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agronomy

Water, sun and wine

Brazilian model for classifying climates designates a hundred wine producing regions in 30 countries

Few know the climate and the potential of so many vineyards as engineer-agronomist Jorge Tonietto, from Embrapa Grapes and Wine, in Bento Gonçalves, the capital of Brazilian winemaking, in the northeast of Rio Grande do Sul. Four years ago, when he finished his doctorate in France, this descendent of Italians who migrated to the Rio Grande do Sul hills formulated a complex system for classifying the meteorological conditions that are essential for vines to produce quality grapes for making a good wine. And he dived into a Herculean task: after collecting a mountain of data, in partnership with the World Meteorological Organization (WMO), he compared the climate of a hundred wine producing regions, scattered over 30 countries. He did so, of course, using his methodology, which adopts a combination of three indices to draw conclusions, whilst the majority of other systems uses a single parameter.

Suffice it to look at a graph with a summary of the results of this mega-collation of equations for it to become clear that there are no two areas with exactly the same conditions of temperature and humidity. But there are indeed vineyards with a very similar climate, which can be placed side by side in one and the same group. The work has made it possible to separate the one hundred wine growing zones – a little over half of them located in Europe – into 38 climatic groups. “Never has a study been done of the climate of the wine producing regions on a world-wide scale and with more than one criterion for analysis”, says Tonietto, who was able to rely on the support of his supervisor, the Frenchman Alain Carbonneau, of the Ecole Nationale Supérieure Agronomique de Montpellier (Ensam), the second author of the system.

Some of the results of the work are surprising. Do you know in which part of the globe are the vineyards that enjoy the climate most like the climate of Bordeaux, the region in the southeast of France that is the Mecca of wine lovers? Right there in France, in another three regions: Cognac, Agen and Toulouse. According to Tonietto’s classification, the four regions have a sub-humid climate, with temperate days and cooler nights. Do you like red wines aged in oak barrels with the vanilla flavor of Rioja, the most famous wine-producing region in Spain? In this case, the result was less noteworthy. Characterized by being moderately dry, with the daytime temperatures oscillating between hot and temperate, and fresh nights, the climate of Rioja is almost the same as the climate of Montélimar (Rhône Valley, France) and of Anadia (Bairrada, Portugal).

And the Brazilian vineyards? Bento Gonçalves came out in the same group as P’ohang and Suwon, two zones in South Korea, a country with even less tradition in the world of Bacchus than Brazil. The three areas are defined as humid, with days ranging from hot to temperate, and temperate nights. The other Brazilian region studied revealed itself to be a case of its own. With its tropical wine-growing, in an area that is moderately dry and perennially hot, Petrolina, on the border between the states of Bahia and Pernambuco, in the São Francisco Valley, made up on its own a climatic group with just one member.

What do these comparisons serve for? The climate of the different wine growing regions, located in their majority in temperate or Mediterranean zones, is responsible, in great measure, for the diversity of the strains under cultivation and influences some of the characteristics of wine, such as the quality, the style (whether it will, for example, be white, red, sparkling, fortified, or more or less full bodied) and the typicality (the set of predicates associated with the region in which it was produced). “That is why we need to be perfecting all the time the forms of comprehension of the meteorological factors, if we want to carry out a proper zoning of the areas of production”, says Tonietto. Logically, besides the atmospheric variables, other factors dictate the characteristics of a vineyard and of a wine, such as the composition of the soil in which the vines grow, the variety of grape planted and the competence and tradition of the wine grower. But the climate is the main factor of limitation forthe expansion of the cultivation of Vitis vinifera, the ideal species of grape for making wine.

At least 7,000 years planting vines and making wine has taught man some lessons on the climate. Generally speaking, hot areas are more propitious for producing full bodied, dense wines, with a high content of alcohol. Potent and fortified wines in the style of Port wine are usually born in vineyards where there is no lack of sun in the period when the grape is coming to maturity. The vocation of cold regions lies with light red wines and aromatic white wines, or with sparkling wines. Between these two extremes, there is an infinity of intermediate climates, often difficult to be perceived or even differentiated, which may favor the production of the most varied styles of drink.

Since the first half of the last century, climatic classification models have been a useful instrument for finding more quickly the vocation, or the vocations, of the productive zones, without depending just on the empiricism of the wine growers, the old method of trial and error. To arrive at the new methodology, baptized as Multicriterion Geoviticultural Climatic Classification System (CCM), Tonietto did not need to reinvent the wheel. His merit was to trim a few rough edges of two equations known to the world of wine growing, formulated by French researchers and normally used in isolation, the Charles Riou index of dryness and the Pierre Huglin’s heliothermic index. He added a third index to these two formulas, for night l coldness, which he himself created. Voilà: the Geoviticultural CCM was ready.

The first index, of dryness, draws up a balance of the quantity of water available for the vine during the stages of the plant’s growth and coming to maturity, the period that comprises the six months that precede the annual harvest. In the vineyards of the Southern Hemisphere, this stage generally runs from October to March. In the grape trellises to the north of the equator, it starts in April and extends until September. The second index, the heliothermic index, quantifies the effects of the heat and of the sun on the vine in the same six months used for calculations with the previous formula.

Finally, the third equation gives an idea of the degree of coolness of the nights in the course of the last monthof the vines coming to maturity (in general, March in the Southern Hemisphere and September in the North). In figures, nocturnal cold is just the average of the minimum temperatures recorded in the month of the harvest. As the minimum occurs after the sun has set, the index was given the name of nocturnal cold. “Introducing this last parameter into the system has improved the assessment of the qualitative potential of the wine growing regions”, Tonietto explains. Indeed, the occurrence of mild nights at the end of the vine’s process of maturing, in mid-summer, brings the wine more color and a richness of aromas.

The system devised by Embrapa’s researcher passed the first test while still on French soil, where wine growing is an affair of State. Before being used in the international mega-project of the hundred regions, the Geoviticultural CCM was used to analyze the climate of 18 wine-producing areas from the south of France, which used to grow the Syrah variety of grape, well suited to hotter regions. The results encouraged everyone. The methodology managed to give a precise outline of the climate of these regions and – an important detail – succeeded in establishing relationships between the meteorological conditions of the vineyards and the basic characteristics of the wines cultivated in these parts of the land. “CCM is currently the best methodology for characterizing the climate of a large region, like the hills of the state of Rio Grande do Sul, or of small areas, like a foothill in the environs of inn the city of Bento Gonçalves, also in Rio Grande do Sul”, was the opinion expressed, without any falsemodesty, by Alain Carbonneau, from Ensam. “The integration of three indices has become the basis for defining zoning wine-growing regions.”

This system of climatic classification is already very valuable for the development of wine growing, above all in tropical regions. In these low latitude areas, stimulated by the heat throughout the whole year, the vine speeds up its cycle of development and goes so far as to give more than one crop every 12 months. Petrolina, in the state of Pernambuco, for example, has five harvests in each two-year period. For the more orthodox, this crazy cycle of the vines in hot terrain is an obstacle to the formation of quality vineyards and synonymous with bad wine. Now comes the novelty discovered by the Geoviticultural CCM: from the point of view of the vineyard, Petrolina does not show just one climate throughout the year, as the majority of wine producing regions do, but three. And what is more interesting is that the wine growers can derive benefit from this and thereby achieve a better quality product.

This calls for an explanation. At this spot in the São Francisco Valley, the first type of climate occurs from January to March, when it is hot by day and by night, but it does rain a bit. In this period, harvesting the grapes is not recommendable, since rain at harvest time leads to diluted, watery wines. The second climate, hot by day and by night and without any rain, is good for harvesting; it covers the months of April, May, October, November and December.

Finally, Petrolina’s third climate is regarded as the best for wine growing. From July to September, it is hot by day, it rains little, and – something rare in the northeast – there is a bit of a chill at night, which is good for setting the color and for developing aromas in the wine. “For us to harvest always at a suitable time of year, we are going to control the growth cycle in our vineyards in Petrolina and prevent the worst crop from occurring, which is the one that coincides with summer”, explains Adriano Miolo, an enologist from one of the best Brazilian firms producing wine, Vinícola Miolo, from Rio Grande do Sul.

His idea is, in one year, to carry out two harvests (one in July and the other in December) and, in the following year, to have just a single harvest, in September. “Jorge Tonietto’s work has overturned the taboo that wine growing is only viable in the more temperate climates, between the 30th and 50th parallels in the Northern Hemisphere and between the 20th and 40th in the South Hemisphere”, explains Miolo. Petrolina, by the way, is on the 9th parallel.

A seal for the Vale dos Vinhedos (Vineyard Valley)

In the land of cachaça and coffee, it is wine from the heart of the hills of the state of state of Rio Grande do Sul (Serra Gaúcha) that has won the honor of being the first Brazilian product to receive from the National Institute of Industrial Property (Inpi) the right to flaunt a symbol that attests to its geographical origin. This recognition is the first legal step towards building up an identity that characterizes the products from a region. On November 22 last, after a process that extended for eight years and was able to rely on technical advice from Embrapa Grapes and Wine and from the University of Caxias do Sul, the Association of Producers of Fine Wines from Vale dos Vinhedos (Aprovale), which gathers together 24 wine making companies, has been given the green light, on a definitive basis, to wrap a seal round the neck of their bottles. The seal reads: Attests to Vale dos Vinhedos Origin.

This means that the wine packaged in bottles with this distinction is fermented from varieties of grapes of the Vitis vinifera species planted in a delimited and controlled area: Vale dos Vinhedos, with its 81.23 kilometers, which stretches over Bento Gonçalves, Garibaldi and Monte Belo do Sul. To be awarded this distinction, Aprovale’s producers entered into a partnership with research institutions in Rio Grande do Sul in the quest for a central objective: characterizing in the greatest of detail the geography of the valley, the region of the Serra Gaúcha with most tradition in the production of fine wines in Brazil, whose topography, soil and climate have been studied in their smallest particulars.

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