Global warming is defined as the increase of the average temperature on the earth. However it encompasses many factors from drought to increased precipitation and storm surge, rising sea levels, increased incidence of pests and disease among others. Everyone seems to agree that the earth’s temperatures are on the rise and storm cycles have increased both in number and ferocity as climatic changes have occurred. Admittedly there are arguments as to the cause of these changes, but prevailing science seems solidly on the side of man’s intervention in the atmospheric conditions of today.
The rise in temperature at an international level over the last few decades has serious effects on the agricultural production and, by extension, on viniculture. Wine is perhaps the most universally recognized beverage with a history that dates back to 8,000 BC. Though many of the viticulture practices have remained the same, the earth’s climate has not. There is an intricate and complex relationship between climate and wine, but one that is necessary to understand in order to produce high quality wines. Climate is a major factor in vine cultivation and understanding the local character of wine typicality.
Depending upon the location (terroir), climate change will likely affect grape growing and winemaking somewhat differently. We know that wine regions of the world producing some of the best wines are specific areas that fall in between the 30th and 50th parallels. This is because, as crops go, quality wine grape vines are extremely fussy. They need a cold – but not too cold – winter. They need a mostly frost-free spring during which their buds can safely emerge. They need a long, sunny growing season and eventual temperatures that are fairly warm – but not so hot that the grapes will sunburn or ripen too quickly. They need a fluctuation between daytime and night time temperatures, which enable the development of compounds that eventually become the complex flavours in a fine wine.
Mediterranean-type zones share certain characteristics that lend them a special distinction among the world’s landscapes. Sun intensity is high, especially in inland areas, due to clear skies and low humidity. Summers are warm to hot, and winters are cool but mild.
To understand the climate’s role in growing wine grapes and wine production, one must consider issues such as the weather and climate structure and variability, both seasonally and long-term, of the region under consideration, as well as the influence of climate change on the structure and suitability to different wine grape cultivars. These issues are not easy to investigate as one can realise in figuring out which grapes perform best, because it takes five to seven years for a newly planted vineyard to begin producing grapes suitable for winemaking.
The climate of a wine region ultimately determines the style of wine produced, but year to year variability can also have a more immediate impact. Warmer years tend to produce wines with higher sugars, but less acidity and tannins, while a cooler year will tend to produce a more acidic wine, but may lack the necessary sugars or balance. A year with excess precipitation may produce diluted or less robust grapes, while an extremely dry year may actually cause a minimal crop harvest.
Although the role of the dormant phase of the growing season for grapevines is not fully understood, we know that winter dormancy affects the vine’s vegetative and berry development. A dormancy period helps to synchronize the growth stages for vines. It avoids irregular and patchy budburst or maturation for separate plants. In addition, the existence of a dormant period substantially increases the productive lifetime of the vine. Temperatures during bloom appear to play a crucial role in fruit-set, ovule fertility, and berry size. Warming above a cultivar-specific optimum reduces crop yields. Spring frosts that injure developing shoots, and frosts after budburst that reduce the current season’s crop yield, are among the most common detrimental effects of minimum temperature extremes. Similarly, extreme maximum temperatures in summer can cause substantial heat damage by inhibiting photosynthesis and causing sunburn. Exposed grape bunches are particularly vulnerable to heat damage during the ripening stage.
During ripening and change in berry colour and maturation, temperature affects sugar content, acidity, colour and flavour profile of the berries. In general, high temperatures increase grape sugar accumulation (and thus potential alcohol), and reduce grape acidity. This determines the style, balance and potential alcohol of the wine. In addition, during a process called “flavour ripening”, various enzymes initiate the physical softening of the berries and, most importantly, contribute to the accumulation of flavours, aromas and pigments. Enzyme activity follows an inverse U-shaped pattern and is low at low average temperatures, high at moderate temperatures and falls again at high temperatures. Very high temperatures can inactivate or even irreversibly destroy any enzyme activity.
The physiology of the vine is very sensitive to any climatic change and this is reflected in how it reacts in fluctuations of the weather producing different results every year. The quality of production and the genuineness of the wines is reliant on a system of interactions between the climate, the local environment and the produced variety within a defined geographical area. Climate is possibly the main factor influencing the wider potential of an area as to the prosperity of each vine variety and the production of a certain type of wine.
In addition to changes in the physiological development and growth of the grape vine, increased pressure from pests and other diseases will also become more prominent as time goes on. Like grapevines, insects and pests also have ideal temperature ranges within which they can grow, survive and propagate. As global temperatures increase, we should also see a shift in the range where different pests and insects can flourish and thrive.
An increase in temperature may increase the vineyard’s susceptibility to Grapevine Moth and powdery mildew. Climate change and global warming will force vineyard managers to be increasingly vigilant in identifying and then managing a variety of warmer-weather-bound insects and diseases. Changes in temperatures and humidity may increase the presence of insects and insect-borne diseases. Many regions, long believed to be climatically protected from certain pests, may now find themselves open to infestation and contagion.
The amount of precipitation that a vineyard receives is important to the suitability of the site to be able to produce a quality grape. Most importantly, it is vital to the health and success of a grapevine that the soils do not become water logged, as this not only promotes root rot, but also causes physiological differences in grape development.
The temporal distribution of the total amount of precipitation is the biggest factor of the precipitation component. Increased precipitation can cause grape berries to swell and split, which would compromise the quality. In addition, precipitation that occurs just prior to harvest can affect Brix (the unit used to measure sugar content) by diluting the sugar content and causing the Brix to drop, which would then result in the production of less alcohol during fermentation. Viticulturists perpetuate the theory that excess precipitation (particularly in September/October) is harmful by supporting the notion that water deficits may actually increase the quality of the grapes. Vines that experience water stress have been found to actually produce fewer and smaller grapes, but with higher phenolics, thus higher quality. Extreme water deficit is harmful to the development of the fruit, so precipitation amounts do need to be monitored in order to determine if irrigation is necessary. The water balance of the vine is mainly determined by local precipitation (rain, snow), ambient atmospheric humidity and soil water holding capacity.
On the demand side, rain plays a decisive role in the vine’s water requirements. The overall quantity of annual rainfall and its distribution over the growing and non-growing season is crucial when vines are not irrigated, as is the case in almost all of Europe. When vines are irrigated, water supply can be optimized and adjusted to the plant’s needs. In general, while ample rainfall during the winter and the early vegetative stage is beneficial, rain during bloom and maturation is deemed detrimental.
Though grape growing in dry climates allows more control of vine growth by managing irrigation, it may be difficult to find enough water. As a result, when replanting, growers are adopting more drought-tolerant rootstocks. Lack of rain isn’t the only issue. Wet weather now seems to come at inopportune times: harvest or budding. One year, we get all our rain in a short length of time whilst another year we have many small rainfalls.
Considering the particular case of viniculture in Cyprus, vineyards for grape cultivation and wine production can be found all over the Troodos mountainous region. Climate change, which for Cyprus translates into higher temperature and less precipitation, poses a threat for the future cultivation and production of high quality wine. Moreover, the extent of cultivated areas is a major constraint. As one of the smallest European countries, Cyprus does not have large areas of land for cultivation. If the pattern of cultivatable areas for grapes changes, it could lead to the decrease of their availability. This poses a huge problem because without land for cultivation, technology will not be able to help.
According to scientific studies, if nothing is done to reduce global greenhouse gas emissions, vineyards will be displaced more than 1,000 km beyond their traditional boundaries by the end of this century, radically jeopardising the wine-growing industry. Increasing temperatures will also cause further damage.
What has taken centuries to create is now at risk of being eradicated. There is evidence already of changes in grape and wine production from the last two decades; the next four decades of this century will bring many more. While the exact magnitude and rate of climate change in the future is unknown, history has shown that climate and wine are intricately linked. Addressing climate change effects on viniculture and wine production and taking action is of critical importance for the economic health of any wine producing region. An increase in temperature is inevitable, according to the climate projections. What these increases mean in terms of wine grape quality cannot necessarily be exactly measured, since there are so many other parameters entailed in producing a quality grape, but there are several effects that can be determined. Consequently, collaboration between scientists, growers, and government agencies will be necessary to maximize participation in any climate change adaptation programmes.
Concluding this short note on the impact of climate change on wine, one has to acknowledge that over thousands of years, grape growers and winemakers have proven their adaptability to changing political cultural, climatic and economic environments and are likely to do so in the future as well. Wine producers have adapted to the changes and the vine has a capacity of adjustment that you can find in no other plant. The wine world will change, although less quickly than the climate, owing to human resistance to change. Vineyard owners are moving their grapes to higher altitudes and harvesting the grapes at different times during the season, or in different ways, than they did before. Furthermore, wine production is a common cultural heritage built over time through specific regions, countries and traditions. Ensuring a better protection for this unique heritage is in our common interest. So, raise your glasses in a toast to the unknown future of wine, reminding yourself, with a slogan borrowed from the peace movement, to “think internationally, act locally”.