KEY POINTS:
Climate change will enable New Zealand winemakers to grow grape cultivars further south and at higher altitudes than their existing ranges, says a senior climate scientist.
Wine styles likely to "migrate" south include sauvignon blanc - now grown in the Wairarapa and Marlborough - which is likely to be grown in Canterbury in 20 or 30 years, said Dr Jim Salinger of the National Institute of Water and Atmospheric Research (Niwa).
"The warming will allow the spread of the latitude range of wine styles further south, with red wines becoming more important in the east of the North island," he said in a presentation to the annual Romeo Bragato conference at Auckland yesterday.
But in the northern wine-grape regions a key issue will be whether, with the warming, there will be changes in rainfall and winter chilling.
"Should growing season rainfall increase, particularly in the autumn then there could be negative impacts on grape quality," said Dr Salinger.
Over the same period, cabernet sauvignon, merlot and franc cultivars grown in the Auckland region are likely to give way to types such as grenache and carignane.
There was likely to be a issue over vernalisation - whether Auckland winters would be too warm for grapevines which require winter chilling to trigger budbreak.
In the Gisborne area, chardonnay was likely to be replaced by shiraz, grenache and zindafel, while chardonnay and merlot were likely to be replaced by shiraz and malbec in Hawke's Bay.
Wairarapa's pinot noir could be supplanted by merlot, malbec and cabernet franc grapes while cabernet sauvignon and merlot were likely to replace sauvignon blanc in Marlborough.
In Canterbury, sauvignon blanc could replace chardonnay, while the pinot noir very suited to both Canterbury and Otago, could spread out to higher altitude sites in these regions.
Dr Salinger said climate change was an important issue for wine-grape growers, because vineyards have a life of about 20-30 years.
In viticultural areas, a warming of 0.1-degC to 1.4degC was likely with stronger westerly winds and lower rainfalls in eastern areas. Most wine-growing areas would experience a drop in rainfall, and by the 2030s there would be 120 more "degree days" - a measure of heat used by growers.
There would be a lot fewer frosts with a longer frost-free season in the South Island and the lower North Island. The annual number of frosts in these areas was likely to drop by 10.
Bud-burst was likely to be between two and eight days earlier, with the time from budburst to harvest dropping so that harvests are as much as 20 days earlier in eastern regions. This compression of the ripening period should be beneficial for ripening and harvest, but Australian studies had shown harvesting in warmer temperatures can also hurt grape quality.
The droughts which happen on average one year in 20 in eastern areas were likely to occur more frequently - every seven to 15 years.
- NZPA
