In the third and (you'll be pleased to hear) final part of this series we get to the important part. In the first section we tried to quantify the effects of climate change on viticulture and winemaking. In the second we looked at defining the specific problems they caused. Which leads us now to 'What can we do about it?' Are there any solutions, or at least ways of mitigating the damage?
I'd like to start by discussing two apparently obvious but totally fallacious ideas: conversion to organic viticulture, and the use of irrigation.
The myth pedalled by advocates of organic agricultural practices is that they are better for the environment. This is demonstrably incorrect, and furthermore you end up paying over the odds for an inferior product. I have written about it at length in an article published by the excellent quarterly The World of Fine Wine - link here. If you can't be bothered to read it (although I obviously recommend that you do) I'll summarise the most relevant climate-related points here.
To quote L'Institut national de la recherche agronomique: ‘Le bio, c'est bon pour l'emploi.’ Why? Because, on average, organic production requires 50% more labour than conventional. Why? Because, quite frankly, it doesn't work very well and you have to do everything more often, from spraying to weed control, and it takes longer. To give an example from one French producer who converted his conventional vineyard to organic, he found that he was using one extra litre of diesel for every 50 bottles of wine he produced. The annual balance for his small vineyard was minus 8 litres of Roundup herbicide, at a cost of 400 litres of fuel. Some carbon footprint. When you consider that organic yields are normally considerably lower as well, the environmental cost per kilo of grapes becomes quite disturbing.
Roundup, by the way, even if accidentally swallowed, is about thirty times less toxic than caffeine and it is easily biodegradable.
I also want to mention, in passing, whether irrigation might be a solution to increasing temperatures and erratic rainfall patterns. In short, the answer is no. Irrigation is a terrible option for those trying to protect the planet. It is estimated that 120 litres of water are required to produce a single glass of wine - the vast majority of which is used in irrigating the vineyards. Vines that have always grown under irrigated regimes do not develop the deep roots of dry-grown vines, and suffer badly if the reservoirs used to sustain them dry up during a drought. Bear in mind that these same dams may well also be required for supplying drinking water to the local population.
I could go on for much longer, but if you're interested look up some of the irrigation-caused salinity problems in Australia in particular (they have had to breed new rootstocks just to cope with the damage inflicted on the soils). The answer is simple - plant grape varieties that have evolved in dry climates, and are naturally adapted to the conditions. When you consider that there is a global excess wine production of 30 million hectolitres per year (or five times as much as Portugal’s total annual crop) we just don't need to be watering the vines.
Fortunately we viticulturists are quite resourceful people, and we have worked out some ways of mitigating climate change in the vineyard. One of the easiest, and most obvious, involves a paradigm shift through 90 degrees, literally. Traditional (French) viticultural theory dictates that when planting a vineyard the rows of vines should ideally be aligned East - West. This means that the canopy catches maximum sunlight during the warmest part of the day, to assist with ripening. It works fine in relatively cool climates, as has been most of France historically, but during increasingly warmer summers it is a far better idea to establish a vineyard with a North - South row orientation. That way each vine is shaded by the one next door at the hottest time of the day, creating a far cooler microclimate within the canopy.
This is perfectly illustrated in the aerial photo below, showing two vineyards planted only 20 years apart.
Note the shade-friendly row orientation in the newer vineyard, to reduce sunburn.
As mentioned earlier, choice of appropriate grape varieties is obviously another solution. New World wine producing countries pioneered the use of homoclimes (regions in different hemispheres with similar climates) to determine which European grape varieties might be best suited to, say, Western Australia or Southern California. Existing wine regions which are becoming warmer could likewise look towards growing varieties from Greece, Italy, Spain and Portugal which have evolved to thrive in extremely hot and dry conditions.
Soil management can also make a huge difference. The trend away from intensive soil mobilisation and excessive use of herbicides has shown the benefits of mid-row cover cropping. It was assumed, wrongly, that other plants in the vineyard competed with the vines for water when in fact grasses and clovers find the humidity they require at the surface of the soil whereas the vines clearly have much deeper roots. At the end of Spring cover crops are mown and dry out naturally, providing a natural mulch. There are several advantages:
1) Reduced erosion during the winter because it slows down run-off.
2) After mowing in the Spring, the remaining stalks and roots actually help subsequent rainfall to infiltrate to depths where the water becomes available to the vines during the drier part of the year.
3) The shade provided by the mulch, combined with the fact that cut grass reduces the impact of wind on the surface of the soil, reduces evaporation of soil water dramatically. Thus vineyards with cover crops actually retain MORE water during the summer months.
4) Certain cover crop species, such as clover, are nitrogen fixers and can actually boost vineyard fertility.
There are plenty of other tricks up our viticultural sleeves that can be used against climate change (pruning techniques, vine training, cordon heights, plant density and spacing etc.) but there are also suggestions that judicious leaf removal at the right time of the year will reduce water consumption and delay ripening. Using kaolin sprayed onto the leaves as a reflective sunscreen has also shown promise.
And whilst not strictly related to wine quality, harvesting grapes mechanically at night can be beneficial for the environment. This is because the fruit arrives at the crusher much cooler, and doesn't need to be chilled down before fermentation. Controlling the heat load placed on a winery's tanks can use up huge amounts of energy - so anything which reduces the number of hours that the cooling system has to run is clearly an ecologically sound policy.
But what if all this viticulture isn't enough? Can the winemakers do anything to help in their wineries?
Some things are easy to correct, such as getting the acidity and the pH of the wine balanced - you just add tartaric acid (which is itself refined from grapes, so therefore perfectly natural). Refined grape tannins can also be added to improve the mouthfeel in wines made from overripe grapes. But they can't be added solely to improve the colour - although conveniently they also do that too, which is fine just as long as it wasn't your original intention. (Where do I find the winking emoji on this keyboard?)
The search for strains of yeast which yield lower alcohol during fermentation is another interesting area, ongoing. There also exists, of course, the fairly crude but age-old method of blending a high alcohol wine with a less strong one. Higher alcohol levels due to over-ripe grapes (see the previous article for a better explanation) remain the winemaker's biggest problem.
Scientific advances, however, now allow us to use complicated techniques with impenetrable sounding names such as nanofiltration, reverse osmosis and the spinning cone to actually remove some of the alcohol from wine - but the one thing they all have in common is that they are generally agreed to have some detrimental effects on wine quality. Recent developments with a filter made from a mysterious material called graphene show more promise, but have yet to be proven at a practical level.
But what's the easiest way to reduce the alcohol level in a bottle of wine? Simple. Just use the label. American legislation, amazingly, allows such a difference between the actual and the quoted alcohol levels that a bottle of wine listed at 12.5% alcohol could actually be anywhere between 11% and 14%. Oddly enough, this is just because the labels need to be submitted for state approval often before the finished wine has even been blended. For your information, European and UK law allows a 0.8 % shameless fib in either direction.
There remains one simple method, however, of ensuring that wines can be made from phenolically ripe grapes, but do not have too much alcohol. Pay attention now, because I am going to let you in on a big secret. What I am about to explain is totally illegal, so don't mention that I told you. Everyone in hot climates does it but no one admits to it, obviously. It's one of the biggest secrets in international winemaking.
First, I'll explain briefly about bleeding a tank (this part is still totally legit, and indeed an admirable practice). If you want to make a red wine bolder and more concentrated you must realise that the vast majority of the flavour is in the skins of the grapes rather than the juice. (This is why we pump over, dunk the cap, and rack and return during fermentation. It's all about extraction of colour and aromatics from the skins.) However, the free-run juice itself is basically little more just a pale solution of natural sugars in water. In other words, bleeding immediately after crushing sacrifices some quantity for improved quality in what remains.
The (almost) exact opposite of bleeding is dilution. By adding water to the must before fermenting you would produce a greater volume of an inferior wine, which is why obviously this is totally forbidden. But you would of course have diluted the alcohol somewhat, which is what we set out to do.
So here's the clever part: you combine the two (almost) opposite techniques, but unequally. First, bleed off, perhaps, 20 % of the free-run juice to concentrate the flavour intensity of the remaining must. (You can ferment this pale pink liquid to make rosé. Ever wondered why there is so much more of it around these days?). Now dilute the sugar-heavy and grape skin-rich liquid remaining in your tank with some, ahem, PSW *, but use less than the amount of free-run juice that you bled off. So, say, add back just 10 % of the volume. By this point, the net total concentration of your must is now 10 %, and you have also reduced the alcohol in the final wine by about the same amount. Result? A more intense, full-bodied and phenolically ripe wine but lower in alcohol. Everyone wins, consumer and producer alike.
This technique is used to produce many of the best hot climate wines in the world, by the way.
Ingenuity like this should be encouraged rather than banned, but you didn't hear it from me anyway.
* pure spring water