By Zukhanye Fondile, Tracey-Lee Johannes, Relebohile Mabaleka, Zinhle Msiza, Imi Mxabo, Ziphozinhle Nkosi, Neo Segopolo, Ezile Zitha & Anton Nel
In the second part of the Terroir series, we continue to examine the influence climate has on terroir. We will also examine the role of cultivars in terroir. Finally, we will conclude with something new and not yet defined by terroir: the influence of different microorganisms on the taste and quality of wine and how they fit into the terroir concept.
How climate change is shaping the future of winemaking
Climate change is no longer just an abstract issue, but a reality that’s reshaping industries across the globe – especially the world of winemaking. As renowned wine scientist John Gladstones (2011) explores in his book Wine, Terroir and Climate Change, rising temperatures, shifting precipitation patterns and extreme weather events are already having profound effects on vineyards. Here’s how climate change is rewriting the rules for the wine industry.
Climate and grape development
The climate is another significant factor affecting grape quality, and it operates on three levels: macroclimate (regional), mesoclimate (site-specific) and microclimate (vine canopy level). Of these, microclimate has the most direct influence on grape development. Different grape varieties thrive in varying climates, and changes in temperature during the growing season can accelerate or slow down the ripening process. Cooler conditions tend to favour more gradual sugar, acid and flavour development, leading to more complex and aromatic wines (Van Leeuwen & Seguin, 2006).
In warm climates, grapes ripen more quickly, resulting in higher sugar levels, but lower acidity, which can unbalance the wine’s overall flavour. Grapes should ripen during the cooler end of the growing season to fully express the terroir’s unique qualities (Van Leeuwen et al., 2007).
Rising temperatures and their impact on grapes
As global temperatures continue to climb, the effect on grape ripening is unmistakable. With warmer temperatures, grapes mature faster, leading to earlier harvests. While this might sound like a good thing, it can drastically alter the balance of sugars, acids and tannins in the fruit. Warmer climates may increase the sugar content, boosting alcohol levels in wine, but potentially reducing the complexity of its flavours, particularly in cooler regions like Burgundy or parts of Germany. The nuanced flavour profiles that define some of the world’s most famous wines could be at risk (Gladstones, 2011).
Water woes – droughts and excess rainfall
Changes in precipitation patterns present another challenge. In key wine-growing regions like Southern Europe, California, South Africa and Australia, prolonged droughts are becoming more frequent. This means that vineyards might have to rely more heavily on irrigation. However, in areas where water resources are already scarce, disputes over water rights could become more common, and winemakers may be forced to adopt water-saving practices like dry farming or alter their vine training techniques to conserve moisture.
Conversely, some regions may experience excess rainfall, especially during the critical harvest period. Too much rain increases the risk of diseases like mildew and rot, potentially devastating vineyards. Additionally, it can dilute the grapes, weaken flavours and reduce the quality of the final product (Gladstones, 2011).
Extreme weather – frost, hail and heatwaves
More extreme weather events, from hailstorms to frost and heatwaves, add to winemaking’s unpredictability. Late frosts in spring can destroy delicate buds and emerging shoots, while hailstorms can wipe out entire vineyards in minutes.
Heatwaves present another severe threat. Vines exposed to excessive heat may experience stress, leading to early ripening and fruit shrivelling. This has led many winemakers to adjust their vineyard practices, using techniques like canopy management to provide more shade or moving vineyards to more excellent areas at higher altitudes to mitigate heat risks (Gladstones, 2011).
Adaptation strategies in the face of climate change
The wine industry is developing several strategies to cope with these climate-induced challenges. One approach is shifting grape varieties. For instance, warmer regions might begin planting more heat-resistant varieties like Grenache, Mourvèdre, or Syrah, which can thrive in higher temperatures while still producing high-quality wines.
Vineyard management practices are also evolving. Growers can reduce the impact of rising temperatures by changing planting density, adjusting the direction of vineyard rows and altering pruning methods. Technological innovations, such as smart irrigation systems and climate forecasting tools, are helping winemakers adapt to changing conditions (Gladstones, 2011).
Long-term sustainability – a call to action
Looking ahead, Gladstones (2011) calls for the wine industry to embrace long-term planning and sustainability. He advocates for adopting organic, biodynamic and regenerative agriculture practices, which could mitigate environmental impact and enhance economic stability in the face of a changing climate. Collaboration and information sharing within the industry are also vital in ensuring winemakers stay ahead of climate risks. By working together, the industry can develop innovative solutions and policies to protect the vineyards and the winemaking legacy (Gladstones, 2011).
Cultivar and nutrient dynamics in a changing climate
Beyond climate, the soil – rich in nutrients and microorganisms – plays an equally vital role in shaping wine quality. Healthy soils provide essential macronutrients like nitrogen, phosphorus and potassium, which are crucial for vine growth. A study by Maathuis (2009) highlights the importance of these nutrients in supporting photosynthesis and fruit development.
However, micronutrients like zinc, copper and iron are equally essential, although required in smaller amounts. Sharma et al. (2024) say these micronutrients boost plant productivity and resilience. Research by Gobbi et al. (2023) further emphasises the importance of microbial communities in soil, showing how microorganisms like Rhizobia and Bacillus contribute to nutrient cycling, influencing grapevine health and wine quality. These microbes help fix atmospheric nitrogen and make phosphorus more accessible to the vines, highlighting the intricate connection between soil biology and terroir (Gobbi et al., 2023).
Understanding the impact of terroir on wine quality – a look at soil, climate and microbial influence
The concept of “terroir” in winemaking goes beyond just geography. Terroir encompasses a range of environmental factors – including climate, soil, topography and even microbial life – that influence the growth of grapevines and ultimately determine the quality of the wine produced. According to Seguin (1986, 1988), these elements combine to form a unique ecosystem that shapes the characteristics of grapes and, by extension, the wine made from them.
The microbial influence on terroir
Recent research has highlighted the role of microorganisms – such as bacteria, yeasts and fungi – in contributing to the unique character of a vineyard’s terroir. These microbes affect everything from nutrient availability in the soil to the fermentation process that turns grape juice into wine (Gilbert et al., 2014). In fact, different regions have distinct microbial communities that can influence wine flavour and aroma, adding another layer of complexity to terroir (Knight et al., 2015).
Microbes like Proteobacteria and Acidobacteria dominate vineyard soils, while fungi such as Cryptococcus are also prevalent (Gobbi et al., 2022). These organisms play vital roles in nutrient cycling and help vines absorb essential minerals. By fostering healthy microbial communities, winemakers can enhance grape development and, ultimately, wine quality. In some cases, beneficial microbes can even protect vines from pests and diseases, offering a natural form of pest control (Nerva et al., 2021).
During fermentation, specific microbes – particularly yeasts like Saccharomyces cerevisiae – are essential for converting grape sugars into alcohol. This process also produces secondary metabolites that significantly influence wine flavour and aroma. While some researchers argue that microbes have little direct influence on grape chemistry, their role in fermentation is undeniable (Gilbert et al., 2014).
Microbes have been identified as an important component of the ultimate sensorial properties of wines through fermentation. The impact of microbes on wine fermentation, especially lactic acid bacteria and yeasts, has led to the creation of commercial products which can be used during alcoholic fermentation (Gilbert et al., 2014:5).
All ecological interactions that take place between the microbiota, the plant and the environment play an important role in the outcome of wine fermentation (García-Izquierdo et al., 2024). Fungi can profoundly influence the phenotype of wine by impacting the health and development of grapevines and berries, thereby affecting quality. Additionally, they control wine flavour, aroma and style through their roles in the fermentation process. During this process, Saccharomyces cerevisiae – the main yeast used for alcohol fermentation – converts sugars into ethanol and generates a range of secondary metabolites, including volatile compounds, that significantly influence the wine flavour and aroma (Knight et al., 2015:2).
Integrating microbial ecology into agriculture could revolutionise site selection and management by using probiotics to introduce beneficial bacteria that improve soil quality and increase crop yields (Gilbert et al., 2014). Additionally, this method can improve wine terroir or even reproduce those favourable terroirs in areas unsuitable for producing wine with such properties (Gilbert et al., 2014). Microbes are complex species, according to Knight et al. (2015), and are often unpredictable, which makes their chemical and sensorial properties difficult to control experimentally. Gilbert et al. (2014) argue that bacteria and fungi only play a role in the fermentation process and have little direct influence on grape chemistry. Alexandre (2020:1) also argues that while the microbial community of a vineyard is dependent on geographic location, there is no strong evidence that microbes contribute to the so-called “terroir effect”.
The microbial terroir of wine grapes plays a crucial role in winemaking, affecting both vine health and the quality of the wine produced. By gaining a better understanding and managing the microbial communities in their vineyards, viticulturists and winemakers can improve vine health and shape the distinctive qualities of their wines. However, more thorough research needs to be done as the concept of microbial terroir is still the subject of intense debate (Alexandre, 2020).
The future of terroir and microbial management
The emerging understanding of microbial terroir opens new possibilities for viticulture. By managing and even introducing beneficial microorganisms into vineyard soils, winemakers may be able to enhance the expression of terroir and produce wines with distinct, desirable characteristics (Gilbert et al., 2014). While some debate continues regarding the extent of microbial influence, particularly regarding grape chemistry (Alexandre, 2020), it is clear that microbes are an essential factor in the complex interactions that define terroir.
Conclusion – terroir as a dynamic concept
Though often tied to tradition, terroir is not static. It evolves with new knowledge, techniques and even climate change. As winemakers experiment with different approaches, terroir will continue to be a focal point in the ever-changing world of wine. Whether you’re sipping a bold red from Bordeaux or a crisp white from the Loire Valley, you’re tasting not just the grape, but the unique blend of earth, weather and human expertise that makes each bottle of wine truly one of a kind.
In the world of wine, terroir is everything, and soil is one of its most crucial components. From regulating vine temperature to providing essential nutrients, soil plays a key role in shaping the character of the wine. As research continues to shed light on the impact of soil on grape quality, it becomes clear that this hidden factor holds the key to understanding the complexities of terroir. Whether you’re enjoying a bold red from Valpolicella or a crisp Albariño from Spain, remember that it’s the soil beneath the vines that helps make each bottle truly unique.
In conclusion, terroir is a multifaceted concept that encompasses soil, climate and microbial life, all of which influence grape quality and wine production. By understanding and managing these factors, winemakers can harness the unique characteristics of their vineyards to produce wines that truly reflect their place of origin. As research into microbial communities continues to evolve, it may revolutionise how we think about terroir and winemaking, leading to even greater innovations in wine production.
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For more information, contact Anton Nel at nelap@cput.co.za.
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