Climate warming will lead to better wine | COSMOS magazine

LONDON: Grapes grown in the wine regions of Australia are ripening earlier due to warmer climates and dehydrated soils.

The finding could help wine growers adapt farming practices to improve the quality of their wine in the future.

For the last few decades wine grapes across the country have matured earlier and earlier, with grapes in Southern Australia ripening around eight days earlier every 10 years. Early maturation and ripening can result in a lower quality of wine.

"The balance of flavours, aromas and sugar levels are affected by the climate conditions during ripening, therefore, changes in timing of maturity can change the style of wine that is produced," explained Leanne Webb, lead author of the study published in the journal Nature Climate Change this week.

"These changes may be important where regional wine characteristics are well understood, and often anticipated, by wine consumers," said Webb, from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Marine and Atmospheric Research.

Warming explains early wine ripening

In order to identify the factors driving this change, Webb tested the assumption that earlier ripening of wine grapes was due to observed regional warming. The team modelled records of wine grape maturity from 10 vineyards in five regions located across Southern Australia over a 64-year period.

"In contrast to previous studies that use harvest dates to indicate grape maturity, we examined berry-sugar concentration records to detect the trends to earlier wine-grape ripening," said Webb. "Environmental variables and management input that were likely to affect ripening rates were considered."

Having modelled the data, Webb found the two key variables determining grape ripening to be climate warming and a decline in soil water content.

"What we found was that only about a third of the shift was driven by regional warming," said Webb. Other factors contributing to the early ripening included crop-yield reductions and evolving management practices, she said.

Making better wine

The research could help growers maintain wine quality under changing environmental conditions, as the drivers identified can be manipulated through management of farming practices.

"By understanding what is driving this plant response we have revealed some adaptation initiatives that would not necessarily have been considered before and provide useful insights into how to maintain wine quality under changing environmental conditions," said Webb.

"Conceptually, this study may inform studies in other sectors where similar results would also be useful in responding and adapting to potential climatic shifts."

Terry Bates, a viticulturist at Cornell University in Ithaca, New York, warned that the range of factors influencing grape growth are wide and complex, however, limiting the extent to which the work can directly help wine growers adapt.

"The complexity of interactions in a perennial cropping system and the lack of an adequate long-term data set are two of the reasons this has been such a difficult question to answer," commented Bates. "This article adds to the evidence that climate change is potentially advancing grape maturation. However, I would caution the speculation on the practical magnitude of this influence without more detailed phenology or yield component information."

While the findings are useful to the Australian wine region it's a different story for other wine growing areas, he said.

"Quality is a subjective term in the grape industry," added Bates. "Advancing maturity in warm production regions may be negative, but the same advancement in cool regions may be positive to the wine maker."