Global climate change is a major issue, because of its effects on the environment and the repercussions this is having and might have in the future. The effects of climate change on viticulture are constantly being researched and reviewed around the world.
Grape vines are very responsive to their surrounding environment with seasonal variations in cropping yields and wine quality each vintage. Climate is one of the key governing factors in grape and wine production, affecting the suitability of certain varietals to a region - as well as the type and quality of the wine produced. Wine composition is dependent on the meso-climate and the micro-climate - so for high quality wines to be made, a climate-soil-varietal equilibrium must be achieved and then maintained.
Most grape-growing wine regions are located between the 35th and 50th parallels in the Northern Hemisphere and between the 30th and 45th parallels in the Southern Hemisphere - (shown below). It is extremely difficult - virtually impossible to produce quality wine in tropical or sub-tropical regions.
With global warming the interaction between climate-soil-varietal will in different areas, come under threat from the effects of climate changes. The identification of the genes and underlying phenological variation in grape varietals has and will help to maintain consistent quality of varietals as conditions change - but not guarantee. The effects of global warming are expected to be more pronounced in the northern hemisphere and will change the margins and suitability for grape growing of certain varietals.
Climate data has shown that global temperatures are gradually rising with a linear warming trend - and this is anticipated to affect viticulture all over the world having both positive and negative effects on the various wine regions of the world.
Vine phenology; which relates to the date on which: bud burst, flowering and veraison (ripening) occur - is driven by temperature. Harvest has been taking place earlier because of increased temperatures. This has increased wine quality in many regions, because grapes can be picked when they are more fully developed. However, when ripeness is reached too early in the growing season (e.g. July or August in the Northern Hemisphere, and January or February in the Southern Hemisphere) grape composition can be unbalanced and the wine quality affected.
This has meant grape growers must adapt to climate change using various alleviating strategies. Adaptation strategies are needed to continue to produce high-quality wines and to preserve grape and wine typicity connecting them with their place of origin in a changing climate.
Adding to rising temperatures is the increase in carbon dioxide (CO2) concentration which is expected to continue to increase and affect grape vines. Changes in the amount of, distribution and seasonality of rainfall are also anticipated, as well as increases in surface level of ultraviolet UV-B radiation.
Temperature has a profound effect on viticulture as the temperature during the winter dormancy effects the budding for the following growing season. Prolonged high temperature can have a negative impact on the quality of the grapes as well as the wine as it affects the development of grape elements which result in colour, aroma, natural sugars, the loss of acids through respiration as well as the presence of other flavour compounds that give grapes their distinctive character.
Sustained moderate temperatures and minimal day-to-day variability during the growing and ripening periods are manageable. The unpredictable nature of climate change may also bring occurrences of frosts which may occur outside of the usual winter periods. Frosts cause lower yields and effects grape quality due to reduction of bud development and therefore grape quality benefits from frost free periods.
The grapes natural acids are essential to wine quality. The phenolic compounds such as anthocyanins and tannins which give the wine its colour, bitterness, astringency and anti-oxidant capacity. Research has shown that grapevines exposed to temperature consistently around 30°C have significantly lower concentrations of anthocyanins compared to grapevines exposed to temperatures consistently around 20-22°C. Temperatures around or exceeding 35°C are found to stall anthocyanin production as well as degrade the anthocyanins which are produced. The continuing increases in global temperatures will lead to a migration in ideal wine growing regions. It has been estimated that the northern boundary for European viticulture might shift north 20 - 30 kilometers over the coming decade with a possible further and faster movement if temperatures don’t find a new equilibrium. This has both positive and negative effects on viticulture, as it can open doors to new vineyards being planted and grown in certain regions but a loss of suitability of current viticulture and may also risk production quality and quantity overall.
Rainfall patterns will be affected - annually and seasonally - with rainfall occurrences varying in volume and frequency during the growing cycle. The lack of rainfall during key periods when it usually occurs, may result in drought conditions causing additional stress on grapevines. Rainfall is critical at the beginning of the growing season during bud burst - while consistent dry periods are important for the flowering and key ripening periods before harvest. Increased water stress reduces yields which has both positive and negative effects.
Increased CO2 levels will likely influence the photosynthetic process in grapevines as photosynthesis is stimulated by a rise in CO2 and has been known to also lead to an increase leaf-canopy area. A rise in leaf temperatures may alter the relationship with carbon dioxide and oxygen which will also affect the plants' photosynthesis capabilities.
UV-radiation will also reach high levels and this is known to impact upon chlorophyll and organic pigments development, which will decrease photosynthesis and effects the activation of natural genes which may alter aroma, colour and flavour compounds flavonoids and anthocyanins and therefore affect the character of the final wine.
Over the past 2-3 decades we have seen potential alcohol levels increase by more than 2% by volume across the globe, yes this has had some benefits, but if it continues, wines will start to loose some of their balance.
In the future, you will see more development and technology to try and manipulate the temperatures of grape vines. All the current and future techniques, can have some positive effects, while for other varietals, sometimes negative effects will follow. Any adaptation has a cost on the final wine. The wine you enjoy and even love has a personality and character, which is influenced by the climate in which it comes from. So possibly for some a good or another reason to do our part for the planet.