Heat rises hit grapes

Declan Bush
Heat rises hit grapes

Predicted rising temperatures in the Margaret River region in the next few years are expected to have a significant impact on the quality of wine grapes, with early maturity an increasing concern.

Curtin University associate professor Mark Gibberd said a new study of WA's wine regions showed a "demonstrable" change in grape maturation.

"There is definitely an advancement of maturity," he said.

Dr Gibberd directs the Centre for Crop and Disease Management and said the study observed the impact of climate change on grape maturation, colouring and acid profile.

The report said under existing management practices, some of the key grape attributes integral to premium wine production would be affected negatively by a warming climate, but the magnitude of the impact varied across the established wine regions, varieties, the magnitude of warming and future periods considered.

"There is a lot that the industry can and will do to adapt," he said.

"We anticipated that there will be changes to seasonality.

"We expect a shorter season and, in some cases, a slightly earlier bud burst."

He said changes to irrigation and canopy management could help growers manage temperature increases. He said growers in "very southern areas of Margaret River" would benefit from the rises.

"A small change in temperature will actually assist those growers," he said.

Dr Gibberd said rising temperatures changed the balance of sugars and acids in grapes as they developed.

He said the hotter temperatures could cause grapes to "lose some of the balance between sugar accumulation and the development of flavours".

AHA Viticulture senior consultant Jim Campbell-Clause said rising temperatures for the past eight years had made earlier vintages "pretty well the norm".

"The trend is a warming trend," he said.

"We seem to be harvesting much earlier than the long-term average."

Mr Campbell-Clause said rainfall, customer tastes and viticulture practices affected timing of the vintage.

Viticulture consultant Bruce Pearse said winemakers changed their methods to account for seasonal differences in temperature.

"There's a fine line between viticultural factors and weather conditions," he said.

"It really just depends on weather conditions between flowering and harvest."

Mr Pearse said the rising temperatures, a drop in rainfall and more evaporation would affect the industry in general.