FOOD & AGRICULTURE
In the second part of the 21st century, more invasive adaptations, like severe reductions in leaf area to fruit weight ratio, or the introduction of non-local, later ripening varieties will, most likely, be unavoidable6
Cornelis van Leeuwen Bordeaux Sciences Agro 2%
Percentage points increase in alcohol content of wine attributed to rising temperatures as a result of climate change since the 1980s
Changing exposure of vines to UV-B radiation in recent years can also affect wine quality. In the right amounts, this part of sunlight creates desirable flavour compounds in grapes, but excess UV-B can produce off-flavours in white wines and even ‘sunburn’
are harvested around two weeks before the traditional dates. In the Champagne region in France, harvest kicked off on 26 August 2017, while the average date for previous years was 10 September. In Bourgogne, home of Beaujolais wines, harvest began on 23 August, two weeks ahead of schedule. Harvest workers in that area are also doing night shifts to reduce heat stress for the sensitive grapes. Both phenomena, the success of English wine and the earlier harvests in France, are linked to climate change. A fact that Barrie and Richards omitted to mention in the Waitrose article. They are also linked to each other. In a few decades, the favourable wine-growing conditions historically enjoyed by the Champagne region may have migrated to England. As the life cycle of the grapevine, and quality and quantity of the wine obtained, are extremely sensitive to temperature and weather extremes, wine growers have already been noticing the effects of climate change for years. Researchers have detailed how conditions have changed, how they are likely to change further, and what vineyards can do to adapt.
High value product All agricultural products are likely to be affected by climate change at some point, but wine occupies a special position due to its high value. Therefore, wine growers have always watched the weather and its effects on their vineyards very closely, and recorded their observations.
Climate scientist Benjamin
Cook from Columbia University at New York and ecologist Elizabeth Wolkovich from Harvard University, have analysed harvest data spanning more than 400 years, from 1600 to 2007, from seven regions in France and one in Switzerland, together with the weather data.1
temperatures have generally been sufficient for an early harvest regardless of the rainfall. In the past, earlier harvests were
While many studies
have covered the last few decades, this one reaches back to the time before the Industrial Revolution, thus establishing a baseline measured before the onset of man-made climate change.
The time of the harvest is
determined by the ripening of the grapes. The life cycle or phenology of the grape normally lasts around 180 days from the appearance of the first buds to the point at which grapes are ready to be picked. Higher temperatures in spring and summer generally speed the whole process and lead to earlier harvests, like the one in 2017, while cool and rainy summers can delay the phenology and thus the harvest time. Traditionally, the observation was that a warm summer and a period of drought just before grape picking is the best recipe for an early harvest. The data analysed by Cook and
Wolkovich show that the harvest dates follow these rules and oscillate with the weather for most of the period studied. The most prominent spikes in their graphics are the ‘year without a summer’ of 1816, when the eruption of Mount Tambora in Indonesia shrouded the Earth in a veil of ashes and led to a noticeable cooling effect, and the extreme heat wave of 2003, which brought harvests in Western Europe forward by more than a month. Climate change becomes obvious in the charts post 1980. The curve leaves the range of the previous standard deviation and takes a sharp turn towards earlier harvests. All annual harvests since 1980 have taken place before the historical average date. The authors explain this turn
as a decoupling from the drought requirement. Previously, a late drought was needed to give the grapes the last push towards an early harvest. At least in part, this effect was due to the higher local temperatures above dry ground, in the absence of the cooling effect of evaporation. Since 1980, rising
generally welcome as they often yielded better quality wines. However, as Wolkovich points out, there is a limit to this beneficial effect. For instance, the extremely early harvest of 2003 is not generally known as an exceptionally good vintage. Thus, if these extremes become the new norm, wine growers are likely to feel negative consequences. ‘Our research, and other work,
has clearly and unequivocally demonstrated that climate change is already affecting viticulture worldwide,’ explains Cook, adding: ‘There are lots of opportunities for adaptation in various locations, such as planting different varieties, but the most important thing is for people to starting planning for the next several decades, when conditions are likely to get even warmer still.’
Grape composition Even wine growing areas that have so far felt benefits of the warmer climate have reasons to worry about their future as temperatures continue to rise and the frequency of extreme weather events increases. The regular hurricanes in the Caribbean are becoming deadlier with higher sea surface temperatures, while the South of France has also suffered weather extremes linked to warmer Mediterranean waters. In a recent
review article, Cornelis van Leeuwen from Bordeaux Sciences Agro and Philippe Darriet from Bordeaux University, France, have summarised the known effects of climate change on wine quality and yield and attempted to extrapolate likely
24 09 | 2017
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
