive for German vineyards, is "now proving to be too much". Moreover, "while summers are more and more favourable to wines, they are also more and more chaotic and winegrowers have to face climatic accidents".