Climate change and viticultureMedia-Workshop "Communicating on Climate Change"

Università degli Studi di Scienze Gastronomiche, Pollenzo - Bra (CN)

2017Maurizio Gily

Tavg: averagetemperature of the growing season April-Octoberperiod 1950-2000

Tstd: standard deviation

Jones, 2005

future prospection, 1999-2049

Tavg: averagetemperature of the growing season April-October

Tstd: standard deviation

Jones, 2005

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

BIOCLIMATIC INDEXESPurpose: 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

Region/Class °F Units °C Units General Ripening Capability and Wine Style

Region Ia 1500-2000 850-1111Only very early ripening varieties achieve high quality, mostly

hybrid grape varieties and some V. vinifera.

Region Ib 2000-2500 1111-1389Only 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 1389-1667Early and mid-season table wine varieties will produce good

quality wines. Alta Langa (Piedmont), Val di Cembra (Trentino),

Burgundy (F)

Region III 3000-3500 1667-1944Favorable 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 1944-2222Favorable for high production, but acceptable table wine quality

at best. Chianti (low altitude), Langhe (warm season) Barossa

(Australia)

Region V 4000-4900 2222-2700Typically 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…)

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)…

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 mainlybased 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?

Some Barolo «crus»

FromAlessandro Masnaghetti

Old wisdom: «Before buying a vineyard, watchwhere the snowmelts earlier»Still good?

Burgundy crus, a scheme

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

Other factors have influenced the rising in alcohol:clonal selection, «virus cleaning» of the varieties, probablyincreasing CO2 concentration in the atmosphere.

With the increase of CO2 in the atmosphere, even the leavesphotosynthesis 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 meansmore sugar in the fruit

In several vineyards the drought risk is increasedby the soil’s loss of water store capacity. Causes:

• erosion, that makes shallower the active layerof soil in the hillsides, where most of the qualitywines are made;• loss of organic substance, then the humiccolloids that favor the porosity of the soil and therefore the water storage;• compaction caused by the passage of heavymachines.

The trend has been underway for decades: for a sustainable viticulture it is absolutely necessary to reverse it.

WHAT TO DO?

Moving viticulture, where possible, towards higher altitudes, or choosing a differentexposure 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 crossingwith 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.

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 Mediteraneanvarieties have a different behaviour.

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 ison the border line, Southern Itay is out! (unless vineyards in altitude, Irpinia or Etna for example)

BUT: the authors considered Northerngrape varieties, not accustomed to warmer regions!

B=budburst (germogliamento) V=veraison (invaiatura)F=flowering (fioritura)H=harvest (vendemmia)

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 shouldnot have all the water that it requires while growing, in nature, on the banksof 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 stressfulconditions 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.

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 winevocation 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 vineto 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 slowlyto the roots, will help a lot.

SCANDAL!

Finally, some assumptions on which we are working, to counteract an excessof 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).

In conclusion, the viticulture has some means to counteract the effects of global warming, thanks to the adaptability of the plant and the possibilityof 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’simpact on this global phenomenon is not so important compared with other productions and activities. VICTIM more than responsible.