Options for vineyards to deal with the trend of warmer growing conditions
By Sam Bowman
Climate change has emerged as one of the most confronting trends for the winegrape sector. As temperatures rise, the seasonal conditions affecting our growing regions may be shifting, challenging established ways of operating and thinking. Viticulturist Sam Bowman takes a look at what the research reveals, and offers solutions to consider for those growing vines.
Whether it’s cyclical over millennia or has been caused specifically by human intervention since the industrial revolution, there is one undeniable fact about climate change: it’s getting hotter.
Regardless of the climate (political or temperate), there is still a need to feed the world, produce goods and for most of you readers, grow grapes and make wine for the millions of thirsty palates around the world. How do we continue to thrive and produce our vinous staples in these conditions?
Background climate data
Since records commenced in the early 1900s Australia’s surface air and sea temperatures have increased by 0.9 degrees, our daytime maximum by 0.8 of a degree and overnight minimum by 1.1, not only increasing the overall temperature but reducing the diurnal shift grapevines enjoy during the growing season.
During the period between 1951 and 1980 very warm months occurred just over two per cent of the time. Between 1981 and 2010 this had increased to seven per cent and over the past decade to 2018 that percentage jumped to 10, meaning the extremes are worse, and more frequent.
We have seen an increase in the frequency, duration and intensity of heatwaves across the country in the last 50 years and this has brought with it a higher incidence of bushfire threat for many viticultural regions. The length of the ‘fire season’ has steadily increased since the 1970s.
With the increase in temperatures across the nation, the markers we use to categorise a region as ‘cool climate’ have shifted for many regions with only a handful of true cool climate regions still remaining (if we classify cool climate as a mean January temperature of 19 degrees and below).
“Varieties like Grenache, Mataro and Carignan have lots of potential viticulturally with a lower incidence of shrivel than Shiraz in heatwaves, proving great alternatives”
In the last 50 years the MJT of many regions has shifted upward more than a degree. Mildura has risen from 24 to 25.5 degrees Celsius, Clare Valley from 21.1 to 22.6 degrees and Naracoorte from 19.5 to 21.7 degrees, moving it from a cool to a warm climate.
These small changes can have dramatic effects on many facets of how we grow grapes and make wine in the country.
With these temperature shifts come changes to harvest logistics and the metabolic function of the vine as explained by AWRI research.
Earlier and more compressed harvest times, increased sugar concentration leading to higher alcohol wines, lower natural acidity and a change to varietal characters in the resultant wines are some of the changes we will see with increased temperature.
Under extreme heat (I use 38 degrees and above as my barometer) vine metabolism may be inhibited leading to reduced metabolite accumulations which may affect wine aroma and colour.
The high sugar content created can cause yeast stress during fermentation and can increase issues with ferment co-products such as acetic acid. With low acid comes high pH and a greater need for the addition of acid and microbial control during the winemaking process. No great news on the vineyard front for an increase in surface temperature.
So, what can we do to continue to thrive under the warming sun? Through years of hard financial times in the industry, grapegrowers have become savvy at adopting cost-saving measures in irrigation management, spray application and labour costs for growing large crops on a shoestring budget.
There is only so far a budget can be tightened without a compromise in the end product and the same goes for growing under extreme conditions; there is only so much we can do from a management perspective to control the effects of warming. So, if what we are doing on the ground can’t help, can we change what’s in the ground?
Rootstocks and clones
Yalumba Nursery has been driving change in the industry since its inception in 1975. It was initially established at Angaston in the Barossa, before moving in 2001 to its present site, a purpose-built facility near Nuriootpa.
Focussing on the identification of high quality clonal material through their own source blocks and their sole Australian distribution of ENTAV-INRA selections, Yalumba have a diverse array of varietal and clonal selections available to growers.
Varieties aside, their rootstock selection programmes and research are world class, offering solutions for all manner of climates. At the head of the operation is viticulturist Nick Dry who is driving the industry toward the adoption of high health, high quality and site-specific planting material.
Having discussed the issue of climate change and the implementation of certain stocks with Dry, his first port of call was the identification of water availability at each site.
“In a high rainfall year 101-14 will be a great stock, in warmer seasons with lower rainfall water management techniques will need to be employed to ensure good canopy growth,” Dry said.
“If the water source is not reliable, a different stock such as 1103 Paulsen or 110 Richter will need to be utilised and then managed for the higher rainfall seasons.”
Looking at clones and varieties, Dry suggested many options for early, mid and late ripening selections for different regions based on favourable harvesting conditions or for the management of staggered intake for large producers of mainstay varieties.
“Varieties like Grenache, Mataro and Carignan have lots of potential viticulturally with a lower incidence of shrivel than Shiraz in heatwaves, proving great alternatives,” he said.
Merlot is by far the most popular ‘unpopular’ variety in the country and Dry believes Merlot was let down by “compromised genetics and planting environments”.
With Merlot recognised around the world as a premium variety, there are a few key elements for its success.
“Adequate humidity, a soft climate and fertile soil along with improved clonal material will see success with Merlot,” he explained.
When queried on the future, Nick identified a clear shift.
“The future is non-varietal based labelling to utilise unpronounceable varieties and establishing regional blends. It put us on the map in the 80s and recently has probably held us back, [but] this will lead the way for disease resistant varieties as well.”
Dry’s last piece of advice was for anyone thinking of planting a white variety: “Just plant Albarino, its brilliant.”
Since becoming grapegrowers in the late ‘70s, and with the subsequent development of a nursery business in the late ‘80s, the Chalmers family have been drivers of innovation in the field of alternate varieties.
Nero d’Avola was first imported through the Matura group by Jenni and Bruce Chalmers in 1998, and since then the family have become a mainstay in the discussion of varieties to suit our changing climate.
After the sale of their nursery in 2008, the Chalmers family maintained their agency with the VCR cooperative in northern Italy to continue the sale of their proprietary material to Australian growers.
After a brief hiatus, Bruce and Jenni established vineyards and source blocks in Merbein in 2010 and Heathcote in 2008, and in 2016 re-launched their nursery operation specialising in the VCR and Matura material.
A new wave of Chalmers imports hit the country in 2015, many with desirable viticultural attributes for the changing vinescape.
Falanghina and Piedirosso from Campagna are exciting varieties according to winemaker Tennille Chalmers.
“Falanghina and Piedirosso have high natural acidity and are late ripening, making [them] a good option in regions with declining acids, they make approachable medium bodied wine styles without aggressive tannins.
“From our early maturity data off the mother vine, Falanghina showed a TA of 13.5 at 10 baume in mid-February in Mildura which is quite promising for acid retention purposes,” she said.
Along with declining acidity, warmer summers have also seen a decline in colour in warmer inland regions, something which is crucial for export markets.
VCR selections of Lambrusco Maestri have been popular amongst large wine companies for the deep colour, high acid, thick skins and neutral flavour.
Just ask Bruce Chalmers: “It’s bulletproof.”
With our reliance on the sale of single variety wines, blending options such as Lambrusco Maestri will become an important part of the game.
Alternative varieties have played a large part in the success story of Australian wine of late, but the big four are still accounting for the most substantial part.
According to Wine Australia data, 500,000 tonnes of Shiraz was crushed in 2017, 47% of the 1.06 million red tonnes crushed.
Shiraz was followed by Cabernet Sauvignon at 26% of the red crush, and Merlot at 12%, these three varieties alone accounting for 85% of the total red crush.
In the white department, Chardonnay is still king accounting for 42% of the total crush.
With much of our area planted to these four varieties, looking at other options in terms of clone, variety and rootstock when considering new developments is important for diversity and climate mitigation.
With further heatwaves making an impact this summer, none of us can deny the change. Like grapevines, growers are a resilient bunch and I’m sure will adapt to whatever comes their way next.