Napa Valley Prepares for Wildfire
Wildfire has become an all to frequent threat to Napa Valley’s vineyards. Stoked by high winds and low humidity the deadly Atlas Fire (2017) burned over 51,00 acres and destroyed or damaged six wineries. Last year, during California’s worst wildfire season to date, the Glass Fire (2020) burned 67,000 acres. It destroyed hundreds of homes and commercial buildings, including the historic Chateau Boswell Winery. With a drought emergency now declared across much of the state, there is growing concern for the 2021 fire season.
Globally, many wine regions face an increased wildfire risk. Dozens of wildfires impacted Portugal and Spain in 2017. Last year Australia saw an intense ‘bushfire’ season; the Cudlee Creek fire in South Australia affecting 60 grape growers in the Adelaide Hills wine region. With warmer, drier conditions and increased drought associated with climate change, vineyard owners and communities are seeking ways to mitigate the risks to life, vineyards and their region’s tourism economies.
Napa County Prepares
On April 7, 2021 the Napa County Board of Supervisors approved $6.4 million to fund the first year of fire protection projects recommended in their Community Wildfire Protection Plan. A collaborative effort led by the Napa Communities Firewise Foundation, at a cost of $42 over 5 years, the plan hopes to both prevent wildfires and reduce their impact should they occur. Work is already underway on fuel reduction projects throughout the county.
In Napa County, 75% of the land is considered to be a high hazard fire environment. Years of drought and the delayed onset of the rainy season, which starts nearly a month later than it did in the1960s, contribute to the accumulation of dried vegetation. With the shift in rainfall patterns, fire season now overlaps with the critical harvest period.
The plan includes measures such as fire breaks and better evacuation route planning. The creation of ‘defensible spaces’, or buffers, to keep fires from reaching homes or other structures are a key element of the plan. Around homes and vineyards dried vegetation and underbrush should be cleared and tree branches cut back beyond the reach of a potential underbrush fire. Grass should be kept clipped short, so it does not become a fuel source; this is particularly important in organic vineyards with cover crops between rows. A final element is the ‘hardening’ of structures through the use of fire-resistant building materials.
Smoke in the Vineyard
Beyond the danger of fire, smoke poses a great economic threat to the wine industry. When grapevines are exposed, the fruit and leaves can absorb smoke compounds, creating an unpleasant taste of smoke and ash or ‘taint’.
Despite the devastating impact, the study of smoke taint is relatively new. Scientists are still working to identify the exact pathway by which ‘smoke taint marker compounds’ enter the berries and which compounds are most important. No common industry scale yet exists to quantify smoke taint though the Australian Wine Research Institute is working to create one.
Grapes can be negatively impacted with as little as 30 minutes of exposure to smoke, though varietal and timing of the exposure in the growth cycle are also important factors. Once exposed, the available mitigation options are few and are often not very successful.
Limiting the amount of skin contact through cold or shorter macerations (the process of extracting color, tannins and flavors from the skins) may reduce the intensity of the smoke flavor. The addition of wood chips can potentially mask the taint, though the resulting wine may not be representative of the wine maker’s usual style.
Researchers are experimenting with methods, including reserve osmosis, the use of fining agents such as activated carbon, and the addition of enzymes or polymers in order to remove, dissolve or treat the taint associated compounds. But these methods can also remove compounds that impart desirable flavor elements to the wine. Finally, tainted wine can be blended with untainted, with success often dependent on the severity of the taint.
The best option, of course, is to reduce the risk of wildfires as much as possible and avoid smoke exposure altogether.
Information on smoke taint comes from the following article, link can be found at our research tab: Mirabelli-Montan YA, Marangon M, Graça A, Mayr Marangon CM, Wilkinson KL. Techniques for Mitigating the Effects of Smoke Taint While Maintaining Quality in Wine Production: A Review. Molecules. 2021 Mar 17;26(6):1672.