Cornelis (Kees) van Leeuwen: winegrowers must adapt to climate change

The effects of climate change on vines are one of the research topics of Cornelis (Kees) van Leeuwen, a teacher-researcher at Bordeaux Sciences Agro. He studies in particular the impact on vines and the ways in which winegrowers are adapting to the changing climate. We asked him a few questions.

Cornelis (Kees) van Leeuwen is a professor of viticulture and a researcher at Bordeaux Sciences Agro and ISVV (Institute of Vine and Wine Sciences). His research focuses on the concept of terroir in winegrowing.

This reputed professor is driven by a passion for understanding the factors (soil, climate) that influence the composition of grapes and wine quality. He also studies the impact of climate change on viticulture and the adaptations that are necessary to produce good-quality wines in a changing environment.

Bordeaux Sciences Agro: what is considered a quality wine?

Cornelis (Kees) van Leeuwen: wine quality is a subjective concept. A quality wine is one that is a pleasure to drink and has well-balanced aromas and flavours. Besides this idea of quality, there is also, more importantly, a notion of typicality with regard to the place where the vine was cultivated, i.e. the terroir (the soil and climate). This latter element produces an extraordinarily diverse range of wines.

I believe that the typicality and originality of the wine are the most important: a great wine must possess a certain originality and ideally be instantly recognisable.

We can draw a parallel with the art world. There are thousands of painters, but when we see a painting by Monet, for example, we can instantly recognise it even if we have never seen it before because it has a particular style.

Wine typicality is determined by a combination of factors:

• The soil, which is unchanging
• The climate conditions which vary from one year to another but have defining characteristics in a given location
• The human factor determined by the winegrower’s choices (grape varieties planted, farming techniques, soil treatment etc.)

My research revolves around this question of quality, originality and typicality. Behind all that, there is the idea of promoting it. You would hope to sell a good wine for more money. There is an economic reality. It is a way of creating added value.

How do you make good wine?

You can make good wine when you understand how the climate and soil work to give the grape a specific composition in a particular location. Some of the winegrower’s choices (grape variety, farming techniques etc.) also affect the result. Decisions are made according to the soil and the local climate in order to produce a high-quality, typical wine.

How does climate change influence vines?

It is acknowledged within the community of researchers that the climate influences the quality and typical character of wine. The vintage is irrefutable proof of this. Climate conditions vary each year. You obtain different quality vintages depending on the weather in a given year.

Climate change also affects the composition of grapes and the wine. If the grape composition is different, the taste of the wine changes.

Climate change also modifies the resources used. In order to continue producing good wine, production processes have to be adapted by using different grape varieties, techniques etc. Winegrowers have to make different choices in terms of plant material and cultivation techniques.

Climate change does not prevent the production of great wine, but it will certainly have a different taste. Winegrowers must adapt to this change. My research aims to understand the effect of global warming on grapes and the taste of wine. We can then plan for the future and provide for adaptations to be put in place to continue making the best wine possible.

What are winegrowers doing to fight the effects of climate change in France and across the world?

Winegrowers have always adapted to climate conditions. The decision of when to harvest depends on the weather during that season. In hot years, they harvest earlier.

They can also cultivate the vines differently. Leaf stripping was once a commonly used technique. Today it is less so to prevent the grapes from getting too hot in the sun.

We are also seeing changes in the grape varieties used. Some grape varieties, like Sauvignon Blanc and Merlot, are not well adapted to high temperatures. Cabernet Franc and Cabernet-Sauvignon are better adapted to global warming. Petit Verdot also grows well in hot climates. It remains in the minority but its surface area has doubled in the Bordeaux region. We must therefore rethink the proportions of grape varieties in Bordeaux in the context of warmer temperatures.

New winemaking regions are appearing with global warming. Although it is early days still, we are seeing projects to plant vineyards emerging in Britany and Normandy.

Across the Channel, thousands of hectares of vines have been planted in recent years. England is becoming a serious wine producer as a direct consequence of global warming.

In the Mediterranean region, in Cyprus for example, vineyards are being planted at higher altitudes – at 1,400m – in search of cooler temperatures. In Argentina, vines are also moving to greater altitudes in the Andes.

Water resources are also becoming a challenge, with an increase in rainfall in northern Europe and a decrease in the Mediterranean area. Although the lack of water does not affect quality, it greatly reduces yields. Wine is better in dry years. You can grow vines with or without irrigation. Since it is necessary to preserve water resources, I am notably studying how to make wine using as little water as possible.

See the researcher’s profile on the following website
See also: « The new challenges facing winegrowing companies »