Vignes & Climat
π Planet
Wine industry: a sector evolving in the face of climate change?

The new flavours of global warming wine

Clément Boulle, Executive director of Polytechnique Insights
On March 18th, 2021 |
3 min reading time
Alexandre Pons
Alexandre Pons
Œnologue for the Oeneo Group and Institut des sciences de la vigne et du vin
Philippe Darriet
Philippe Darriet
Professor of oenology and director of the Oenology Research Unit (associated with INRAE) at Institut des sciences de la Vigne et du Vin
Key takeaways
  • Climate change is changing the aromas of wines: hints of fresh fruit (strawberry, blackcurrant) of Bordeaux wines are now closer to dried fruits (like prunes).
  • These wines are less acidic, sweeter and contain more alcohol.  Experts Alexandre Pons and Philippe Darriet are also concerned about long term conservation of these wines.
  • But, correcting these aromatic changes requires a step in the opposite direction of the cultural practices that have been implemented over the past twenty years, which will take time.
  • The challenge is to increase yields, reduce leaves, increase bunches and to reduce plantation density.

What are the con­se­quences of glob­al warm­ing on the aro­mas of wine?

Alexan­dre Pons. Since the 2000s, we have observed a change in the aro­mas of grapes and red wines as well as mod­i­fi­ca­tions in their matu­ri­ty. Some say that Bor­deaux wines have nev­er been this fine because their qual­i­ty is far more con­sis­tent. But it is clear that the aro­mas of fresh fruits (straw­ber­ry, black­cur­rant) con­tribut­ing to the sin­gu­lar­i­ty of these wines are giv­ing way to aro­mas of dried fruits (prune) which are more char­ac­ter­is­tic of south­ern regions.

Philippe Dar­ri­et. We should also note the atten­u­a­tion of plant char­ac­ter­is­tics, such as aro­mas of pea pods or fresh pep­pers. With glob­al warm­ing, aro­mas of stewed fruits, but also dry fruits and old wood, are brought out in the wines. They also seem heav­ier, con­trary to the his­tor­i­cal­ly-known Bor­deaux wines that were char­ac­terised by their fresh­ness, even after more than 10 years of ageing.

Why have the wines changed this way?

AP. Water (hydric) stress and ther­mal stress induce defence mech­a­nisms in the plant. This leads to the bio­chem­i­cal degra­da­tion of fat­ty acids. As a result, the pro­duc­tion of odor­ous volatile com­pounds, most often car­bonyl com­pounds, cre­ate these stewed fruit aro­mas found in the grape berry. In Bor­deaux, this is regard­ed as a flaw gen­er­al­ly found in pre­ma­ture­ly aged red wines.

PD. Sev­en­teen grams of sug­ar are required to pro­duce one degree of alco­hol. Grapes with a high­er pro­por­tion of sug­ar thus pro­duce wines with a high­er alco­hol con­tent. Yet the grapes need to be ripe to begin har­vest. Cor­rec­tive action like pre­ma­ture har­vests are lim­it­ed, espe­cial­ly in terms of the most sen­si­tive grape vari­eties such as Merlot.

Is the age­ing poten­tial of wines under threat?

AP. This is an impor­tant ques­tion. Giv­en the adap­tive poten­tial of humans and plants, if we do noth­ing, glob­al warm­ing will like­ly alter the age­ing poten­tial of Bor­deaux wines. At the moment, this is not a proven research result as this esti­ma­tion stems from a col­lec­tion of pre­lim­i­nary research results and a reflec­tion on the mod­i­fi­ca­tions of oeno­log­i­cal and cul­ti­va­tion prac­tices. What makes wine sta­ble from a micro­bi­o­log­i­cal point of view, is the pres­ence of alco­hol and acid­i­ty. How­ev­er, chem­i­cal mech­a­nisms – most of which are adjust­ed by the acid­i­ty lev­el of the envi­ron­ment – mod­i­fy the aro­mat­ic bal­ance of the wine dur­ing stor­age. And as it hap­pens, the degree of alco­hol has sig­nif­i­cant­ly increased these past 20 years while acid­i­ty has decreased. The very essence of the chal­lenge for wine­mak­ers is to man­age the matu­ri­ty of grapes, to lim­it their degree of alco­hol and to use tech­niques to pre­serve acidity.

Should we cor­rect this change?

AP. There are two per­spec­tives. The first aims to pro­duce pow­er­ful and whole-bod­ied wines. The sec­ond con­sid­ers that these are not the future of Bor­deaux because their aro­mas are too heavy and too rich in alco­hol. But it is not because we have a rise in aver­age tem­per­a­tures that we will nec­es­sar­i­ly have dif­fi­cul­ties in the upcom­ing years. The chal­lenge is to pro­duce fresh wines with grapes that are a lot riper than they were 20 years ago.

What can we do to achieve this?

AP. Dur­ing the 80s and 90s in Bor­deaux, oenol­o­gy strived to devel­op tools to ripen grapes. The aim was to reduce the veg­e­tal char­ac­ter­is­tics of wine. We reduced yields, car­ried out leaf-thin­ning to increase the amount of sun­shine on grape berries, decreased the load (the num­ber of bunch­es of grapes), den­si­fied plan­ta­tions and so forth.

Today, we need to reverse these cul­ti­va­tion tech­niques. We already see results of what hap­pens when these changes are imple­ment­ed. But we are ask­ing wine­mak­ers to do the exact oppo­site and drop out­dat­ed advice giv­en to them 20 years ago – so it takes time. Fur­ther­more, in the field we have not­ed that some wine­mak­ers have the desire to select vari­eties more adapt­ed to the local cli­mate. Yet it would be a mis­take to intro­duce emblem­at­ic grape vari­eties from oth­er great wine­mak­ing regions in the Bor­deaux vine­yards, even though they might be bet­ter suit­ed to the local climate! 

The Bor­deaux region holds a long-stand­ing wine­mak­ing tra­di­tion built on a great diver­si­ty of grape vari­eties, even if today they are reduced to the bare min­i­mum (only three red grape vari­eties are most­ly grown in Bor­deaux). Reviv­ing past vari­eties could help to broad­en the taste and aro­mat­ic palette of Bor­deaux wines while per­pet­u­at­ing the tra­di­tion­al high-qual­i­ty wine pro­duc­tion in the con­text of cli­mate change.

PD. The use of alter­na­tive vari­eties is a long-term move­ment, evi­denced by the his­to­ry of Bor­deaux vine­yards. With­out dis­card­ing out­side vari­eties, an increased pro­por­tion of oth­er grape vari­eties of the Caber­net fam­i­ly can be an adap­ta­tive solu­tion. In addi­tion, a first-rate selec­tion of root­stocks adapt­ed to severe hydric stress could also work. By imple­ment­ing prac­tices to lim­it the change of wines, oenol­o­gy is also capa­ble of bring­ing cor­rec­tive solutions.

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