Wine

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Factors which threaten the production of wine

Physical factors

Terroir describes the environmental factors of an indigenous geographical location. It delineates the different environmental factors of a locale that contribute to the flavour and character of a product. It originated in the wine-making industry. The terroir for wine involves temperature, humidity, precipitation, wind/airflow, minerality of water, altitude, aspect, slope, light exposure, and soil composition. There is no one terroir that suits every situation and every type of grape in every vineyard. But in general, we have an idea of the ideal climate aspects of terroir.

Wine growers everywhere would be ecstatic with adequate precipitation and warmth to grow the vine and ripen the fruit, with no weather extremes (like frost, hail and heat waves) and disease. During the dormant period, this would equate to enough soil-replenishing rainfall and a cool to cold winter, without vine-killing low temperatures but with enough chilling to ensure bud fruitfulness the following year. The spring would be free from wide temperature swings and frost, and have enough precipitation to feed vegetative growth. During flowering, the weather would be cloud-free with moderately high temperatures and high photosynthetic potential to allow the flowers to fully set into fruit. The summer growth stage would be dry, with heat accumulation to meet the needs of the variety and few heat stress events. The ripening period would be dry with a slow truncation of the season toward fall, with moderately high daytime temperatures and progressively cooler nights.²

According to current climate research, global warming will increase occurrences of extreme weather and change the predictability of seasonal patterns we have come to rely on.

Temperature is probably the most studied physical factor affecting the growth and development of grapes.

Without cultivar turnover, our results predict major global gains and losses in future winegrowing regions. Under a 2 °C warming scenario, 51% of all areas we identified as climatically suitable for winegrowing under our 0 °C reference scenario would be lost. At 4 °C, losses reach 77%.³

Precipitation is another consideration. In some parts of the world (e.g. California in the USA, almost everywhere in Australia) grape growing would not be possible without irrigation. In other  areas, irrigation was frowned upon/illegal as there were strict legal guidelines as to how grapes were allowed to be managed to keep their accreditation credentials intact. In France, where irrigation was formerly banned, climate change has influenced the INAO, the Institut nationale de l’origine et de la qualité (formerly called Institut nationale des appellations d’origine), to decide that water systems can be used in certain circumstances due to developing scarcity of rainfall and unreliability of seasonal patterns.⁴

Localized case studies are a good way to explore some of the potential change.

Case study - Burgundy (France)

The Bourgogne (Burgundy) region in central France is world renowned as a wine growing district producing some of the most esteemed and expensive wines in the world. It is particularly known for its pinot noir and chardonnay grapes.

Wine has been made in the region for centuries and there are 700 years of records of annual harvest times. Hence, it has been possible to ascertain that the historical harvest period has been moved up two weeks due to warming temperatures.

In March 2021, the month of March was anomalously warm, breaking many high temperature records. This accelerated the start of the growing season for grapevines. This was followed in April by record breaking  frosts, which severely damaged the tender young growth on the vines. The region lost approximately 50% of its multimillion dollar harvest. According to researchers associated with World Weather Attribution

We found that although climate change made the temperatures of the observed event less cold than they would have been without the burning of fossil fuels over the last centuries, the fact that climate change has also led to an earlier start of the growing season means that frost damage in young leaves has become more likely due to human-induced climate change. ⁵

Update: Production will vary between grape varieties and regions but is likely to fall by between 24% and 30% overall versus last year, said Agreste, the statistics arm of France’s agriculture ministry.⁶ And a fire has been burning out extensive areas in the southwest of France.⁷

Case study - Victoria (Australia)

Wine is big business in Australia. There are over 2000 wine businesses in Australia, producing over 1 billion litres of wine annually. Two-thirds of wine sales are exports. Victoria is the southernmost mainland state of Australia.  It is the smallest mainland state and the most densely populated. The state encompasses a range of climates and geographical features - temperate grasslands and woodlands in coastal and central regions, alpine areas in the north-east and  large areas of semi desert in the north-west.

Grapes are grown across numerous regions of the state as can be seen in the diagram on the left. Irrigation is commonly used in grape growing in Victoria, particularly in the regions in the north-west of the state as they are situated close to the Murray river - the largest river in Australia. Surrounding areas both to the north and south are semi desert.

The Victorian State Government released a Climate Science Report in 2019. The 48 page report can be accessed at https://www.climatechange.vic.gov.au/__data/assets/pdf_file/0029/442964/Victorias-Climate-Science-Report-2019.pdf

The main findings of that report are summarised in the diagram labelled Victoria's climate change projections.

 

Wine Australia (a government backed body) has produced regional snapshots of historical climate conditions in the designated growing areas. Temperatures are up and rainfall is going down across the board which will will have a marked influence on grape growing.

Wine Australia has also published Australia’s Wine Future: A Climate Atlas which indicates past and future climatic conditions and their influence on winegrape growing.

Pollinator problems

Not a major threat as grapes are self fertile and do not rely on pollinating agents.

Pests and diseases

Partial list of organisms which attack Vitis vinifera

Organism	Grouping	Comments
Aphid	Insect	Suck sap from leaves. Also maybe vectors of microbial diseases.
Mealybug	Insect	Damage grapes by contamination with cottony egg sacs, larvae, adults, and honeydew supporting sooty mold. Also virus vector.
Root rot nematodes	Nematode	The worms feed on roots, disrupting uptake of nutrients and water, thus interfering with plant growth.
Twospotted spider mite	Arachnid	The leaves wilt, then fall off and fruits fail to thrive.
Grapevine bud mites	Arachnid	Leaves show bumps on top side, blemishes underneath. May prevent flowering.
Downy mildew	Fungus	Leaf lesions are yellowish and oily or angular, yellow to reddish and brown and limited by the veins. Infected young grapes appear grayish when infected and become covered with a downy felt of spores.
Powdery mildew	Fungus	Yellowish spots on the upper leaf surface. Then white, webby mycelium on the lower leaf surface.
Botrytis	Fungus	Patches of soft brown tissue develop resulting in the death of the infected plant part. Gray, velvety appearance of infected fruit.
Anthracnose	Fungus	Leaves become spotty then torn. The fruits become dry and wrinkled during a dry period and during a wet period, they rot.
Crown gall	Bacterial	Causes galls to grow on the trunk and branches
Grapevine fanleaf virus:	Virus	The leaves are under-developed, deformed in that they resemble a fan.
Crows, sparrows, starlings	Birds	Partial or full consumption of fruit crop
Rabbits, rats, possums	Mammals	Partial or full consumption of fruit crop

Climate change can alter the balance between plants and those organisms that prey on them. e.g.

• Increased humidity due to unseasonal rain increases the chances of fungal diseases taking hold.
• Damage to trunks due to frost can increase the incidence of crown gall disease.

 

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What can we do about it?

Since the 1950s, agricultural systems have experienced gradual systematic changes in average climate conditions including unprecedented multi-decadal warming, increased inter-annual variability of the Earth's surface temperatures, changes in average precipitation, greater weather variability, and more extreme weather conditions.⁸

Solutions involve scientific, technical, social, legal and economic factors to varying degrees.

Quantity vs quality

Not only do we have problems about the amount of wine that can be produced, we also need to consider the quality of wines available. There are strong traditional ties to various varieties and brands, built up over generations. But the harsh reality is that consumers and makers may not be able to continue their time honoured practices in the face of a changing, potentially damaging environment. Business as usual will just not cut it.

Mitigation and resilience responses

One example of innovation in the wine industry.

In France, a modified canopy management practice is being trialled. Photovoltaic panels have been installed in a vineyard over growing vines.  Controller units can change the orientation of the panels using Artificial Intelligence programming to control the amount of shading of the vines by the panels in accordance with the prevailing weather. In the event of climatic extremes – droughts, heatwaves, hail, heavy rain, severe frost,  etc – the AI ​​controls the panels which in turn protect the vines.⁹

Another approach, adopted from farming techniques used with other plants is intercropping. This involves planting another carefully selected species mixed in with the grape vines. A recent experiment in 2023 in New Zealand intercropped vines with hemp plants. In this trial, the hemp plants were found to not compete with the grape plants for water, improved soil carbon storage and seemed to impart the grapes with a better flavour. As a bonus, it provided growers with a second income stream.¹⁰

Other responses to the threat to wine include

• Increased irrigation efficiency (where permitted)
• Modified irrigation practices in response to heatwaves and frosts (where permitted)
• Vineyard management practices aimed at retaining soil moisture
• Use of alternative varieties and/or rootstocks
• Establishment of vineyards in cooler regions and/or sourcing cooler climate fruit
• Delayed pruning practices to manipulate harvest dates.
• Use of new technologies in the wine growing/making industry

Pest management can be improved by changing from carpet bombing style eradication to more sophisticated techniques such as
- selective pesticides and timings of spraying to minimise the impacts of pesticide harm to soil biota¹¹
- better management techniques such fine tuning picking times, more sophisticated monitoring techniques
- biological control which involves deliberate release of pests/diseases specific to the pest of the grape vines¹², ¹³

As grape plants are commonly propagated by using cuttings, all plants in a given planting may be clones ie genetically identical and chosen for resistant to a a certain pest or tolerant of a certain sub-optimal physical condition. This can be a disaster though if conditions change and this genotype does not suit the plants to the new prevailing conditions.  It is possible to introduce diversity into plantations by using conventional breeding techniques to produce variability into the genetics of the crop plants. In this case, seedlings are used rather than vegetative clones.

One approach that is being pursued vigorously is bioengineering of the V. vinifera genotype. While faster than conventional crossbreeding programs, this could result in patents being registered on new genotypes generated in labs with all the issues associated with ownership, costs and management. These issues are often underestimated in the rush to find a technofix.  See¹⁴,¹⁵ This is often detrimental to small scale growers, and can result in bitter long-term legal turmoil.

All this change depends on research, education, plus stakeholder involvement in grower, industry and consumer groups.

The economic, environmental and social aspects of sustainable wine production are inextricably intertwined. Wine associations and government at all levels must do more to support the needs of all producers and be mindful of innovations leading to changes in consumption patterns if the industry is to become sustainable in the long-term.¹⁶

And there are those of us who see global climate warming as requiring high level government environment intervention to rescue the whole earth.

• Consider who you vote into power in your country
• Consider your own consumption patterns and who you buy from
• Consider the future and what you want it to look like

 

Acknowledgement of issues not covered on this page

The social effects of change for small farm-holders, the politics of the producer countries, exploitation of manual workers, biodiversity loss due to land use

Information starting points for more information about societal aspects of wine.

• Moral Fibres: A Beginners Guide to Ethical Wine

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Bonus: The journey from plant to commodity

Please note there are many variations in the actual process. Only major steps are included.

Stage	Description
Harvesting Harvesting can be done mechanically or by hand. Hand harvesting, where feasible, is preferable as mechanical harvesters can often be too rough and cause damage to the crop. Once the grapes arrive at the winery, the grape bunches are picked over to remove rotten or under-ripe fruit, stowaway insects and detritus such as leaves before going to into the crushing machine.
Crushing and pressing Grapes are crushed by large machines with a rotating augur like moving part to tear them up, then mechanically de-stemmed and then transferred to a wine press to squeeze the juice out. For centuries, this was done by stomping the grapes, then by manually powered presses. To make white wine, it is necessary to separate the juice from the skins, seeds, and solids promptly.. This is done to prevent tannins and unwanted colour (which comes from the skin of the grape, not the juice) from leaching into the white wine. Red wine is left in contact with its skins to absorb colour, flavour, and additional tannins during fermentation.
Fermentation This stage of the process is where yeast is introduced to change the sugars from the grapes into alcohol. Some winemakers innoculate the grape mass with a known yeast such as Saccharomyces cerevisiae. Others choose to use the wild yeasts that naturally have accumulated on the grapes in the vineyard. An optimum temperature about 25°C must be maintained during alcoholic fermentation to facilitate the growth of yeast and to extract the desirable flavour and colour. The result product can be up to 18% alcohol depending on the amount of sugar metabolised. Fermentation can take place in stainless steel vats or wine barrels, and can take 10 to 30 days to complete.
Clarification The clarification process begins once the fermentation process is completed. Some suspended materials like spent yeast cells, skin fragments, and other unwanted solids makes the wine cloudy and gritty. Clarification can be done by racking, fining, filtration, centrifugation, refrigeration and/or heating. Racking involves pumping the liquid out of one vessel into another, leaving the solids behind. Fining occurs when a fining agents like bentonite, egg white, or gelatin are added to clarify the wine by adsorption, precipitation and chemical reactions. Filtration can be done using a filter pads made of cellulose fibres. The pore size of the filter controls the draining of large solid materials when juice is poured. Centrifugation may be applied to the wines that are difficult to clarify. Lower temperature prevents the yeast growth and evolution of CO2 and keeps the cell suspended and also speeds up the precipitation process. Pasteurization is done at 70-82°C to remove the cloudiness formed by the protein.
Ageing and Bottling Ageing, if carried out, is done in barrels. The barrels do several things—they can introduce more chemical components to the wine, altering or adding to its flavours, and they can also encourage other chemical changes by allowing small amounts of oxygen into the raw wine. Bottling Before the wine is poured into bottles several processes can be employed to fine-tune the quality of the wine. The wine may require blending with other wines, a final filtration to remove unwanted particles, and use of substances to combat microbe development. Bottling may be done at the winery or by bottling contractors. Appropriate storage conditions must be maintained while stored in the bottle i.e, 12-16°C in a dry and stable place.