Effects of warming climate revealed to wine industry

The latest and most in-depth Australian research into the effects of a warming climate on vine physiology, berry composition and wine attributes is revealed in a new final report, released to industry last month.

As well as presenting the Australian and world wine industry with a window into a future of hotter temperatures, the project suggests technological applications and adaptions in the vineyard and winery that could help industry adapt to warmer and drier futures.

The final 297-page report titled ‘A window into hotter and drier futures: Phenological shifts and adaptive practices’, is the culmination of a three-year research project, funded by the Grape and Wine Research and Development Corporation (GWRDC), Department of Agriculture, and complementary State Natural Resource Management Programs.

South Australian Research and Development Institute principal scientist Victor Sadras was project leader and said the project was both challenging and rewarding.

‘Critical to the research was the development of a new open-top heating chamber (pictured) which allowed temperatures to be manipulated under realistic vineyard conditions’, Dr Sadras said.

‘Much of the current research on this topic of temperature effects used either controlled glasshouse experiments or comparisons of different regions and vineyards, which made it difficult to correlate with real conditions and compare such contrasting data.

‘The new large scale open-top chambers were designed and deployed specifically for this project; chambers included a large number of vines, thus allowing for proper statistical design (buffer vines were excluded from measurements) and large fruit volumes for meaningful winemaking.’

It also combined passive heating (for clear days) and active heating (nights and overcast days) and regulated the size of the opening to conserve or release heat as required.

The first chapter in the final project paper outlines the design and physical application of the chambers, which have attracted significant international interest and continue to be used for ongoing research.

The chambers were designed to increase the temperature by 2°C above ambient temperature to represent warming projections for wine growing regions.

The field research in Barossa, was complemented with additional data analysis in Riverland and Coonawarra.  Four grape varieties were used in the project – Shiraz, Cabernet Franc, Chardonnay and Semillon.

There are 12 key outcomes of this project each briefly outlined in the report’s Abstract and further detailed in several papers included as part of the final project report.

In total, 39 scientific papers, industry articles, conference papers and workshops were written and presented to communicate the findings of this project. One of the papers, title ‘Elevated temperature decouples anthocyanins and sugar in berries of Shiraz and Cabernet Franc’ won the title of Viticulture Paper of the Year, awarded in 2012 by the Australian Society of Viticulture and Oenology for its “significant impact on the Australian wine industry”.

The project presents new research findings and outcomes regarding elevated temperatures on:

  • phenology
  • yield
  • anthocyanins and sugars balance
  • berry sensory traits
  • pH, acidity and wine sensory attributes
  • mesocarp cell death
  • stomatal conductance
  • dynamics of sugar accumulation
  • grape ripening

Despite the many ground-breaking results, Dr Sadras said it was the two wine-tasting workshops held to present the wine samples to industry for comment and feedback that remain a highlight of the project.

‘Not surprisingly, given the complexities of this industry and winemaking, we got very different comments from everyone who participated but it was great to see the level of engagement and interest’, he said.

‘Also, the project reached not only the large corporate component of the industry, but small and family operations, who attended and took something away from this project.”

With the continuing support of Dr Paul Petrie (Treasury Wines Estate) and GWRDC, Dr Sadras’ team has now started on his next project which delves deeper into the practical tools available to growers to mitigate higher temperature effects.  The new project brings in the expertise of Sue Bastian and Dennis Taylor (from University of Adelaide).

‘We found higher temperature will have – and is already having – the greatest effect on wine quality and the logistical issues around compressed harvest’, he said.

“Management practices at the vineyard and winery are required to counteract undesirable warming effects, so we have started to research using late pruning, on a rotational basis, as a practice to possibly counteract early on-set maturity of grape varieties.’

The full two-part report is available online.