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21 March 2016 16:07

Climate change brings early grape harvests for French wine

Robert McSweeney


Robert McSweeney

21.03.2016 | 4:07pm
Food and farmingClimate change brings early grape harvests for French wine

Increasingly hot summers are pushing wine grapes in French vineyards to mature earlier in the year, a new study says.

As early harvests tend to bring high quality wines, vineyards in France could see some good years in the near future. But it doesn’t bode well for the longer term, the researchers say.

Shifting harvests

France is synonymous with wine. From the sparkling whites of the Champagne region to the deep reds of Burgundy, French wines are some of the most recognisable in the world.

French vineyards are also prolific. In 2013, for example, France produced over five and a half billion bottles of wine, more than any other country.

The study, published in Nature Climate Change, finds that something strange is happening to the harvests of wine grapes across French vineyards – they’re getting earlier.

Using data all the way back to the year 1600, the researchers find that harvests have shifted forward by days or even weeks over the last few decades.

You can see this in the infographic below. Grapes grown in Bordeaux vineyards (green shading) in southwestern France, for example, are ready for harvesting an average of nine days earlier during 1981-2007 than they were for the four hundred years before that.

A little further north, grapes in the Loire valley (yellow shading) are being collected almost 11 days earlier.

Infographic: How is climate change affecting the timing of wine grape harvests in France?

Infographic: How is climate change affecting the timing of wine grape harvests in France? Credit: Rosamund Pearce/Carbon Brief. Data: Cook & Wolkovich (2016).

The biggest change the researchers identify is actually just across the border in Switzerland, where vineyards around Lake Geneva are now harvesting 23 days earlier.

Having analysed data on temperature, rainfall and soil moisture for the region, the researchers suggest this shift to earlier harvests is being driven by rising temperatures as a result of climate change.

A hot year

The best quality French and Swiss wines tend to come in years with high temperatures and early harvests, the researchers say.

In the short term, hotter summers may bring some very good years for these wines, says co-author Dr Elizabeth Wolkovich, assistant professor in organismic and evolutionary biology at the Arnold Arboretum at Harvard University:

So far, a good year is a hot year.

However, this doesn’t mean that increasing temperatures will be good for the wine industry in the long run, the researchers note.

For example, the European summer heatwave in 2003 set a new record for an early harvest, with grapes maturing an entire month earlier than average. But the heat stress on vineyards saw European wine production drop to a 10-year low. Nor were the wines that year of a particularly high quality, the researchers add.

Wine grapes tend to be quite fussy about the climate in which they can be grown. Further warming could see some regions become unsuitable for the grape varieties they’re renowned for, says Wolkovich:

If we keep pushing the heat up, vineyards can’t maintain that forever.

For example, a study from 2011 found that climate change could make much of the Burgundy region unsuitable for growing pinot noir, while other research suggests Bordeaux could become too warm for its merlot grapes.

‘Fundamentally altered’

It’s not just that harvests are shifting earlier, the researchers say. The relationship between the weather and how grapes grow has been “fundamentally altered”.

Usually, a dry end to the summer allows temperatures to climb high enough for grapes to mature. A rainy period can delay the harvest by taking the edge off the heat.

But in recent decades, the temperatures are climbing so high that grapes mature even if conditions are wet, the new study finds.

This means the link between dry conditions and the grape harvest has “decoupled,” says lead author Dr Benjamin Cook, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. He tells Carbon Brief:

Thanks to global warming, drought is no longer a prerequisite for early harvests.

As temperatures are expected to rise further in the coming decades, understanding how the relationship between climate and grapes is changing may prove critical for wine producers in France and Switzerland, Cook says.

Main image: Red grapes in the vineyard. © sarra22/Shutterstock.

Cook, B I. and Wolkovich, E. M. (2016) Climate change decouples drought from early wine grape harvests in France, Nature Climate Change, doi:10.1038/nclimate2960.

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