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Climate change and viticulture


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Some data and some reflections about the impact of the global warming on wine production, wine geography and wine quality. And how to counteract the negative effects.

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Climate change and viticulture

  1. 1. Climate change and viticulture Media-Workshop "Communicating on Climate Change" Università degli Studi di Scienze Gastronomiche, Pollenzo - Bra (CN) 2017 Maurizio Gily
  2. 2. Tavg: average temperature of the growing season April-October period 1950-2000 Tstd: standard deviation Jones, 2005
  3. 3. future prospection, 1999-2049 Tavg: average temperature of the growing season April- October Tstd: standard deviation Jones, 2005
  4. 4. Burgundy: harvest beginning, days before or after August 31 in the last 7 centuries. Emmanuel Le Roy Ladurie Valérie Daux Jürg Luterbacher, Le climat de Bourgogne et d'ailleurs (XIVe-XXe siècle) , Histoire, économie et société Année 2006
  5. 5. BIOCLIMATIC INDEXES Purpose: To describe the climate of a country or “terroir”, or the climate of a certain year, by means of numerical, and therefore precise, parameters Winkler or degree day (DD) The index of Amerine & Winkler is a figure given by the sum of all daily average temperature from 1th April to 31th October that are over 10 °C or 50°F: if a daily temperature is under that threshold it is not considered in the sum. This is because this threshold is considered the limit for the vine to grow. The index formula is the following one: IW = Σ [(Tmax+Tmin/2) —10] 1 Apr – 31 Oct (N.H.) Winkler: Sum of average daily T (calculated as (T minimum+Tmaximum)/2 ) higher than 10 °C or 50 °F from April 1 to October 31 Amerine e Winkler, Davis University 1944
  6. 6. Region/Class °F Units °C Units General Ripening Capability and Wine Style Region Ia 1500-2000 850-1111 Only very early ripening varieties achieve high quality, mostly hybrid grape varieties and some V. vinifera. Region Ib 2000-2500 1111-1389 Only early ripening varieties achieve high quality, some hybrid grape varieties but mostly V. vinifera. Morgex (Valle d’Aosta), Mosel (Germany), Champagne (France) Region II 2500-3000 1389-1667 Early and mid-season table wine varieties will produce good quality wines. Alta Langa (Piedmont), Val di Cembra (Trentino), Burgundy (F) Region III 3000-3500 1667-1944 Favorable for high production of standard to good quality table wines. Langhe, Monferrato (Piedmont), Mount Etna (Sicily), Napa (USA) Bordeaux (F), Eden Valley (Australia) Region IV 3500-4000 1944-2222 Favorable for high production, but acceptable table wine quality at best. Chianti (low altitude), Langhe (warm season) Barossa (Australia) Region V 4000-4900 2222-2700 Typically only suitable for extremely high production, fair quality table wine or table grape varieties destined for early season consumption are grown (Italians don’t agree!). Apulia, Sicily DD Winkler index climatic regions classification (Italians don’t agree with last cell evaluations…)
  7. 7. Courtesy of Federico Spanna, Regione Piemonte, Servizio Agrometeorologico 0 500 1000 1500 2000 2500 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 La Morra (CN) Degree days > 10 °C (Winkler) Shifting from Region III to Region IV (Winkler)…
  8. 8. Piemonte: Are the so called “sorì” (more sunny slopes) still the best places for viticulture? The climate change tends to break the scheme. Qualified experts propose a Barolo hierarchy mainly based on sun exposure. But, while the shooter is firing, the target is moving! What about the concept of “premier cru”? Is it moving toward cooler expositions?What about the concept of “premier cru”? Is it moving toward cooler expositions?
  9. 9. Some Barolo «crus» From Alessandro Masnaghetti Old wisdom: «Before buying a vineyard, watch where the snow melts earlier» Still good?
  10. 10. Burgundy crus, a scheme
  11. 11. Climate/terroir/time of harvesting and wine characteristcs cool climate or early harvest hot climate or late harvest acidity alcohol color green, rough tannins dens, silty tannins green flavors ripen fruit flavors time of harvest, temperate climate August 15 November 30
  12. 12. Other factors have influenced the rising in alcohol: clonal selection, «virus cleaning» of the varieties, probably increasing CO2 concentration in the atmosphere. With the increase of CO2 in the atmosphere, even the leaves photosynthesis tend to increase, with CO2 capture: a side effect of greenhouse large emissions, that partially makes a compensation. More CO2 means more phosynthesis, more phosynthesis means more sugar in the fruit
  13. 13. In several vineyards the drought risk is increased by the soil’s loss of water store capacity. Causes: • erosion, that makes shallower the active layer of soil in the hillsides, where most of the quality wines are made; • loss of organic substance, then the humic colloids that favor the porosity of the soil and therefore the water storage; • compaction caused by the passage of heavy machines. The trend has been underway for decades: for a sustainable viticulture it is absolutely necessary to reverse it.
  14. 14. WHAT TO DO? Moving viticulture, where possible, towards higher altitudes, or choosing a different exposure than full South. In Europe, the viticulture is shifting northward. Viticulture in England: currently more than 2000 hectares. New vineyards in Denmark, Poland, Sweden. Not «pure Vitis vinifera» varieties are often planted, deriving from multiple crossing with Vitis amurensis, early ripening and resistant to mildew and powdery mildew. Interesting varieties for lowering the impact of pesticides, but, on the other side, a risk for the Mediterranean viticulture: a partial relocation of wine production in cooler and more rainy areas.
  15. 15. Cool climate=better wine? A large French and English bibliography assumes this paradigma. Italian, Spanish, Portuguese, don’t agree… The question is strictly related with the choice: indigenous/international varieties. No grape was born “international”! Any grape has an origin, and have been chosen and grown in a specific place. Usually it provides its best results in that place, or in similar places for climate and soil conditions. So the idea that Merlot or Cabernet can fit everywhere is wrong (to say nothing of the extremely demanding Pinot noir). Atlantic grapes, in absence of irrigation, show water stress and poor quality in every hot and dry season, while the Mediteranean varieties have a different behaviour.
  16. 16. According with a famous review of Jackson and Lombard (American Journal of Enology and Viticulture, 1993) the best wine is made in alpha climatic zone, that is where the average daily temperature during the ripening period doesn’t exceed 15°C. Centre of Italy is on the border line, Southern Itay is out! (unless vineyards in altitude, Irpinia or Etna for example) BUT: the authors considered Northern grape varieties, not accustomed to warmer regions! B=budburst (germogliamento) V=veraison (invaiatura) F=flowering (fioritura) H=harvest (vendemmia)
  17. 17. So the first rule is: respect a correct relationship environment/grape variety What’s terroir? The RDI irrigation, i.e. Regulated Deficit Irrigation, was invented in Australia and is based on the principle that, to give a quality wine, a vine plant should not have all the water that it requires while growing, in nature, on the banks of a river, but only a part of it. It‘s a restrictive diet regime, leading to a moderate stress (mild stress). Under the effect of slightly stressful conditions the plant accelerates the ripening of the fruit and the seed, to ensure the continuity of the species. But this stress shouldn’t be too severe.
  18. 18. What’s terroir? Most of classic European wine terroir are those in which, without irrigation, due to the right combination of climate and soil, the plant enters the moderate stress regime at the appropriate time. A fundamental character of the wine vocation of a territory is, therefore, a certain way of the water to move in the surface and in the middle layers of the soil. But the increase of extreme events can upset this "suitability" forcing the vine to too severe stress, with serious consequences on yield and quality. Improving the microbial and animal life of the soil and its organic content, and getting a better ability to retain water and nutrients and releasing them slowly to the roots, will help a lot.
  19. 19. SCANDAL! Finally, some assumptions on which we are working, to counteract an excess of alcohol and an unbalanced composition of a fruit too early ripen, go in a strange direction: exactly opposite to what has been proposed, in the past, to produce super-premium wines: • lower plant density and more buds per plant; • Fruit area position higher from the ground and partially shaded; • reduction of the ratio leaves / fruits with a targeted canopy manipulation (subtraction of photosynthetic surface).
  20. 20. In conclusion, the viticulture has some means to counteract the effects of global warming, thanks to the adaptability of the plant and the possibility of partially manage its physiology. Nevertheless, the warming of the climate is seriously concerning the growers, who are involved in the battle to reduce at least the anthropogenic component of global warming linked to greenhouse gas emissions. There are many experiences regarding this in the vineyard and in the winery, that we have no time to deal with: anyway the wine production’s impact on this global phenomenon is not so important compared with other productions and activities. VICTIM more than responsible.