On the evening of October 7, 2017, the winds were eerily warm in the San Francisco Bay Area. Strong gusts blew through the region. I felt like something was wrong as I went out for an evening jog. And indeed, overnight, powerlines blew down, sparking wildfires in the hills around the North Bay cities like Santa Rosa. Flames spread rapidly in the high winds and dry vegetation.
Fires have long been a part of the California oak savannah and chaparral. In a Mediterranean climate, vegetation dries out over long hot rain-free summers, ready to burn to control undergrowth and release seeds from fire-adapted plants before winter rains return. Indigenous cultures on the West Coast (and beyond) possess sophisticated fire ecology practices. Historically, tribes worked with regular burn cycles to sustain ecological resources and produce items edible, medicinal, and sacred, practices that continue today where possible.
Even since European colonization and forced removal of Native peoples from their land, fire is no stranger to California. But without regular burning, fuel builds up resulting in more intense blazes that damage ecosystems and human infrastructure and kill people. In the North Bay, suburbanization over the last 2-3 decades has lead people to move deeper in the hills around old agricultural towns of Santa Rosa, Petaluma, and Calistoga. This type of development increases the loss from fires that have historically been a natural part of the ecosystem.
The October fire was special for several reasons. Following a 6-year long drought, heavy winter rains over the 2016-2017 winter led to high vegetation growth rates, so as biomass dried out in the summer, there was a lot of fuel to ready to burn. Also, wind patterns shifted to blow from the east, bringing warm, dry air from the Nevada deserts (known as the Diablo winds), in contrast to the moist, cooler ocean air we usually receive. These factors led fires to catastrophically burn not only hillier areas of the North Bay but also flatland industrial properties and residential neighborhoods very close to city centers. With all this combustion came plumes of thick smoke that limited visibility in the Bay Area, sent air quality indicators into the red, and caused respiratory problems.
The question weighing on many people’s minds was: what is in the smoke? When things burn, carbon dioxide and water vapor are released, but so are many other chemicals, including polycyclic aromatic hydrocarbons (PAHs), metals, and dioxins. Farmers in particular had a lot of questions. The North Bay is an agricultural area, home to Wine Country but also plenty of vegetable crop producers, historic apple orchards, and community and backyard gardens. If their land had burned, could they grow on it? If their produced had not burned, was it contaminated by smoke particles falling from the sky? Did the smoke fallout contaminate their soil? I talked with Vanessa Raditz, a friend who is now using her Master’s in Public Health to organize a community science initiative in pursuit of answers. She said that in the days after the fire, growers really needed information but the information out there was limited, and agricultural extension personnel were at a loss. Working with the Cooperative Extension, she organized volunteers to collect produce samples from farms impacted by the fires, to assess the chemical make-up of the smoke particle fallout and determine if the produce is safe to eat. The results won’t be available in time to help farmers this time around, but will help answer questions for future fires.
Sarick Matzen completed his PhD in Environmental Science, Policy, and Management department at University of California, Berkeley in 2020. He is now a postdoc in the Soil, Water, and Climate Department at the University of Minnesota working on iron cycling in marine systems.