In a recent post, I discussed where various wine-grape varieties are currently grown. I noted that there is more difference between countries than similarity. This is a Good Thing in the face of global climate change, as it means that grape varietal diversity is not under immediate threat.
However, it has been noted that the vineyards of the world are changing, with some varieties becoming dominant in many regions around the world. These include the obvious international candidates, such as Cabernet Sauvignon, Chardonnay and Pinot Noir. This is probably a Bad Thing, both biologically (less diversity) and economically (more competition for the same markets).
So, it is worth having a look at some relevant data. Recently, Kym Anderson & Signe Nelgen published a report on Australia’s Declining Winegrape Varietal Distinctiveness; so, Australia seems like a good place to start, as an example of varietal changes in a New World viticultural region.
The information for this post comes from the Global megafile, National 0920 spreadsheet file of:
Anderson, K. and S. Nelgen (2020) Which Winegrape Varieties are Grown Where? A Global Empirical Picture (revised edition). University of Adelaide Press: Adelaide.The data consist of the estimated growing areas for each of 139 grape varieties, for each decade from 1960 to 2016. Sadly, the data for 1980 are seriously incomplete, as this includes only 20 varieties (compared with 41 in 1970 and 40 in 1990, for example). Since the missing varieties include obvious things like Cabernet Franc, Côt (aka Malbec), and Pinot Noir, I have left this year out of most of my analysis.
First, it is important to note that there was a rapid increase in Australia’s wine-grape bearing area between 1990 and 2000, associated with a boom in premium (bottled) wines, as shown in the next graph. It is interesting to see whether there was also a change in varietal mix during this time, or whether the same dominant varieties simply increased in area.
As in my previous post on grape varieties, I have used a network as a convenient pictorial summary of the complex varietal data. As before, I first calculated the percent of each grape variety as a component of the viticultural area, and then calculated the similarity among pairs of years using the Bray-Curtis measure (important, because it ignores varieties that do not occur in either of the two years being compared). I then used these similarities to calculate a NeighborNet network, as shown next. Years that are closely connected in the network (along the edges) are more similar to each other, in terms of their grape varietal composition, than they are to years further apart.
Well, the basic picture is pretty clear. There has been a continual change in the varietal make-up of Australia's vineyards from 1960 (at the top of the graph) until recently (2016, at the bottom). The years are, indeed, somewhat different from each other, especially 1960, but their similarities to the general pattern outweigh their differences. The 1960 sample is different because, at that time, Australia’s vineyards were often planted to high-yielding multi-purpose varieties, and wine-making was concentrated on what were then known as "sherry" styles.
The network shows that there were large changes in composition between 1970 and 1990, and also between 1990 and 2000, and apparently in the same direction. There were no differences in the number of reported varieties (1970: 42 varieties; 1990: 40 varieties; 2000: 43 varieties), but clearly the relative abundance of these varieties changed considerably. Anderson and Nelgen (cited above) note that these changes were associated with increasing dominance of the most popular grape varieties. They illustrate this using the following graph of the most abundant varieties, which shows that the area of the main international varieties increased disproportionately.
This pattern was a general one, as there was an overall decrease in varietal diversity after 1990. I calculated Simpson's Diversity Index for each year, which is a formal measure of such things. Since there was little change in the number of reported varieties through time, in this case the index will be measuring how equal were the relative grape areas — low index values indicate very uneven abundances (alternatively, index = 1 would mean that all varieties had the same growing area). The next graph shows that the index consistently decreased between 1990 and 2010, suggesting it wasn't just the main varieties involved in the change during the boom.
Notably, there was very little change in the area of the major varieties between those years, but many more grape varieties are now being recorded. For example, only 40 varieties have data for 2010 but there were 118 recorded for 2016. There is the possibility that much of this difference is simply due to more thorough data collection. However, there has also been a deliberate response to climate change, as many vignerons start to trial new varieties from (especially) dry climates around the world. These varieties are often in low abundance at the moment (eg. there are 35 varieties listed as 1–2 hectares), and it is often smaller wineries that are most interested in them, but the area will presumably expand if the trials are successful.
Next time, I will look at France and Germany, as examples of Old World viticultural changes.
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