How wildfires creeping toward wine regions in Spain and France may affect this year’s harvest
As wildfires continue to rage across Europe, experts explain how wildfire smoke affects grapes and this year’s batch of wine.
In the wine industry, “guaiacol” might as well be a four-letter word.
This organic compound is one of the main indicators of whether wine grapes and their vines have been impacted by wildfire smoke. The extent of guaiacol on grapes and vines could spell trouble for this year’s crop in Europe as harvesting season approaches.
Wildfires are currently encroaching upon the wine-making regions west of Madrid and Bordeaux. They have burned more than 700,000 acres in Spain and France since the start of the year, according to the European Forest Fire Information System. The spike in fires that started in early July has so far forced the evacuation of more than 300,000 people and continues to threaten the wine crop.
“Exposure to the smoke and heat from the fires, even if it’s farther out, can impact the wine, the output, the product, at the end,” said Faizul Huq, associate teaching professor of Supply Chain & Information Management at Northeastern University, who studies the wine industry. “You may have to dump it all out.”
Some wines are known for their smoky notes, like a syrah. But nobody wants their wine to have “smoke taint,” Huq said, which is the ashy, cigarette taste that compounds like guaiacol can leave behind in a sip of wine.
Even if vineyards are spared the damage directly from the blaze, it’s possible that grapes can be indirectly affected through smoke blown in from a faraway wildfire. Conversely, even if a wildfire is nearby, weather patterns could blow the smoke and spare the vineyards, said Peter Rumble, chief executive officer of the Napa County Farm Bureau.
“It can range from negligible to catastrophic depending on many factors,” Rumble said.
Editor’s Picks
The burning of wood releases what are called volatile phenols, compounds like guaiacol, that are absorbed through the grape’s skin, said Paul Krug, the manager of Domaine de la Commaraine, a wine estate in Pommard, France, which is almost 400 miles northeast of Bordeaux.
“The vine then locks them up with sugars, so the fruit tastes perfectly clean,” Krug told Northeastern Global News. “Fermentation and your own saliva break those bonds back open, which is why smoke taint doesn’t hit the nose but appears afterwards, as an ashtray finish that grows and won’t leave.”
What growth stage the grape is in when it is exposed to smoke is important, Krug added. The grape is particularly vulnerable from véraison, or when the grape starts changing color, until harvest. Growers are nearing that stage now, Krug said.
Wine grape growers protect their crops and infrastructure by setting up strategically placed water tanks and clearing flammable debris. And when managed well, vineyards can be part of the solution to protect against the spread of wildfires, Rumble noted. But the unpredictability of wildfires makes it all the more difficult to prepare for.
There are no horticultural sprays that can protect these grapes from smoke taint, according to the Australian Wine Research Institute. But recent research with the USDA found that a bacteria that naturally occurs on grape leaves could be effective in breaking down guaiacol.
Red wine may have a greater potential for smoke taint because the grapes are processed with the skin intact, where the ashy compounds are stored, whereas white wine grapes are not, according to the Washington State Wine Commission. But it is still possible for wine to be produced in an area where a wildfire has hit, Rumble added.
“There is certainly a point at which smoke taint causes crop loss, but exposure to wildfire and smoke doesn’t necessarily mean a grape harvest is ruined and exceptional wine can’t be produced from that harvest,” he said.
The impact is “dose-dependent,” added Krug.
“But because part of the taint stays bound, a wine can pass every test at bottling and turn ashy two years later in someone’s cellar,” Krug said, noting that some growers in Oregon and California didn’t produce a 2020 vintage after the wildfires that year.
Wine grape growers don’t have to wait until the wine is made to know whether their grapes have been affected. Growers often test their crops before they are harvested. One such lab called ETS Labs based in St. Helena, California, says testing the fruit is the best method to determine smoke taint, because the skins are where the compounds are stored. The lab noted on its website that fruit’s juice and a small batch of wine can also be tested.
Northeastern Global News, in your inbox.
Sign up for NGN’s daily newsletter for news, discovery and analysis from around the world.
“If they were damaged, they would not harvest the grapes at all. They would let them rot on the vines,” Huq said. “It’s too expensive to harvest, macerate the grapes, age the juice, bottle the wine and then find out that the wine tastes ashy.”
In the wine regions near Bordeaux and Madrid, grapes are typically harvested in September, but the process can start as early as August or as late as October, depending on the crop, according to the Bordeaux Wine Council. The farther north, the later the harvest starts.
In some regions, including Burgundy where Krug works, the harvest season has become progressively earlier due to a warming climate. But when it comes to wildfires, grapes won’t be picked to get ahead of any smoke impact, but only when they are ready, Rumble noted.
Grapes are already a very “sensitive and delicate fruit,” Huq said. Aside from wildfires, Europe has seen an extremely hot summer and drought.
As the fires rage on and harvest season approaches, what will become of this 2026 vintage remains to be seen, experts said.
