Grape varieties adaptable
Viticultural production will be especially affected by climatic changes due to the strong relationships that exist between climate and winegrape quality attributes.
News story from 'Climate Change, A NSW Department of Primary Industries special feature', in The Land, October 2008
Dr Bruno Holzapfel, Wagga Wagga
The wide range of grape varieties available for production in different climatic zones shows the adaptability potential of grape production to altered climatic conditions.
Climatic changes in Europe have occurred over the centuries and have impacted on grape ripening. Harvest date records going back several 100 years reflect the climatic variation over the centuries and can assist in reconstructing past climate.
More recent data sets from over a few decades have shown advancement in key phenological stages and the harvest dates. In Australia harvest dates have advanced from half a day to three days per year between 1993 and 2006.
These observed changes and the projections of the impact of global climate change on wine production indicate the need for major adjustment in terms of the grape varieties and management practices employed.
Using a balanced global climate model forecast, mean growing season temperatures are forecast to be 1.5 to 2 degrees Celsius above 1990 levels by 2050 in most wine regions of NSW.
These projections indicate a number of consequences for grape production in the major warmer inland regions. Predictions on the impact on grape production are based on temperature changes and take little or no account of grapevine adaptive responses to predicted changes in carbon dioxide in the atmosphere or increased likelihood of water shortage.
It is predicted that the winter rainfall in the catchment areas of rivers supplying the irrigation water will be reduced by up to 10 per cent by the middle of this century, leading to potential reduction of inflow by 10 to 25 per cent. This would require a further improvement in water use efficiency for perennial crops.
The positive effect of higher CO2 levels on vine growth and water use efficiency might be reduced or completely cancelled by the negative effects of the predicted warmer temperatures associated with the increase of CO2.
Under such conditions a reduction of photosynthesis, higher respirations and shorter developmental stages will be likely responses. In addition, the increased temperatures will lead to earlier growing seasons, leading potentially to higher frost risk and sub-optimal growing conditions.
The further advancement of seasonal vine development will result in fruit maturation occurring at a warmer time of year. This will, together with a predicted greater likelihood of heat stress events, negatively influence the grape quality of currently grown varieties.
The plantings of alternative varieties with better suitability to the warmer conditions might present marketability difficulties.
The interaction between limited water supply and increased temperatures as well as seasonal and annual variation in both, will require a considerable adaptation and transition challenge for the Australian wine industry.
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