Many of the world’s most revered vineyards may face the choice of diversifying the grape varieties they grow or risk harvesting smaller and smaller crops, as climate change brings less favourable conditions.

Even if the world manage to rein in the greenhouse gas emissions causing average global temperatures to rise as the Paris agreement outlines – limiting global warming to 2C – then the regions of the world suitable for growing wine grapes could shrink by as much as 56 per cent.

Currently humanity is not on course to meet that target. Emissions over 2019 were 4 per cent higher than when the Paris agreement was signed in 2015, and the United Nations has warned that current trends put the planet on course for a 3.4C temperature rise over the next 80 years.

A new study warns that under a potential scenario of 4C of warming, 85 per cent of lands suitable for vineyards would no longer be able to produce good wines because the grapes are extremely sensitive to the changes in temperature and season brought by climate change.

“In some ways, wine is like the canary in the coal mine for climate change impacts on agriculture, because these grapes are so climate-sensitive,” said Benjamin Cook from Columbia University and the Nasa Goddard Institute for Space Studies, co-author of the study.

But all hope is not yet lost. 

“There are still opportunities to adapt viticulture to a warmer world,” said Professor Cook. “It just requires taking the problem of climate change seriously.”

The study suggests wine producers could look at diversifying their crop by “reshuffling” grape varieties. Such a move could halve the potential losses of wine-growing regions under 2C of warming, the authors say.

The team suggests crop diversity could be key to making agriculture more resilient to climate change, and said wine grapes offer a unique opportunity to test this assumption. 

Wine grapes are both extremely diverse – there are more than 1,100 different varieties planted today, growing under a wide range of conditions – and they are well-documented, with harvest data stretching back centuries. 

The researchers – led by Ignacio Morales-Castilla at the University of Alcalá in Spain and Elizabeth Wolkovich at the University of British Columbia, Vancouver – focused on 11 varieties of grape: Cabernet Sauvignon, Chasselas, Chardonnay, Grenache, Merlot, Monastrell (also known as Mourvedre), Pinot Noir, Riesling, Sauvignon Blanc, Syrah and Ugni Blanc.

For the 11 varieties, the team used vintner and researcher archives to build a model for when each would bud, flower, and ripen in winegrowing regions around the world under three different warming scenarios: 0, 2, and 4C of warming. Then they used climate change projections to examine which regions those varieties would still be viable in the future.

Losses were unavoidable under both warming scenarios, due to shifting temperatures and seasonal changes which would affect conditions while the varieties were ripening. These factors would considerably impact the wines’ quality. But the team found that “by switching these varieties around, you can reduce losses by a significant amount”, said Professor Cook.

With 2C of global warming and no attempts at adaptation, 56 per cent of the world’s wine-growing areas may no longer be suitable for growing wine. But if wine producers switch to varieties more suitable for the changing climate, only 24 per cent would be lost. 

For example, in France’s Burgundy region, the authors suggest heat-loving Mourvedre and Grenache could replace current varieties such as Pinot Noir. In Bordeaux, Cabernet Sauvignon and Merlot could also be replaced with Mourvedre.

Implementing such major cultural changes in areas steeped in rich viticulture history would be a significant challenge, as would the legal position – strict rules govern the grapes used in wines sold as coming from particular regions.

However, some change is already afoot. For example, in Bordeaux, where Cabernet Sauvignon dominates blends, just a handful of grapes including Cabernet Franc, Merlot, Petit Verdot and Malbec were previously permitted to be used. 

But this changed in July 2019. Bordeaux wineries reportedly authorised the use of four new red grapes to combat temperature increases in Bordeaux. They are: Marselan, Touriga Nacional, Castets, and Arinarnoa.

“Conversations in Europe have already begun about new legislation to make it easier for major regions to change the varieties they grow,” said Dr Wolkovich. 

“But growers still must learn to grow these new varieties. That’s a big hurdle in some regions that have grown the same varieties for hundreds and hundreds of years, and they need consumers who are willing to accept different varieties from their favourite regions.”

The scientists said cooler wine-growing regions such as Germany, New Zealand and the US Pacific Northwest would be relatively unscathed under the 2C scenario. These areas could become suitable for warmer varieties like Merlot and Grenache, while varieties that prefer cooler temperatures, such as Pinot Noir, could expand northward into regions not currently suitable for growing wine.

Wine-growing regions that are already hot now – such as Italy, Spain, and Australia – faced the largest losses, because they are already limited to planting the warmest varieties.

The variety-swapping was less effective at higher amounts of global warming. With 4C of warming, planting climate-specific varieties reduced losses from 85 to 58 per cent – about a third.

The researchers note that management practices like increased irrigation and using shade cloths can also help to protect grapevines, but only at lower levels of warming.

Ultimately, the effectiveness of any strategy depends on growers having the options and resources to adapt at a local scale, and on reducing greenhouse gas emissions and limiting warming globally, the authors said.

The research is published in the ​Proceedings of the National Academy of Sciences.

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