29 November 2012

Saving wine from climate change

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Wine regions risk losing their characteristic grape varieties as a result of climate change, but new methods developed in Australian vineyards could hold the solution.
Hunter Shiraz wine grapes

Shiraz grapes grown in the Hunter region of New South Wales, Australia. As populations begin to experience the effects of climate change, wine growers are coming up with novel ways to save iconic grape varieties. Credit: Stephan Ridgway/Wikimedia

MELBOURNE: Wine regions risk losing their characteristic grape varieties as a result of climate change, but new methods developed in Australian vineyards could hold the solution.

The wine industry in Australia is worth in excess of $5.5 billion but faces serious threats due to climate change.

Speaking at the Climate Change Research Strategy for Primary Industries conference in Melbourne, Australia, researchers have detailed their findings on how climate change is affecting grapevines, and a possible way to counteract the effects.

The Earth’s changing climate is influencing all aspects of grape production, according to Paul Petrie, of Treasury Wine Estates Ltd, including rate of ripening, sugar content and wine quality.

100% of seasons will be ‘extreme’

“Heating increased the rate of ripening,” said Dale Unwin, from the Department of Primary Industries Victoria, Australia, who used open-top chambers to monitor the affect of temperature on grapevines. These chambers worked like roofless greenhouses and allowed Unwin and his co-workers to increase the air temperature around the vines without altering other factors such as light or rainfall.

Unwin discovered the vines grown in higher temperatures went through all stages of development earlier than the control vines.

“Australia has the most variable climate in the world,” said Ian McClelland, chairman of the Australian government’s Managing Climate Variability program. The fourth assessment report from the Intergovernmental Panel on Climate Change predicts that 100% of Australia’s seasons will be ‘extreme’ by 2100, compared to today’s standards.

The disappearance of wine styles

One of the major concerns that climate change poses for vineyards is the change in harvest time, Petrie said. For every degree Celsius that the climate warms, grapevines in Australia are maturing nine days earlier.

This change in maturing times has shortened the harvest period for a single grape variety and has caused different types of grapes to mature simultaneously. This places great stress on the workers and infrastructure involved in harvesting, processing and transporting the grapes.

Petrie and colleagues have developed a method of ‘delayed pruning’ to lengthen the harvest season. Pruning the vines instigates bud development and so “delayed pruning offers the potential to delay the initiation of vine growth,” he said.

“An ideal adaption”

Using delayed pruning, Petrie has successfully postponed the ripening of batches of vines by up to three weeks. He suggested that by spreading out the pruning across vineyards costs may also be reduced as staff and harvest equipment can be used over a longer period, ultimately requiring fewer items of machinery.

“Delayed pruning is an ideal adaption option as implementation costs are low,” he said.

Petrie said he hopes this method will also help reduce the production of ‘unbalanced fruit’, which is where high sugar levels are reached before other qualities such as colour and flavour are optimised. This may impact fruit quality and wine style, he said.

In some areas, this change is so extreme experts are concerned that wine styles that typify a region may be more difficult to achieve in the future.

No significant effect on quality

Researchers with Unwin, however, suggested that “despite exhibiting symptoms of heat stress, the well-irrigated, mature vines used [in their study] were able to tolerate the generated heatwaves without detrimental effects on fruit or wine quality.”

Unwin also reported “no significant difference in the leaf function, or grape yield,” suggesting that well-established vines are able to adapt to hotter climates. However, “heat stress cannot be ruled out as only limited fruit sampling was possible.”

While the effects of climate change and delayed pruning on fruit and wine quality are still unconfirmed, the disadvantages of compressed harvest times are uncontested.

“Delayed pruning offers a real and cost-effective tool to allow the Australian wine industry to counteract some of the critical aspects of climate change, including compressed harvest and ‘unbalanced’ fruit and wine,” said Petrie.

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