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lundi, 07 décembre 2015

CLIMATIC CHANGES AND WINE (PART 2 OF 3)

CLIMATIC CHANGES: ADAPTATION IN THE VINEYARD


 

Claude Gilois 

 

MOVING VITICULTURE TO THE NORTH OR THE SOUTH DEPENDING ON THE HEMISPHERES

 

This solution, in theory, appears to be the simplest, but in practice and also for cultural reasons, it is far more complicated than it appears for several reasons. In Europe, more populated than the New World, vines have essentially been planted on poor soil (to keep it simple, vines do not like rich soil as they puts too much energy into the foliage and not enough into the grapes). In any case, rich soils were largely reserved for other culture in Europe where productivity is not a self-limiting factor for quality. In densely populated countries, it is not going to be easy to find suitable land for viticulture other than areas where it was developed over several hundred years. Additionally, some regions (Burgundy, Piedmont, Rhône) have succeeded in achieving such extraordinary association between, terroirs, climate, soil and grape varieties that it would be impossible to reproduce this adequately elsewhere. If vines can grow pretty much anywhere, they give best results on poor soils on slopes. Of course, a relocation of viticulture is already taking place, but on less prestigious terroirs. The Champagne houses have bought land in the UK to make effervescent wine, but Champagne up to recently, was a wine made principally in the cellar. Champagne made from exceptional terroirs will have to adapt as will  the rest of viticulture. It is very difficult to imagine that Syrah could replace pinot noir in Burgundy and Tempranillo could invade the northern Rhône. Relocation of vineyards might be easier in the New World, which has less of a driven terroir’s philosophy and large land surfaces suitable for viticulture such as in the USAs in Willamette Valley or the Okanakan Valley in Canada and in other states of the USA, in particular in the Washington states. However, certain countries of the New World will have much less facilities to move their viticulture as they are bordering oceans (South Africa and to a lesser extend Australia).

 

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THE DISPLACEMENT OF VITICULTURE IN ALTITUTE

 

Altitude displacement appears to be more realistic, whenever possible, for the best vineyards rather than their relocation according to latitudes. Slopes in altitude are particularly well adapted to viticulture as they provide better exposure and better drainage. Of course, it is easier   to plant on the flat rather and  in the Valley and in some region only slightly sloping land is utilized and the steeper slopes in many countries are underutilized (Napa valley, parts of France and  Spain). Wherever possible, it is a solution that growers in this situation must envisage. It will not be within causing problem is some growing regions. If we take for example Burgundy which classification is decomposed into three zones where the ‘Cotes’ makes the best wines, the flat attracts viticulture of lesser quality and makes lesser wines and the ‘Hautes Côtes’ which produce more supple wines, but  sometimes  with great complexity.

Could wines from the ‘Hautes Côtes’ compete with wines from the ‘Côtes’? . One can imagine conflicts and the regulatory problems that it would create. It is also worth mentioning that the higher you go in altitude, the more the sun is powerful and it is only if the temperature difference between night and day is sufficiently high that it will be beneficial for the plant.

 

WATER AVALABILITY AND IRRIGATION

 

Global warming will undoubtedly bring less precipitation and a reduced availability of water in most viticultural areas. This was well illustrated during the dramatic drought that Australia suffered for a decade (2000-2010). Most of the water comes from the Murray-Darling basins and was seriously limited for agricultural purposes. The drought of last four years in California is also putting great pressure on water availability to the agriculture and to the population. Australia is slowly coming out of industrial viticulture in the Pathaway region, as it is highly demanding in  water supply and irrigation. It is likely that the New World will be more affected, 83% of vines are irrigated in the New World but only 10% in Europe. With 10% of the vines irrigated over 23,000 hectares, the Languedoc is the largest irrigated region in France, Irrigation is strictly regulated in Europe as it increases yields and reduces quality, but the authorities are beginning to understand that without irrigation, viticulture will become increasingly difficult to carry out.  Irrigation is now allowed in Tuscany, but in France it is forbidden between bud break and grapes changing color (Véraison) except by exemption from the INAO.

It is now widely accepted that a certain amount of hydric restriction is beneficial for the vine. However, hydric stress is harmful by reducing quality and yields. Drip-feed irrigation is now the method of choice for supplying the right amount of water to vines and has been further refined with techniques such as ‘partial zone root drying’ which involves irrigating one side of the vine while letting the roots on the other side undergo a period of drought (lasting between 5 and 14 days) following which the irrigation is switched to the other side). This begs the question as to why we make such fuss about irrigation while we can now desalt sea water which is plentiful. But desalting water is highly energy intensive and in a context where reduction of CO2 is mandatory, to limit the climatic change, it is becoming a sensitive issue, especially for viticulture, which is not a priority for a large part of the population. There will be increased competition between human needs in the context of an increasing population and the need of agriculture. The water table is decreasing in most areas of the world and water that comes from glaciers (Andes) is also being reduced, as they are highly susceptible to climatic warming. Interesting research by the INRA indicates that used water could be employed, a viable alternative when sufficiently purified.

 

PICKING EARLIER

 

This is a subject that has been agitating the wine world for some 40 years and often split the opponents into two distinctive camps. On one side, Robert Parker and his alter ego Michel Roland, who have largely imposed their views, not without talent. Maturity of grapes has to be pushed as far as possible to get physiological ripeness. On the other side, a fairly large bunch of despisers, mostly Anglo-French, highly trained and experienced, with equal talent as the other camp, argue that the grapes are over matured and produce wines lacking elegance, refinement and finesse. There is no infallible method to evaluate physiological and phenological ripeness of grapes. The phenolic compounds responsible for color, astringency and bitterness cannot be measured precisely and a link between organoleptic qualities and specific components in the wine is difficult to establish. Alcohol has an essential role in sensorial perception. It tones down the sensation of acidity, enhances the sweet notes of the wine and contributes to the softness and the roundness of  wines. With lower degrees of alcohol, wine is perceived more acidic and more astringent. Europe has a tendency to privilege drinkability of wine whereas the New World seems to be seduced by softness, roundness and sweetness.

It would therefore appear that optimal maturity is more a matter of taste than science.  Maturity has to be judged in relative not absolute terms that can result in an increase or a decrease of  1.5 to 2 o in one way or another without considering that grapes are over or under matured.

 

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VINE PRUNING AND CANOPY MANAGEMENT

 

These two techniques, closely related, will probably be the major way that the climate warming will be dealt with in the vineyards at least initially when the temperatures are contained within a 2 to 2.5o C increase. On this, the New world is much more advanced and has highly competent scientists, such as Richard Smart, who have been working in this field for a long time. In Europe, pruning has been devised largely to expose grapes to the sun as we are in a ‘cool climate’ viticultural area. In the New World, canopy management tends to be conducted to protect grapes from too much exposure to the sun, hence slowing down the ripening process and limiting the alcoholic strength of the wine. When recently touring the vineyards in Australia, I noticed that the alcoholic strength of some wines, including the top cuvées had been lowered by as much as 2o despite the worst droughts and heat waves that struck Australia for a decade. Domains which built their reputation with high Parker points and high alcohol are now turning their backs on these wines which are now considered too heavy and marked by too much wood. There are wines, in the Margaret River in particular, that are perfectly ripe at 12.50 of alcohol.  I am not sure that Bordeaux can do great wines to day below 14o.

But as global warming progresses inexorably over the next century, it is unlikely that the situation will remain static, even in Bordeaux.

 

In warm regions Gobelet pruning has proven its superiority to most other techniques to face extreme heat and is used extensively in the South of France, Spain and South Africa as well as many other warm regions. This tendency towards a protective canopy management will increase in the New World, but in Europe where pruning is regulated and where climatic changes will increasingly constitute of heat wave’s episodes and extreme rain patterns, how do you adjust pruning and canopy management while you do not know what the weather will be like between budding and picking?

 

HUMIDIFICATION AND WATERING OF FOLIAGE

 

It is quite possible to grow grapes and make wine in very hot climates and the Hunter Valley in Australia is the most extreme example. Temperatures in this region can reach 45o C and it often rains heavily as the Valley is oriented east-west allowing rain and winds coming from the ocean to engulf the valley. Extreme heat and rain are not two parameters that you associate very easily with good viticulture and fine wine. Without abundant rain, it would be too warm for photosynthesis to be carried  out and vines would switch off in this region. Without the heat, diseases would soon invade the vineyards. This region can make unique Semillon at about 11.5o and Shiraz at around 13.5 o. It is of course difficult to reproduce this situation artificially, but experiments are taking place in Chile with the utilization of fine water particle sprinklers in order to facilitate photosynthesis. The efficiency of this technique in a context of heat wave’s episodes remains to be demonstrated. The shortage of water is also another limiting factor.

 

MASSALE OR CLONAL SELECTION IN THE CONTEXT OF CLIMATIC CHANGE?

 

Another subject that often divides winegrowers passionately. Clonal selection often preferred over the last 50 years is now losing ground to massale selection, at least conceptually. With massale selection, only vines that show the best resistance and the best adaptation to the vineyard are chosen for propagation. We must not forget that vines have not been subjected to hybridization for a long time and that the destruction of most of the vineyard worldwide with the phylloxera has grossly impoverished its genetic diversity.  Changes in varieties are the result of one single somatic mutation on the genetic sequence of the grape and the majority of grapes worldwide are closely related. One mutation will change a white grape variety into a red or will produce a totally different grape variety with very different organoleptic characteristics. Clonal selection, which introduces a greater control of the quality of the vine in particular for virus contamination but it takes 10-15 years to produce a clone, and only clones required are picked, further reducing the diversity. Massale selection has  the   advantage of picking the best plants and introducing, at least some added resistance even though there is no modification of the genetic sequence. It is a sort of epigenetic equivalent to human genetics. To the greater diversity of massale selection can now be added some confidence about the health safety of the plant as some nursery are now proposing testing  the plant for health and viral contamination. Massale selection seems to have a distinct advantage over clonal selection not only in terms of diversity but also in terms of adequacy to a particular terroir, especially in a context of climatic change.  

 

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WHICH VITICULTURE IS BEST SUITED TO CLIMATIC CHANGE?

 

It is a difficult question to answer scientifically and conclusively, but there is some evidence that synthetic chemistry impoverishes soils. Organic and biodynamic viticulture builds up the resistance of the plants to defend themselves naturally. The French vineyard, which occupies 3.3% of the soil, uses 14,3% of all chemicals in France. With more natural cultures, biodiversity is increased and carbon emission reduced. Cover crop needs to become the norm to stop the warming of the soil. Mulching, the use of humid straw is another method to conserve freshness. Picking at night may become the norm as will stocking the grapes in cold chambers. These methods are already used in some regions.

However, as countries attempt to keep their viticulture under the same latitudes, the displacement of the fauna and flora will take place in line with the change in temperature to look for their natural habitats. In this context, vineyards will be confronted with new challenges. Whether synthetic treatment or biological treatment will have the same efficiency remains to be seen.

 

 

 

DEVELOPEMENT AND USE OF ROOTSTOCKS MORE RESISTANT TO HEAT AND WATER STRESS

 

Rootstocks used today come from the American ancestors of three varieties, Vitis riparia, Vitis berlandieri and Vitis rupestris. The latest, which comes from the south and the west of the USA, has a very extensive root system that can dig deeper into the soil to reach water reserve. This variety, with its current derivatives, is more adapted to dry conditions. Others are more resistant to heat, but it is worth noting that the capacity of rootstocks to cope with hydric stress and heat is always limited by the thickness and the structure of the soil.

 

THE USE OF NETTING AND CHIFFON VOILE

 

This is extensively used in the Margaret River in Occidental Australia to prevent voracious birds eating the crops and  to avoid  disastrous years such as 1971 when birds devoured the entire crop. Its secondary effect, like chiffon voile is to reduce, the light intensity on the vineyard. It is effective, but costly.

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