These changes are already occurring at a global level: warming due to a rise in sea surface temperature, an increase in minimum and average temperatures, a greater frequency of extreme events, changes in water regimes, etc., already have their effects on crops. They are clearer in the northern hemisphere, particularly with greater impact in the countries of the old wine world.
In South America and, particularly, in Argentina, it has been only a few years since this topic has begun to stir scientific interest, since there are still many uncertainties regarding the future of the region in terms of climate, with only one serious source of analysis, such as the reports of the IPCC (Intergovernmental Panel of Experts on Climate Change).
Some consequences of these changes can already be observed:
expansion of the viticultural frontier towards Patagonia,
changes in the course of phenologicalcicle
alteration in the relationship among sugar, acids and other compounds of the grapes
We should pay special attention to extreme events to avoid major losses in crop yields (heat waves, frost and hail frequency, etc.).
The great dilemma is: how to achieve quality and sustain it in time in conditions of high climatic variability?
SOME INDICATORS OF THE VARIATIONS DUE TO THE CLIMATE EFFECT
Average Annual Temperature Increase in the Uco Valley.
Increase in the Winkler index estimated for the Uco Valley.
Simulations of the isotherms for 12 and 22 degrees, limits of vine cultivation.
Evolution of the average alcoholic concentration estimated for the Uco Valley.
Evolution of the final pH in the wines of the Uco Valley.
CLIMATE FACTORS AND HOW THEY ACT ON CROPS
Regarding temperature, the vine is a plant sensitive to frost and demands some heat to carry out its development and the correct ripening of the berries. The average temperatures for a correct development of the crop must be higher than 9º C, the optimum being between 11º C and 18º C, with the ability to tolerate temperatures up to -1.5º C and 40º C during the vegetative period. During the winter period, they can resist temperatures as low as -12º C in the buds and -20º C in the wood. The olive tree is even more sensitive to cold in winter and spring, tolerating just a few degrees below zero. During the summer, the temperature requirements are remarkably similar to that of the vine and that is why historically these crops have been associated.
Temperature and light are vital for the concentration of sugars, acids, aroma precursor molecules and polyphenolic substances in the berries during the ripening period, determining the style of wine and its quality. Regarding olive oil, temperature also determines the degree of phenols (which is substantially higher in oil than in wine) and determines the aromatic and acid levels that indicate quality.
Both crops are adapted to some lack of atmospheric humidity, with a minimum water requirement of 400 mm of annual rainfall for their proper development. The maximum water need corresponds to the growth period between flowering and veraison, in which the fruit develops.
The vine solves the lack of rain with a powerful root system that allows it to take advantage of the moisture stored during the rainy periods in the deep layers of the soil, while the olive tree combines this technique together with the reduction of the size of its leaves and the secretion of rubbers to minimize respiration; by doing this, plants manage to maintain photosynthesis and sap transportation for a correct ripening. On the other hand, an intense rainfall regime in spring-summer is not favorable since it favors the appearance of diseases caused by fungi.
Vine and Olive require light exposure, around 1500 to 1600 hours per year in average.From that amount, a minimum of 1200 hours correspond to the vegetation period. Canopy density management factors (vegetable expression) play an important role in defining the percentage of differentiated buds (productivity) due to the light intensity that arrives to them. Direct lighting on buds promotes floral induction and differentiation and hence a satisfactory fertility index. For this reason, shading is the most decisive factor in reducing yields and grape quality. The same happens with the lack of light: it is detrimental to plants, an excess can also affect them.
This significant influence exercised by the climate on the crop is reflected in the distribution of the areas of production in the world. The development of viticulture has traditionally taken place in non-extreme Mediterranean-type climates. Nowadays the borders of the warm zones have disappeared due to the appearance of tropical viticulture. This is a consequence of having overcomeits difficulties by the application of the appropriate technology. Towards the extreme north and south of the planet, the limitations are a consequence of low winter temperatures in continental areas, which prevents plants development and survival, with frequent and strong frosts ( -15º C). There are more possibilities for a proper ripening of the grapes in areas with a clear Atlantic influence, less thermally extreme.The challenge then is temperature and light necessary for the correct ripening of the fruit.
ACTIONS THAT TEND TO MINIMIZE THE EFFECTS
There are various technical tools that make it possible to deal with these phenomena, either actively or passively. In established vineyards and olive groves, actions to be taken are limited compared to new plantations, where the place, the layout and the variety to be implanted can be thought from scratch.
IN VINEYARDS ALREADY PLANTED:
The practices that can be applied in established vineyards aim at the following objectives:
• Minimize the loss of water from the soil and the crop
• Maximize varietal expression
• Avoid climatic contingencies of any kind (frost, heat waves, hail, El Niño phenomenon, etc.)
Under this premise, for the climate of Mendoza, conserving the water resource becomes fundamental. That is why the use of drip irrigation, the waterproofing of ditches and dams, the construction of dams and the constant study of the atmospheric demand for water and water retention capacity of the soil become essential tools to manage production. Additionally, the canopy management of the crop, the orientation of the rows, the use of forest curtains, the use of rainwater and others passive actions help improvingthe efficiency of water use.
Regarding the expression of each variety: it is essential to understand the climate of the region where production is happening in order to use the most suitable varieties and selections for each area. The combination of different orientations and exposures, the differential management of soil and irrigation as well as the adaptation of field labor for each micro-terroir allows to differentiate management units that have a unique identity and help to achieve complexity, taking advantage of the natural variation of the soil under a particular agricultural criteria that protect the quality of the grape.
Currently, vineyards are protected with anti-hail netting in most projects in Mendoza. This generates two benefits, on the one hand, it directly protects the crop from the impact of hail, which can affect the production of several years if it hits an unprotected plot. On the other hand, it indirectly reduces the intensity of the light that impactsthe crop and helps reducing transpiration. Along with this technological solution, the establishment and maintenance of good forest curtains, and the work of the soil with vegetal cover help to minimize the impact of winds and heavy rainfall that can erode the soils.
The diversification of training systems plays a fundamental role in reducing agricultural risk. This implies knowing well the growth habit of each variety and adapting them to a form of cultivation that maximizes the oenological quality effect. Currently we see a growth of vineyards cultivated in free canopy management systems, such as single wire, gobelets and sprawls.
IN FUTURE VINEYARDS (TO DEVELOP)
In this case, to the already mentioned tools, we can add the topographic tools, the use of natural vegetation as protection, simulations of air and water runoff, exposure in relation to the sun movement, and design of plots according to soil and agricultural variables. All these indexes help to achieve a deep understanding of the place and aim for a smart design, using soil sectors with specific properties for each variety.
It is also important to consider the particular requirement that each variety has regarding humidity, temperature, light exposure and crop management, creating a complex system that allows the design of an agro-ecosystem that favors the establishment of a particular crop.
OENOLOGICAL ADAPTATION MEASURES
Winemaking adaptation measures can be considered as an additional strategy to the agricultural ones to protect against climate change and should focus on specific threats, aiming to optimize production. These measures involve changes in oenological practices, through the use of better adapted microorganisms or the application of new technologies that can have positive effects on the quality of the wine, modifying aromatic expression, residual sugar,color, alcohol, acidity, pH and phenols in wine.
Within the range of techniques to control evolution and wine-making factors, one of the main consequences of climate change on viticulture are wines with a higher pH level. This generates a decrease in microbial stability, forcing to strengthen the doses of sulfur, which in turn loses its effectiveness with the increase in pH. In this sense, there are options for the replacement of sulfur and resorting to specific doses of products based on yeast and bacterial microflora and the restriction of available oxygen.
Up to now, acidity correction was carried out almost exclusively by adding organic acids, mainly tartaric acid. However, with such high pH levels, the permitted doses no longer manage to ensure the structure and stability of the wine in all circumstances. For this reason, the differentiation of harvest times becomes critical, selecting fresh expressions of the plots that act as a guard for malic acid and allow a more naturally balanced blending.
FINAL THOUGHTS
Climate change is a reality and predictions say that if Greenhouse Gas (GHG) emissions continue at the same rate, the increase in temperatures and the decrease of precipitations will continue. However, due to the different topographies of the terrain, these climate changes will not occur in a homogeneous way. Given the high dependence that viticulture has on the climate, it is necessary to assess the consequences of climate change, both in quality and in the productive potential of the vineyard. The increase in temperatures would lengthen the vegetative period of the vine and all its phenological stages would be accelerated, including ripening. This fact would have positive consequences in cold areas, since ripening would become complete, but in warm areas the consequences would be negative, since they would cause imbalances in the composition of the grape due to excessive ripening, risking the quality of the grapes.
Traditional wine-growing areas can be threatened not only by the economic cost that must be assumed to implement the different adaptation strategies, but also by the appearance of new production areas, since this change in climate makes it possible to grow crops in those areas where a few years ago it was not a possibility, due to weather conditions.
The incorporation of technology and the constant study of growing conditions together with the development of new selections adapted to hot climates are essential to ensure a future that allows us to continue the path of quality and sustainability.
Luis Coita Civit
Agricultural Specialist
Precision Agriculture Expert
Agricultural Engineer, specialized in water
management and precision agriculture.
He worked in Argentine for companies such as
GrupoPeñaflor, Chandon and Cheval de Andes.
He also studied and worked in France and
New Zealand. He is currently an agricultural
consultant and business developer.