Thursday, November 15, 2012

Grapevine Development Dates - a sign of climate change?


It is theorized that drier soil and warmer temperatures are causing winegrapes to ripen earlier in Australia. Records of winegrape vintages through time are “an excellent showcase to analyse the fingerprints of climatic changes,” according to a recent paper in Nature Climate Change.

Longview Vineyards in the southern Adelaide Hills wine region.

In the Nature Climate Change article observations of wine-grape maturity and climate trends suggest that warming and declines in soil water content are driving forces behind that maturity, indicated by sugar concentration levels in the grapes.

At a local level we can also find data that supports climate change.

Summary of average dates of phenological growth stages for Willunga Plains 2000-2006



Budburst
30cm shoot
Early Flowering
80% Capfall
Berries Pea Size
Veraison
Cabernet Sauvignon
18-Sep
19-Oct
10-Nov
23-Nov
17-Dec
30-Jan
Chardonnay
3-Sep
11-Oct
1-Nov
13-Nov
6-Dec
18-Jan
Semillon
11-Sep
11-Oct
12-Nov
22-Nov
16-Dec
2-Feb
Sauvignon Blanc
20-Sep
11-Oct
15-Nov
23-Nov
16-Dec
1-Feb
Shiraz
21-Sep
12-Oct
11-Nov
22-Nov
14-Dec
27-Jan


This week CropWatch McLaren Vale records the 2012/13 vintage dates as - 

Vineyards in Willunga are finishing flowering. The most advanced Chardonnay vineyards are at now at 2mm berries (EL-27), Shiraz vineyards are generally at 80% Capfall (EL-25) and Cabernet Sauvignon has progressed ahead to 5% to 50% Capfall (EL-19-23). 

Using these CropWatch observations and comparing to the 2000-06 data it looks as if Vintage 2013 is advanced from those of the first part of the 2000's. It does appear that Vintages from 2006 onwards are getting earlier but is this a definite indication of climate change?

Not definitively.


The Nature paper (1) notes that crop-yield reductions and evolving management practices have probably also contributed to earlier ripening. Also for consideration is the influence of vine age.  As vines mature they tend to have lower crops and ripen earlier. Vineyards in the Willunga Plains where our observations come from were planted in the 1990's - they were still in their adolescence in the year 2000. They are now fully mature. 

Are vines a good indicator for climate change? Yes, scientists consider them to be. Are earlier harvest dates due to climate change? Possibly but vine ages and vineyard management are also having an influence on this.


Whatever happens keep watching your vines. 


(1) Source.



 Title:
Earlier wine-grape ripening driven by climatic warming and drying and management practices
Author:
L. B. Webb, P. H. Whetton, J. Bhend, R. Darbyshire, P. R. Briggs, E. W. R. Barlow
Publication:
Nature Climate Change
Publisher:
Nature Publishing Group
Date:
Feb 26, 2012
Copyright © 2012, Nature Publishing Group

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