Adapting America’s Favorite Red Wine to Climate Change: Challenges and Solutions
Late-summer heat waves are posing a threat to Napa Valley’s iconic cabernet grapes, which are responsible for producing some of the most expensive wines in the United States. As temperatures continue to rise due to climate change, winemakers are coming to terms with the fact that they will need to adapt in order to survive in a hotter climate.
In California’s Napa Valley, cabernet sauvignon reigns supreme. This bold red wine has garnered global recognition, with some bottles fetching prices in the hundreds of dollars. However, the increasingly severe heat waves are proving to be detrimental to the grape variety, particularly during the ripening phase in late summer. With temperatures on the rise, the wine industry is slowly realizing that Napa may no longer be the premier cabernet region it once was.
Facing the challenges brought about by climate change, wineries across the world are embracing innovation. New technology is being implemented to keep the grapes cool during periods of intense heat. Some wineries are taking it a step further by exploring the cultivation of new grape varieties, even going as far as uprooting valuable cabernet vines to make room for grapes from warmer climates. The objective is to discover heat-tolerant grapes that complement cabernet, potentially compensating for the flavors that cabernet may lack as temperatures soar. While many bottles labeled as cabernet already contain small amounts of other grape varieties, winemakers may require greater flexibility in the future.
“We know we have to adapt,” shares Avery Heelan, a winemaker at Larkmead Vineyards in Calistoga, Calif. “We can’t afford to ignore the changes, because each year, the conditions are becoming increasingly extreme.” However, blending cabernet with other grapes comes with its own set of risks. In order for a wine to be labeled as cabernet in the U.S., it must consist of 75% cabernet grapes or more. Any less, and it is classified as a red blend. Generally, blends do not command the same prices on store shelves as cabernet, especially since consumers are accustomed to selecting U.S. wines based on the grape variety. Transitioning away from cabernet would represent a significant financial gamble for Napa’s multibillion-dollar wine industry.
Elisabeth Forrestel, an assistant professor of viticulture and enology at the University of California, Davis, remarks, “It is a significant shift. Without changes in the market or consumer demands, it is challenging to convince someone to grow something that does not sell or fetch the same price.”
Some of the grapes growing at Larkmead Vineyards are not familiar to many American wine enthusiasts. Rows of vines are labeled with names such as touriga nacional, aglianico, charbono, and tempranillo. “There’s not a huge market for many of these varieties,” explains Heelan as she walks among the vines on a scorching summer afternoon. “We selected them not for their popularity, but for their unique qualities.” Established over a century ago, the winery is renowned for its cabernet sauvignon. These lesser-known grapes were planted only a few years ago as part of a research vineyard that replaced cabernet vines. “Most people would probably consider it a bit crazy, considering it’s 3 acres of perfect cabernet land,” notes Heelan. “But given the climate and how drastically it has changed over the past decade, we really need to start adapting.”
Located in the warmer northern end of Napa Valley, the vineyard has recently experienced extreme heat, serving as a wakeup call for Heelan. During a late-summer heat wave in 2022, temperatures at the vineyard reached just under 120 degrees. “When it gets that hot, the vines essentially shut down,” she explains. “They become dormant, which means they stop ripening.” In extreme heat, cabernet grapes can lose their vibrant color and dehydrate, resembling raisins, resulting in wines that are sweeter and higher in alcohol content. Heelan suggests that the grapes being tested at the vineyard could offer added color or acidity to cabernet, helping to balance out the wine when temperatures have a negative impact.
Despite the potential benefits, the experiment comes at a cost. In addition to the revenue loss from removing cabernet, grapevines take up to five years to yield their first crop, with several more years needed for the wines to mature. Only then will they be able to assess the performance of the new grapes. However, the goal is to equip the winery for the future, knowing that temperatures are likely to rise further. “The more we experiment and learn how to adapt, the better the wines become,” Heelan affirms.
Further south, Shafer Vineyards is situated in the heart of Stags Leap, a Napa wine region renowned for its high-end cabernets. Winemaker Elias Fernandez highlights the benefit of a cool evening breeze blowing in from San Francisco Bay that enhances the grapes. This summer, heat has already posed challenges, with July marking the hottest July on record in California. Fernandez points to a grape cluster where small green grapes are interspersed among larger purple ones. “This is the impact of the heat,” he notes. “The fruit isn’t ripening, so this is where we lose some of our crop.”
While the damage is not as widespread this year compared to 2022, Fernandez acknowledges that the winery is exploring technology to aid the cabernet vines. They are currently installing misters that spray water into the air to lower the temperature. “It’s a continuous mist,” he explains. “Have you ever been to a party with misters? Doesn’t it feel good? Well, that’s what the vines experience.” However, utilizing additional water presents a challenge in drought-prone California. Moreover, the water droplets can intensify the light on the grapes and cause them to burn, requiring the misters to operate until sunset to prevent the accumulation of droplets. Fernandez is optimistic that the misting system will help the cabernet vines maintain their productivity at the highest level.
“I believe our first step should be mitigation, aiming to preserve the true essence of Napa Valley’s varietal,” he states. “Our objective is to buy time and observe how this situation evolves.” At present, he is not contemplating planting other grape varieties. With wines priced at $100 and above, cabernet is central to their business. “It’s difficult for me to imagine people abandoning cabernet and switching to something else,” Fernandez admits. “I truly believe it is the king of wines worldwide.”
Elisabeth Forrestel is among the individuals striving to comprehend the significant temperature fluctuations. In her laboratory at UC Davis, her research team is crushing Napa Valley grapes inside plastic bags for analysis at the molecular level to monitor their changes throughout the summer. Forrestel’s lab is collecting wine grapes from Napa Valley at various stages of the growing season, along with detailed temperature data, to determine how heat affects the key compounds responsible for wine quality. Studies indicate that the average temperature during the final 45 days of the growing season in Napa, when grapes ripen, has increased by nearly 3 degrees Fahrenheit from 1958 to 2016. However, it is the extreme heat waves that have the most significant impact on the molecules that contribute to a wine’s color and aroma.
“When there are extreme heat events, it can greatly affect the development of the flavor profile,” Forrestel explains. “If it were just an average change, it would be easier to manage.” Forrestel is working on updating the Winkler Index, a central guide for winemaking established in the 1940s. The index indicates the ideal locations for cultivating different wine grape varieties based on the level of heat they receive. Initially indexed for cabernet sauvignon, Napa Valley’s classification could shift as temperatures continue to rise.
Forrestel notes that cabernet, being the most widely grown wine grape globally, is adaptable to varying temperatures. The question remains whether Napa winemakers will need to adopt new strategies to sustain its high-quality production. Since grapevines can endure for 50 years or more, winemakers must make planting decisions today that can withstand a warmer future. “Certain paradigms regarding what to plant need to change,” she emphasizes. “People must adopt different approaches to enhance resilience and provide more options.”
Blending cabernet with other red grapes emerges as a potential strategy. However, U.S. regulations stipulate that any bottle labeled as cabernet must contain at least 75% cabernet. Consequently, wineries may eventually need to consider relabeling their wines as “red blends.” “There is a perception that blends are of lower quality than high-quality cabernet, and they are not priced at the same level, so this represents a significant shift,” Forrestel comments. This challenge is unique to U.S. winemakers, as many other countries label their wines based on region rather than grape. The renowned red wines from Bordeaux in France already consist of a blend of six grapes, including cabernet, affording winemakers greater flexibility. In response to heat-related challenges, French authorities recently authorized the blending of four additional red grape varieties. Since these wines are labeled as Bordeaux, consumers may not even notice the change.
In the U.S., wines are typically labeled based on grape variety, a system that was encouraged when the domestic wine industry was gaining prominence decades ago. The aim was to compete with European wines by simplifying the selection process for consumers and showcasing the quality of American wines. However, this system may now pose challenges. Cabernet sauvignon is the most popular red wine in the U.S., according to NielsenIQ. Forrestel suggests that consumers also play a role in addressing the issue by creating demand for wines better suited to a warmer climate. “Remain open,” she advises. “It is easy to stick to what you know when making a purchase. Trust your preferences rather than conforming to what you are told to like.”
In conclusion, the wine industry is at a crossroads as it grapples with the impacts of climate change on grape cultivation and wine production. Winemakers in regions like Napa Valley are being forced to adapt to rising temperatures and more frequent heat waves. The challenges posed by climate change are prompting innovation, experimentation, and a reevaluation of traditional winemaking practices. As wineries explore new grape varieties, implement advanced technologies, and consider blending strategies, the future of iconic wines like cabernet sauvignon hangs in the balance. By embracing change, investing in research, and engaging consumers, the wine industry can navigate the challenges of climate change and ensure the continued production of high-quality wines for generations to come.
