The impact of climate change on wine growing
Thunderstorms, drought periods, forest fires: Climate change can be felt in almost all areas of life – and viticulture is no exception. Winegrowers need to adapt to new conditions, as the changes to climate and weather conditions have a direct impact on grapevines planted in vineyard parcels, sometimes even with serious consequences.
Not only are the direct effects of global warming measurable and in some cases visible, we can also see and feel them as people. The majority of us don’t notice gases in the air or changes in atmospheric composition in everyday lives; however, factors such as temperatures rising year-round, increased heavy rain one moment and extreme droughts the next are simply unavoidable – and have repercussions when it comes to wine growing.
The consequences for wine-growing regions
All of these changes have an enormous influence on wine growing – sometimes in the short term, but always in the medium and long term. On hillsides or steep slopes, heavy rainfalls can lead to rainwash, soil erosion and meters-deep ditches between the rows of grapevines. By contrast, unusually high temperatures of over 40 degrees Celsius and unimpeded sunshine can result in sunburn and drought damage to the leaves, grapes and berries, thus causing substantial harm. In 2015, together with the Julius Kühn-Institut and the Deutscher Wetterdienst (German Meteorological Service), the Federal Ministry for Food and Agriculture (BMEL) published a study on “extreme weather conditions relevant to agriculture and possible risk management systems.” The study reports that, while the effects of climate change are felt in the long term, extreme weather conditions in the short term, such as “heat, drought, flooding, hail or frost can do serious harm to agriculture and forestry.”
Suitability and demarcation of wine-growing terrain
Some of today’s wine-growing countries and regions have been around for centuries. The Greeks and later the Romans brought wine growing from Italy and spread the grapevine to every corner of Europe. Since then, grapes have been cultivated in the Champagne region of France, on the Moselle, in the Rhine valley and on the Danube, in the Douro valley in Portugal, on the Iberian plateau of La Mancha and beyond.
Most wine-growing regions have evolved historically and, due to economic and societal conditions, been designated as vineyards. Over the centuries, an entire legal system emerged, which exists today in the form of a legal superstructure of protected vineyard sites, areas and elaborate systems of cultivation and replanting.
A study into the wine industry by the University of British Columbia in Canada caused a sensation at the start of the year. It concluded that an average increase in global temperature of two degrees Celsius would mean losing more than half of the existing wine-growing lands. If the global temperature were to rise be 4 percent, the loss of current vineyards would amount to more than 75 percent.
For instance, wine grape varieties may only be planted on land that is suitable for wine growing. In addition to the direction and gradient of the slope, shielding from the horizon, exposure to the wind, risk of cold air and suitable soil conditions, climate plays a decisive role in whether grapes may be planted in a given region. Moreover, old, existing vineyards enjoy protected status.
In light of ongoing climate change, traditional wine growing is likely to change. This frequently raises the question of whether or not wine growing can continue in the same areas, using the same methods. To approach the climate phenomenon, we must first distinguish between three basic terms.
The Huglin index
Temperature, particularly the average daytime temperature, constitutes one of the central parameters of climate and is a critical indicator of where and how which plants and varieties can be cultivated and therefore plays a critical role when selecting a suitable grape variety for different temperature ranges. One of the best known methods for assessing a wine-growing region’s suitability for different grape varieties in terms of temperature compatibility is what is referred to as the Huglin index. The index is calculated from the daily average temperature and the maximum temperature for the period between April 1 and September 30.
A location with a long-term average value under 1,500 (Huglin index) is deemed unsuitable for grapes’ temperature requirements (see table below). Locations in the next section, with 1,500 to 1,600 points on the index, can be used to cultivate grapes with relatively low requirements, such as Müller-Thurgau, Kerner or Blauer Portugieser. At the other end of the scale are heat-loving grape varieties like Grenache, Syrah, Zinfandel, Carignan or Merlot. In general, red wine varieties are more heat tolerant, while white wines are better suited to cooler regions.
|Huglin index H||Selected cultivatable grape varieties|
|H < 1,500||Cultivation not recommended|
|1,500 < H < 1,600||Müller-Thurgau|
|1,600 < H < 1,700||Pinot blanc, Gamay noir|
|1,700 < H < 1,800||Riesling, Chardonnay, Sylvaner, Sauvignon blanc, Pinot noir|
|1,800 < H < 1,900||Cabernet franc|
|1,900 < H < 2,000||Chinon blanc, Cabernet Sauvignon, Merlot|
|2,000 < H < 2,100||Ugni blanc|
|2,100 < H < 2,200||Grenache, Syrah|
|2,200 < H < 2,300||Carignan|
|2,300 < H < 2,400||Aramon|
Table: Huglin index of selected grape varieties (Hoppmann, 2010).
Up to now, wine growing has hardly changed at all, at least when it comes to the cultivation of traditional grape varieties. That’s why Riesling remains the most important grape variety in Germany, while in Austria it’s the Grüner Veltliner, in Italy it’s the Sangiovese and for France, it’s still the Cabernet Sauvignon. Merlot, Grenache, Syrah, Carignan and Tempranillo are the most important grape varieties in the southern Mediterranean regions of France, Italy and Spain.
However, the temperature zones are shifting further north, which understandably raises the question: Will wine growing in Europe settle in more northern regions in future, and will Southern Europe soon become unsuitable for wine growing?
In addition to wine-growing regions migrating northward and up mountain slopes into cooler temperature ranges, which can already be seen in Trentino and South Tyrol, there is a different approach – replacing the existing grape varieties with different, more heat-resistant ones.
Outlook: switching to different grape varieties is an option
Many white wine regions could switch over to red wines, while current red wine regions could start planting more heat-loving varieties.
While this might reduce loss of land, it wouldn’t stop it altogether. Moreover, it remains to be seen whether the newly produced red wines would even attract the interest of buyers and consumers. Even when it comes to breeding newer, more heat-resistant grape varieties, the question of demand can’t be answered easily.
The use of rootstocks seems more promising, as they mature later and are more resistant to drought. The well-known grape varieties and traditional styles of wine could continue to be produced and marketed.
However, these strategies and solutions don’t provide an answer to the underlying challenge, which is that of reducing the rising global temperature and therefore actively lowering climate-damaging emissions.
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