Abstract Paul PetrieVictor Sadras

Vintage Advancement and Compression in Australia Due to Climate Change

Paul Petrie* and Victor Sadras 
*Australian Wine Research Institute and the South Australian Research and Development Institute, PO Box 197, Glen Osmond, SA 5064, Australia (paul.petrie@awri.com.au)

A shift in phenological development is the most conspicuous biological effect of recent warming, with advanced maturity of grapevines reported in Europe, North America, and Australia. Associated with the advancement in maturity are anecdotal reports of compression of the harvest period, with different varieties grown in the same region now reaching optimal maturity at similar dates and 
a narrower peak period over which a single variety matures. Given the capital-intensive nature of the wine industry (processing capacity is used at most for eight to 12 weeks per year), climatic trends that compress harvests have the potential to affect financial viability. This anecdotal evidence has been difficult to validate and quantify. Analysis of commercial maturity data from 1995 to 2015 suggested that vintage compression was driven by two facets. First, there was consistent reduction in the time interval between maturities of different cultivars grown in the same region. For example, in the McLaren Vale region, the range in dates between peak maturity of Chardonnay and later-maturing Cabernet Sauvignon was ~20 days in the mid 1990s and is now averaging closer to five days. Second, individual cultivars are also reaching maturity over a shorter period within one region. For example, Shiraz across the Barossa region reached maturity over a 30-day period in the mid 1990s and was reduced to a 15-day window by the mid 2010s. While this analysis does not allow separation of the effects of warming and management practices, there have not been step-changes in vineyard management during the study period. Regardless of the causes, the advancement in maturity and reduction in the duration of the window of peak maturity illustrate the challenges faced by wineries to process fruit over a shorter, more-intense period.

Funding Support: Wine Australia and the Australian Department of Agriculture and Water Resources, through the Filling the Research Gap program.