Winemakers labour to beat the heat of climate change

Australia’s big wine companies are battling to mitigate the effects of climate change pressuring their business.

Grapes that ripen too early may not develop ideal flavours. Picture: AFP/ Olivier Morin.

Neil Paulett, a winemaker in South Australia’s Clare Valley, stopped his vehicle in front of a row of vines on a recent rainy afternoon. The grapes growing here, he said, are ripening a month earlier than when he started the wine label that carries his name in the early 1980s.

More grapes are ripening at the same time, too, shortening the traditional harvest season by two weeks as it moves “insidiously forward,” said Mr Paulett, who traverses his vineyard in a white ute.

Some scientists attribute these changes to warming temperatures, which they say could pose a threat to winemakers globally. Grapes that ripen too early may not develop ideal flavours, and harvesting them later could lead to higher, unpalatable alcohol levels, scientists and winemakers say.

Some of Australia’s biggest wine companies, along with academics and researchers, are investigating ways to mitigate the impact. At stake are roughly 24,000 jobs in Australia’s winemaking and grape-growing industries, as well as wine exports valued at $2.1 billion ($US1.6bn) annually.

Treasury Wine Estates (TWE), which Euromonitor International says was Australia’s second-largest wine company by volume in 2015, is looking to prune more of its vines later in the year, a technique that can delay ripening. Taylors Wines, the biggest wine company in the Clare Valley and the 11th largest in Australia by volume, is also running its first trial of the delayed-pruning method and may one day apply the technique to 20 per cent of its vineyard.

Treasury Wine Estate CEO Michael Clarke

Taylors also expanded the size of its winery in recent years, in part so it can process more grapes at the same time and better handle the shorter harvests. Some vineyards are spreading more straw under vines to keep the soil cool.

If harvest times continue to move forward it would pressure winemakers further, said Andrew Pike, who runs Pikes Wines in the Clare Valley with his brother. “We’re just not going to get the flavour profiles that we’re looking for.”

Data from Treasury Wine show Cabernet Sauvignon grapes at vineyards in the McLaren Vale, south of Adelaide, ripened on February 4 in 2015, compared with March 25 in 1993.

Earlier ripening times have been reported across the globe, affecting some of the leading wine regions and presenting a continuing challenge to winemakers. In Washington state, warmer temperatures in 2015 prompted the harvest season to begin “historically early,” according to the state wine commission.

Other data from Treasury Wine show the ripening period in South Australia’s Barossa and Eden valleys was 24 days for certain Shiraz grapes in 2013, compared with 47 days in 1998.

“Very few wineries actually have the capacity to ferment all of their grapes simultaneously,” said Vladimir Jiranek, director of the ARC Training Centre for Innovative Wine Production, based at the University of Adelaide.

Grapes left too long on the vine continue ripening and accumulate more sugar, which yeast turns to alcohol during fermentation — so more sugar means more alcohol. That is a problem not only for flavour, but also because some jurisdictions tax wine at a higher rate if it has more alcohol.

Researchers with Mr Jiranek’s group have found combining certain types of yeast that are less efficient at turning sugar into alcohol with the standard wine yeast can lead to lower alcohol. Mr Jiranek says the researchers are now looking to develop new strains of less-efficient yeast to lower alcohol even further.

Grapes left too long on the vine continue ripening and accumulate more sugar.

Northeast of Adelaide, in the Barossa Valley, which is famous for its Shiraz, Treasury Wine will likely expand its delayed-pruning practices after conducting trials in recent years. For the 2016 harvest, some vine stems, where the grape bunches grow, were trimmed when they had two to three leaves, about the second week of October, compared with the traditional time of late May or early June. The method pushed back the harvest by 10 to 14 days, compared with the earlier pruned vines, staggering the picking so not all grapes ripened at once, without compromising the quality of the fruit, the company said.

“It’s a really simple technique,” said Gioia Small, regional manager sustainability for Treasury Wine. “There’s no additional cost. It’s just a timing issue.”

Technology does exist to filter out alcohol from wine, but some say the methods can be costly and are at odds with wineries’ marketing pitches as being naturally made.

Adam Eggins, chief winemaker at Taylors Wines, has another piece of advice: invest in bigger storage tanks, presses and other winemaking equipment. After a particularly short harvest in 2008, Mr Eggins said the company roughly doubled the capacity of its winery.

“I think at the end of it we stopped picking, because we just couldn’t get it in fast enough,” Mr Eggins said, standing in front of the imposing storage tanks that were installed after the 2008 harvest.

At the moment, the changes in harvests show few signs of reverting. Mr Paulett, of Paulett Wines, said that this year he left some early-ripening riesling grapes — the Clare Valley’s signature variety — on the vine for an extra week to develop the right flavours. On a drive through his vineyard in early September, he stopped by an old cabernet vine that had already sprouted a leaf.

“It’s a bit early,” he said.

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