Vine bud damaged by the April 2017 frost. ALBURY ORGANIC VINEYARD
CLIMATE: CHANGE FOR THE BETTER, BUT PROBLEMS COME TOO
ON A GLOBAL SCALE, CLIMATE CHANGE IS TERRIFYING. On a smaller, local-to-the-UK level it is popularly considered to have made a welcome difference to wine grape-growing. But that difference is nowhere near as much for the good as it might initially appear. Higher summer temperatures are valuable, but other aspects of the change are much less favourable to UK wine producers. Our climate is increasingly given to extremes – sudden late frosts, extra-strong winds, rain in damaging deluges – and any one of these can be devastating to vines. Consider two examples. In 2012 record rainfall during flowering severely limited fruit set and was followed by further rain at harvest time that rotted much of the surviving yield. Many estates – of which Nyetimber was the most renowned – made no wine at all from the vintage because the quality of the remaining grapes was too poor.
In 2017 a warm and sunny early spring saw vine buds opening a fortnight or more ahead of the norm. Then in the last week of April air frost down to as low as minus 6 degrees celsius scythed through the south of England, destroying much of the new growth and leaving vineyard managers to rely on the development of secondary buds to salvage at least some grapes to harvest. Some estates lost 80 per cent of their potential harvest while others were hardly affected at all. Intriguingly, ‘not a bud was touched’ at one of the UK’s most northerly vineyards, Leventhorpe, on the outskirts of Leeds, reported owner George Bowden.
This double-edged effect is widely acknowledged. When researchers from the University of East Anglia’s School of Environmental Sciences began to delve deep into the relationship between climate change and English wine in 2014, they appealed for information from all grape-growers and producers in the UK. Of the forty-two who completed the questionnaire – their 313 hectares of vineyards represented 17 per cent of the planted area of the time – 66 per cent said that climate change had, either definitely or possibly, contributed to the growth of the English wine industry. Yet, in response to a second question, asking whether they saw climate change as a threat or an opportunity, 64 per cent viewed it as a threat and a further 29 per cent considered it both a threat and an opportunity. Only the remaining 7 per cent saw climate change as an opportunity. The pessimists quoted such problems as extreme and unpredictable weather, a growing gulf between good and bad years, wind affecting physiological development, and increased disease pressure due to warm and wet growing-season weather and milder, wet winters. For the optimists, among the good points of climate change were the broader range of viable vine varieties, later harvest dates and warmer growing seasons improving yield and quality.
Vine bud damaged by the April 2017 frost. ALBURY ORGANIC VINEYARD
The ‘apparent contradiction’ of these replies could be explained, the researchers suggested, ‘through producers’ perceptions of increasing average temperature being accompanied by extreme weather events, which they attribute to change, contributing to low yield in some years’. Further understanding of that dichotomy became a key element of the continuing investigation.
Much as I’d like to summarize here all that the team, led by Alastair Nesbitt, discovered, doing so isn’t practical – there is too much else to cover. But some findings in the report, published in 2016, are very relevant to understanding the natural forces at work on present viticulture in the UK and what the future may hold. They confirmed the gradual rise in average temperatures in the growing season, April to October, from 1954 to 2013, with temperatures in southern England since 2004 frequently at least one degree above the 13 degrees celsius minimum needed for high-quality cool-climate wine grape production. (The post-2004 English temperatures are similar to those in the Champagne region through much of the second half of the twentieth century; the French growers are now facing rather more heat than they would choose, their grapes losing some of the acidity that is so crucial in making fine sparkling wine.)
Less comfortably, the research showed that temperatures in April and May have risen considerably more than the full-year average increase, encouraging the vine buds to burst open earlier and thus meaning more damage can be done by late frosts. Although these are a little rarer, they have certainly not disappeared – there was no year during the study period without at least one day in late spring when temperatures in southern England fell to a level that could harm opening buds, and these late frosts have continued since 2013. Also, the amount of rain falling in June has continued to be unpredictable, leaving unchanged the ‘constant threat’ that too wet a month poses to flowering, fruit set and eventual grape yield. And, warmer and wetter conditions at harvest time in October are bringing potentially more risk of disease affecting the grapes.
In essence, the general rise in growing-season temperature resulting from global warming has only a little to do with the quantity of grapes currently harvested in the UK. The continuing variability of the climate, most importantly at the crucial moment of flowering but also at bud burst and harvesting, is the major reason for the hefty fluctuations in yields from UK vineyards. In the very best years these can approach 30 hectolitres per hectare (approximately 4,000 bottles from an area the size of one and one-third football pitches), but in the worst years they struggle to reach a sixth of that. The average is around 20 hectolitres (2,700 bottles) per hectare. That same weather variability also significantly affects the quality of grapes harvested.
And one conclusion must seriously concern all those investors who in recent years have poured huge amounts of money into planting vines for sparkling wine. Alastair Nesbitt and his colleagues note the evidence suggesting that many of the grape varieties initially planted in the great UK wine revival are rather less vulnerable to poor weather than the recent favourites, chardonnay and pinot noir. Their warning is clear: ‘As a result, the sector [sparkling wine] is now at greater risk from variability in average growing season conditions.’ Perish the thought, but too many more years like 2012 might bring the downfall of some rather big names.
Rain in June remains a constant threat to flowering vines. ALBOURNE ESTATE
All vine-growers in the UK are vulnerable to weather variability, the report concludes, and they recognize that. But there is hope: ‘For those investing in UK viticulture, climatic risks may be ameliorated through management strategies, market forces and their ability to cope with lower-yielding years. Projections for future climate conditions in the UK will support future risk analysis.’
What is unlikely to happen in this maritime climate is weather as extreme as that seen in some other places in the wine world. Grape vines survive cold temperatures – down to below minus 35 degrees celsius in the case of one American variety (as happens when faced with other challenges, non-vinifera vines are often sturdier than Vitis vinifera) – but an unusually cold snap can wreak havoc, as happened in the Finger Lakes region of New York State in January 2004. Vines that were already less than normally frost-hardy due to a combination of previous climatic factors were severely damaged or killed when temperatures fell to minus 25 degrees celsius. That cost the region’s wine industry upwards of $60 million. No one is yet predicting UK winters like that, fortunately.
Similarly, the other extreme – soaring growing-season temperatures – is unlikely to occur immediately in the UK, but even a gentle increase can have adverse effects. Kevin Sutherland, winemaker at Bluebell Vineyard Estates in East Sussex, has worked in the English wine industry for close to thirty years, including a twelve-year spell teaching in the Plumpton College wine department. His prediction is that warmer, damper growing seasons will bring increasing problems for vineyard managers, with the appearance of diseases and pests never previously, or only very rarely, seen in UK vineyards. Destructive moths, for example, could fly in from Europe or hitch a lift on lorries, planes or ships, and become happily established immigrants. Vineyard managers will face greater challenges if they are to continue to produce quality fruit.
Kevin Sutherland: warmer, damper growing seasons will bring increasing problems. BLUEBELL VINEYARD ESTATES
But let’s not be too dismissive of the good effects of what is happening to the weather, argues Stephen Skelton, who in his consultancy role has played such an important part in the expansion of wine grape-growing in the UK. ‘Climate change has been behind much of the improvement enabling the UK to grow better quality varieties (chardonnay and pinot noir for sparkling as an example) and the quality of the “old” varieties that we still grow (bacchus, reichensteiner, seyval blanc) has also risen with the better sugar levels, lower acids and higher extract levels that you get with riper grapes.’ That is due not to higher daytime temperatures alone, but also to milder nights, which mean leaves warm more quickly as day breaks and photosynthesis can begin sooner. The vine has longer to produce sugar, and the result is higher natural alcohol levels in the wine.
Temperatures will have to rise a whole lot more, however, and weather variability will need to calm down, before UK grapes ripen to the heights achieved in much hotter wine regions. Red wine at 15 degrees alcohol from rondo or regent grapes isn’t likely to come from an English vineyard any time soon, and, while brandy and gin are increasingly made here from the final grape pressings, there is little possibility of a UK equivalent of port.
Look further ahead, to the end of the twenty-first century, and there could be a substantial change in both the varieties of grapes that do well in the UK and the locations of those that are already popular. Another 2016-published study, led by Professor Mark Maslin and Lucien Georgeson from University College London and commissioned by Laithwaite’s Wine, combined required growing season temperatures for individual grape varieties with models of anticipated climate change to create a grape map of the UK in 2100. On it, prime pinot noir and chardonnay growing areas move north to cover a swathe of central and eastern England, from Essex to north Yorkshire. Riesling and sauvignon blanc flourish over much the same area. The heartland of pinot gris is central England and the north-east, with successful plantings there stretching from the Humber estuary to the shores of the Firth of Tay. Syrah and malbec ripen happily around the Thames estuary and pYarts of the Severn Valley. Merlot and tempranillo cover that area and stretch further into Kent, Sussex, Somerset and East Anglia.
Other researchers have gone even further down the global-warming route, predicting that there will be parts of southern England – in Hampshire, Essex and Cornwall especially – where it will be too hot to grow wine grapes by 2080. Instead, they will flourish further inland, with red varieties pushing more delicate whites up to the hills or into Scotland. The most extreme suggestion is that by 2100 no vineyards at all will be left in the UK. That view wins little support in wine industry circles, but it prompted one commentator to urge action: ‘We must use this narrow window of opportunity to plant our vines and drink our liquid assets while we may.’
Bush vines like these in southern France won’t be seen in England for years yet. AUTHOR
Climate has effects beyond the choice of which vine varieties to plant. For example, it influences the style of training the vines, although the current changes are nowhere near substantial enough to alter radically what has been going on for decades. Those sturdy low-growing bush vines common in hot areas of southern Europe don’t have a place in the UK, where grapes need to hang high enough off the ground to avoid the disease-promoting dampness that rises from wet soils (hence the vital importance of planting on well-drained land). Two main training systems are used for British vines: Geneva double curtain and guyot. In the former, the vine trunk is divided at a height of around 1.5 metres and two canes are trained along parallel supports, with the fruit-bearing shoots – the ‘curtain’ – growing downwards; it works particularly well for vigorous vines, including many of the germanic crosses long favoured in the UK. Guyot is the world’s most popular vine-training system and is seen more and more frequently, as noble champagne varieties dominate the vineyards. It directs either one or two canes along a single supporting wire and from these canes the fruiting shoots grow straight up to further wires.
The space between the rows of vines is another consideration, as wider planting allows access by disease-deterring breezes. Discussion continues over the value or otherwise of leaf-plucking – removing leaves as the grapes grow, to allow more sunshine to reach them – and of green harvesting, when some of the unripe grapes are picked off to allow the remainder to ripen better. But decisions on many of these practices depend more on individual growers’ preferences than on marginal changes in weather conditions.
If climate change, then, is only a small part of the reason for the burgeoning of high-quality wine in England, what else is responsible? A lot of hard work is the simplistic answer. That work includes scientific studies such as that from the University of East Anglia team, which confirms to growers the climate changes they are seeing in their vineyards and gives them a valuable tool when planning ahead, and detailed site-specific investigation, such as the Plumpton College project. And it can extend down to such basic action as preventing damage from unavoidable late frosts.
Years back, the first time I visited sparkling wine estate Ridgeview, everyone was bleary-eyed from the loss of much of the previous night’s sleep. They had been out in the vineyard lighting ‘bougies’ – paraffin wax candles to boost air circulation around the newly budding vines and forestall the forecast frost damage. Nowadays, the preventive action can be much more sophisticated.
Bougies remain the frost-averting choice for growers who can’t afford the cost of bigger, more mechanised alternatives. But there is no need now for close attention to every spring evening’s televised weather forecast. At Albury Organic Vineyard on the edge of the Surrey hills, owner Nick Wenman and his daughter Lucy Letley are examples of growers who have frost alert alarms on their mobile phones, linked to a weather station among the vines. When frost threatens, the weather station sends a text message and they can be lighting their bougies ten or fifteen minutes later. They did that in April 2017, but the candles were of little use in air temperatures of minus 4 degrees celsius, and four-fifths of the open Albury buds were destroyed.
Bougies alight at Albury Organic Vineyard in April 2017 – sadly, they didn’t save the vine buds. SHEENAGH MCLAREN/ALBURY ORGANIC VINEYARD
At Gusbourne’s large estate close to the Kent coast, winemaker Charlie Holland likens his eight tractor-drawn frost-busters to giant hairdryers. Set in the coldest part of the vineyard, they suck in cold air using an aeroplane-type propeller, warm it and then eject it, creating protective air circulation. Also, as relative humidity reduces, the dew point is raised significantly and frost is less likely. The machines are better than bougies, Holland says, but still not effective enough when there is serious air frost. Even more impressive is Denbies’ import from New Zealand manufacturer Tow and Blow, a giant oscillating diesel-powered fan that rises up on a folding boom to nearly 10 metres above ground level and by its air-moving action can protect up to 6 hectares of vineyard. Yet again, though, this protects more against ground frost than air frost and some three-quarters of Denbies’ vines were damaged in April 2017.
Intervention like this, alongside more natural solutions such as choosing a breezy site rather than a frost hollow, or creating a ‘frost pool’ at the lowest point of a vineyard, can go a long way towards avoiding one weather problem for UK vine-growers. But there are no preventive measures against the effects of rain at flowering or harvest. Imagine massive retractable umbrellas unfolding over English vineyards . . . at the first puff of one of those increasingly windy moments they’d be blown away.
