Wine grapes ripening up to two days earlier each year, as viticultural experts warn some traditional varieties may be abandoned in warmer areas

Wine grapes in Australia are ripening between one and two days earlier each year due to climate change in a trend viticultural experts say could see some traditional varieties abandoned in warmer areas.

The Victorian wine industry is partway through what could shape up to be its earliest vintage on record, thanks to an exceptionally warm spring and warm summer.

Grape growers are also experiencing a compressed vintage with typically later-ripening red grape varieties demanding to be picked at the same time as earlier varieties such as chardonnay, causing congestion in the crushing bay as three months of grapes arrive in three weeks.

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Snow Barlow, honorary professor of agriculture and food systems at Melbourne University, said vintage dates had been shifting forward at a gradually accelerated rate over the past 30 years and the trend was set to continue, with grapes ripening an average of seven days earlier for every degree the climate warmed.

“They clearly are the canary in the cage,” he told Guardian Australia. “You can say what you will about climate change but the plants don’t lie, they just react to what they feel, and they are reacting again.”

A 2011 study by Barlow’s Melbourne University colleague, Leanne Webb, examined the vintage records of 44 vineyards, some of which went back as far as 115 years, and found that grapes had ripened at a rate of 1.7 days a year earlier between 1993 and 2009.

A later study, led by Webb and co-authored by Barlow, found that change was driven by a warmer temperatures and lower soil moisture content, even accounting for an industry-wide shift towards picking earlier to get low-alcohol wines.

“It does mean that for particular varieties you really do have to think about moving,” Barlow said.

“It sounds a bit ho-hum in some ways but the climate is changing and you really do have to analyse carefully when you are looking to set up an agricultural enterprise not only whether this is the place to do it now but whether this is still going to be the place to do it in 25 years time – whether you are going to have access to the water you need in 25 years.

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“The South Australian wine companies are looking at the Adelaide Hills and thinking well, do we really have enough water there?”

The same trends have been observed in Europe, where records have been kept by generations of winemakers since the 1500s. The information is a valuable indicator of climatic change – there is an extensive global dataset noting the picking dates and, in later decades, the sugar levels, or Baumé, of individual vineyards.

“Where it differs a bit in Europe is that for the most part they have probably pushed the boundaries a bit more than we have but more toward the cool side, so when you look at Bordeaux or look at Champagne and the worst years are sort of the cold and wet ones,” Barlow said. “So they’re talking about it as something that will help.”

In Australia it’s the opposite effect: warm springs and hot summers can produce lower-quality wine, and if they’re coupled with bushfires there is, Snow said, “bugger all you can do” to save the wine being tainted by smoke.

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Damian Sheehan, chairman of Wine Victoria and general manager of Mount Langi Ghiran winery in the Grampians about 190km west of Melbourne, said grapes that ripened quickly risked “decoupling” their sugar and acid content, which meant they reached the desired alcohol level before the flavour was developed.

“You have just got this very, very high (indicative) alcohol content and you want to make sure that you manage it so that you don’t end up with high alcohol wines,” he said.

“You do start acclimatising and you start knowing what you are going to do to make sure that the alcohol levels are what you want to produce.”

Sheehan said they would not know if it was a record early vintage until after the season ended, but that most vineyards appeared to be picking early.

He said a number of companies were planting Spanish or Italian reds, rather than traditional French varieties, to cope with the warming climate. Others were looking to expand into cooler climates such as Tasmania.

Andrew Weeks, executive director of Wine Grape Growers Australia, had not noticed the early trend, saying 2016 was “probably the most un-uniform vintage I have ever had anything to do with”. His own cabernet sauvignon vineyard in South Australia’s Riverlands was harvested at its usual time.

Weeks said climate change fell behind economic challenges on the concerns listed by most growers he spoke to who worried about “whether the policy settings will see them viable in one to two years’ time”.

“If you have got that sort of time frame, it’s hard to be concerned about what the climate might be doing in 20 or 30 years,” he said.