New grape varieties can help Bordeaux adapt to climate change, but will the market allow it?

By Professor Gregory Gambetta

Diverse biological systems are much, much more resilient to perturbation. This is true for ecosystems, but also for agricultural systems, including winegrowing.

History teaches the dangers of a lack of diversity. It is the 1980s and the California wine industry is booming, having doubled its vineyard surface area over the previous decade. Growers had been increasingly planting vineyards on a new rootstock promoted by UC Davis, named AxR#1 – used in 60-70% of the vineyards planted in Napa and Sonoma Valleys from 1960-1980. Unknown to growers at the time this rootstock was highly susceptible to a particular strain of the root-feeding insect phylloxera. So when phylloxera (also known as biotype B) spread throughout California it decimated all vineyards planted on AxR#1. The exact cost of this catastrophe is still obscure, but it ranges in the tens of billions of dollars. The moral of this story is clear; don’t put all your eggs in one basket.

Climate chaos
Today, the threat of climate change is increasingly present in winegrowing, and the industry knows that varietal diversity is an important lever in adapting to this change. For context it is important to remember that nearly all winegrape varieties are derived from a single grapevine species, Vitis vinifera, and this species is susceptible to a variety of pests (such as phylloxera, fungal pathogens, etc.) that many other Vitis species are not. On the other hand, within this species there is enormous varietal diversity, with more than 1,000 varieties.

Unfortunately, only a tiny proportion of this diversity is utilised in the global market. Just 11 varieties (Cabernet-Sauvignon, Chasselas, Chardonnay, Grenache, Merlot, Monastrell or Mourvèdre, Pinot Noir, Riesling, Sauvignon Blanc, Syrah, and Ugni Blanc) are responsible for more than a third of global production. And in many important winegrowing countries such as Australia, Chile, France, New Zealand, Switzerland, and the United States these varieties make up 64 to 87% of production. Furthermore, global trends over the past decades have been moving in the wrong direction, towards decreasing diversity.

Taming Merlot: ‘the problem child’
When the subject of varietal diversity and climate change is brought up here in Bordeaux there is one subject that comes up again and again; Merlot, the problem child of climate change. Because Merlot ripens earlier in the season growers in Bordeaux feel that it will be disproportionately affected by a warming climate. The chief concern is that Merlot grapes will become overripe, leading to higher alcohol wines that are not part of the Bordeaux identity. Many estates discuss decreasing their dependence on Merlot by moving to a higher percentage of Cabernet Sauvignon in their wines for example.

However, when we examine the past 20 years of red varietal evolution from Bordeaux (latest data available is 2020; courtesy of the CIVB) we see that the surface area planted to Merlot has not decreased, but instead has remained stable (left). During the same time the surface area of Cabernet Sauvignon and Cabernet Franc has declined (left), thus Merlot is making up a higher and higher percentage of the total surface area (right). Not surprisingly non-AOC designated varieties make up <1% of the surface area in Bordeaux, a figure that has not changed over the past 20 years.

So what explains this disconnect between the popular belief regarding Merlot and the reality on the ground? The simplest explanation would be time. Varietal evolution will be slow because vineyards are perennial systems that are designed to last decades.

However, the data on the ground doesn’t entirely support that explanation. Concerns about climate change, and Merlot in particular, are not new in Bordeaux and popular press accounts go back at least a decade, during which time the surface area of Merlot has slightly increased.

Some alternative explanations should be considered. One is that the concerns regarding Merlot are simply not being realised on the ground to an extent that would motivate change. This is probably due in part to grower adaptation, but equally it could be the changes are simply being tolerated. Being a plant biologist I know that most grapevine varietals are highly adaptable to a range of climates well beyond their traditional old-world ranges.

So are we talking about changes in wine style, and not (at least not yet) the life or death of specific grape vines? Or should we instead be worrying about the lack of urgency? As an industry do we just wait until a variety really falls off the cliff in a region before we truly consider change?

Market forces
Maybe one of the most important questions surrounding this discussion is this: will the market allow varietal evolution? From the market perspective perhaps a change in the ripeness level of Merlot is a much more tolerable change than switching varietals altogether? This doesn’t make good fodder for alarmist headlines, but I think we can consider it as highly plausible. Regardless, history does suggest varietal change is possible even for regions as steeped in tradition as Bordeaux.

New varieties
The recent approval of the six new varieties is rightfully lauded and represents an important step forward. However, it is important to be grounded about the potential magnitude of this change. The new varieties are currently limited to 10% of the finished wine volume for the Bordeaux and Bordeaux Supérieur AOCs.

Using the most recent figures from France AgriMer from 2019, even if those varieties were maximized at the full 10% for both Bordeaux and Bordeaux Supérieur, this would represent only 6% of the total wine volume produced by all Bordeaux AOCs. That means the proportion of current varieties would drop from 99 to 94%. This is not a significant change.

In the short-term we should consider a scenario where the market is so rigid and inflexible that it just won’t evolve or that the evolution will be too slow. Thankfully there are many other levers winegrowers can use in Bordeaux, and elsewhere, to adapt to a warming climate that do not involve changing varieties. Some are applicable over the short-term, like using canopy management and/or other strategies to decrease the temperature in the fruit. Others are more challenging and involve changing the way vineyards are planted (such as changing planting density, trellising systems, and/or rootstocks).

We need to be serious about varietal evolution because over the long-term increased diversity is one of our best tools to adapt to climate change, but we also need to be realistic about the speed at which varietal evolution can be realised, in vineyards and the marketplace. For now, there are more questions than answers.

 

Gregory Gambetta is professor of viticulture working as part of both Bordeaux Sciences Agro and the Institut des Sciences de la Vigne et du Vin. You can read his piece on Global Warming and Wine Quality: are we close to the tipping point? here.

With thanks to Familia Torres for the opening image.