Like cabernet sauvignon? Then grenache just might become your new favorite.
Using climate models and historical records of wine grape ripening patterns, scientists have shown that roughly 50% of the planet’s current wine-growing areas won’t be climatically suitable for their present variety if temperatures increase by 2°C. But if growers opt to plan ahead for climate change and plant later-ripening varieties like grenache now, those losses can be cut in half. In other words, exploiting biological diversity can help vintners buffer against climate change–induced losses, the team concluded.
Ignacio Morales-Castilla, an ecologist at the University of Alcalá in Spain, and his colleagues used wine grapes as an agricultural canary in the coal mine for climate change. Their choice makes sense because wine grapes are extremely sensitive to climatic changes: In one region of France, records stretching back over 600 years have revealed pronounced changes in harvest date in lockstep with atmospheric warming: Since the late 1980s, grapes have tended to be harvested roughly 2 weeks earlier than they had been previously.
The scientists focused their investigation on 11 varieties (cultivars) of wine grapes: cabernet sauvignon, chasselas, chardonnay, grenache, merlot, monastrell, pinot noir, Riesling, sauvignon blanc, Syrah, and ugni blanc. Roughly 1,100 varieties are grown commercially, but these stalwarts make up about a third of wine-growing areas worldwide. (Ask someone to name a wine grape, and they’ll probably land on one of these.)
Climate Models and Historical Records
Morales-Castilla and his collaborators started by using the high-emissions, high-warming scenario climate model known as RCP 8.5 (RCP is Representative Concentration Pathway) to model daily temperatures in roughly 100-square-kilometer pixels over the planet’s surface. They ran 30 simulations, each lasting for 10 years in model time, over three eras: one characterized by no warming (1970–1979) and two characterized by warming of +2°C (2039–2048) and +4°C (2076–2085).
They also used historical records stretching back to the 1950s to catalog when each of the 11 varieties underwent key stages of development (budbreak, flowering, and veraison, the onset of ripening). For each of the three temporal eras the team considered, they then calculated dates of budbreak, flowering, and veraison given the simulated climatic conditions. By comparing the simulated conditions (e.g., maximum and minimum temperature and precipitation) during ripening with the actual ones the grapes experienced historically, Morales-Castilla and his collaborators assessed whether the conditions were conducive to the grapes ripening.
Cultivar Diversity Buffers Big Losses
Over half of current wine-growing areas—56%—wouldn’t support their current cultivar if the Earth warmed by 2°C, the team found. Given a +4°C scenario, that percentage shot to 85%. Vineyards in hotter places like Australia, Italy, and Spain will suffer the largest losses of climatically suitable areas, the team concluded.
However, a bit of foresight could significantly buffer these losses, the researchers showed. If vintners opted to plant later-ripening varieties, only 24% of areas would be unsuitable in a 2°C warmer climate for all of the 11 cultivars the team considered. “Exploiting cultivar diversity more than halved the potential losses with warming,” the team concluded in their paper, which was published last month in Proceedings of the National Academy of Sciences of the United States of America.
We’ll probably be drinking wine made from more later-ripening cultivars in the future, said Morales-Castilla. These cultivars are adapted to warmth because they need more heat to reach optimum sugar and acidity levels. In Burgundy, for instance, varieties like pinot noir might be replaced by grenache, monastrell, or Syrah. (Morales-Castilla is already a fan of monastrell.)
These results are “really significant,” said Mark Howden, an agricultural scientist at Australian National University in Canberra not involved in the research. But switching out grape varieties isn’t the only way to combat the effects of climate change, he said. “There’s also very significant managerial responses that can be taken into account.” For instance, vineyards can be planted in different orientations: In the Northern Hemisphere, grapes grown on south facing slopes are exposed to warmer conditions than those grown on north facing slopes. And pruning can also increase or decrease vines’ exposure to sunshine, said Howden.
A Closer Look
Morales-Castilla and his colleagues are already working on replicating their analysis on a higher-resolution scale. They’re focusing on the Iberian Peninsula (Spain and Portugal). “We’re trying to provide results that can be useful for growers,” said Morales-Castilla.
These results aren’t all gloom and doom, the researchers are quick to point out. “We’re on time to adapt viticulture,” Morales-Castilla said. “But we need to start planning ahead.”
—Katherine Kornei (@KatherineKornei), Freelance Science Journalist