- Author: Jeannette E. Warnert
A summer of smoke and ash in many parts of California has raised questions about the safety of produce growing on farms and in the garden, eggs laid by chickens who peck around in ash-laden areas, and remediation needed to safely and effectively grow food in the future.
UC Agriculture and Natural Resources brought together experts who have researched the effects of previous fires' fallout and studied soil contaminants to share their insight in a two-hour webinar now available at Post-fire Soil Safety video.
“The No. 1 health concern during a fire is smoke inhalation, and it's been well documented that wildfire smoke can negatively impact both the heart and the lungs,” said Claire O'Brien, a pharmacology and toxicology doctoral student at UC Davis. “However, the chemicals found in the smoke don't just stay in the air. They can deposit onto plants and into soil and water.”
Although every fire is unique, some generalizations can be drawn from research conducted following previous fires. UC Cooperative Extension food systems advisor Julia Van Soelen Kim detailed a study conducted following the October 2017 wildfires in Sonoma County and across the North Bay.
With the help of UC Master Gardener and community volunteers, the researchers collected over 200 samples of homegrown collard greens, lettuces, kale and chard that were exposed to wildfire smoke and ash. A subset of the samples were analyzed by a private laboratory.
“There was very low concern about chemicals on produce,” Van Soelen Kim said. “No samples had detectable levels of lead, arsenic, mercury or chromium. And that's a huge sigh of relief.” However, analytical results vary by site, site history and by fire event, and few have pre-fire baseline data to compare with.
Van Soelen Kim said basic food-safety practices should be followed when preparing to eat food grown in a home garden, regardless of ash or smoke contamination.
“You should always wash your hands before and after harvesting, and wash your produce in running water to mitigate any kind of potential risk,” she said.
Are backyard chicken eggs safe to eat?
Another study outlined at the webinar used a similar process to determine whether there might be contaminants in the eggs laid by backyard poultry that live and feed in areas exposed to wildfire ash and smoke.
Scientists know from previous research that chickens exposed to lead in their environment can produce eggs with high lead content and that heavy metal content of ash from urban wildfires is higher than from rural wildfire.
“We combined those two pieces of research with what we know that chickens do all day: they peck at the ground for hours on end,” said Todd Kelman, a veterinarian in the School of Veterinary Medicine at UC Davis. “That makes for a pretty good hypothesis that urban wildfire could pose a risk for the production of eggs and poultry that contain heavy metals.”
Kelman and his team put out a call for eggs from backyard poultry and received samples from 344 premises in fire-affected and non-fire-affected areas of California.
Surprisingly, egg samples that contained higher lead levels came from parts of the state that were not directly impacted by ash and smoke.
“Did our data support our hypothesis that proximity to urban wildfire is a driving source for lead in eggs of backyard poultry? The answer is not so much,” Kelman said. “So, is it safe to eat eggs from your backyard poultry? We can't give you a definitive answer to that question. But we do suggest you assess your risk and reduce the risk of contamination.”
Practices that reduce the risk include keeping chickens off the ground, using a chicken feeder that prevents spillage onto the ground and making calcium readily available, for example in the form of oyster shells, because calcium can prevent the absorption of lead. Making sure that chickens are provided uncontaminated water is also an important part of risk reduction.
For confirmation on the safety backyard chickens and their eggs, lab tests for eggs are available for $60 from the California Animal Health and Food Safety Laboratory at UC Davis, or chickens may be submitted to CAHFS for necropsy.
Are soils safe for growing food after a fire?
Fire effects on soil is another consideration in burned areas, said UC Cooperative Extension urban agriculture advisor Rob Bennaton.
“Fires heat topsoil layers. They reduce the amount of living micro-organisms at the site of the burn, and also affect organic matter and nutrients. Ash deposits over time may make soils more alkaline,” he said. “As a result of these combined factors, there are temporary changes in nutrient levels and the capacity for soils to exchange nutrients for optimal plant growth and nutrition.”
With proper land care and management, soils can be remediated over time.
“It won't happen overnight. Soils were developed over millions of years,” he said.
Some ways to improve safety when gardening in fire-affected areas including keeping the soil covered with wood chips or other landscape mulch to reduce airborne soil dust. Use drip irrigation to prevent up splash onto the undersides of growing vegetables. Promote good drainage, especially at the bottom of slopes to prevent the concentration of contaminants.
Lab tests are often needed to determine the soils' post-fire characteristics. “Don't guess, but test,” Bennaton said.
The UC Master Gardener Program can provide technical assistance to help home gardeners find resources for home soil testing, he said.
Resources and information shared during the webinar
Post-fire soil resources and soil testing information
- UCCE publication on Soils in Urban Agriculture with soil testing & sampling information
- The UC ANR Healthy Soils Website, which has many resources worth reviewing.
- Tips for Interpreting Soil Analysis
- UC Master Gardener of Sonoma County 2018 workshop video “Effects of fire on soil”
Post-fire food safety
- Research on produce safety and backyard chicken egg safety after the 2017 wildfires in California is available at Produce Safety after Urban Wildfire. To view a past webinar recording with these research findings, visit Post-fire Food Safety.
- Poultry wildfire resources from the UC Davis School of Veterinary Medicine
- UC Davis School of Veterinary Medicine: "Safety of Backyard Chicken Eggs Post Wildfire" video
- Best Practices for Produce Safety After Fire
- Understanding Risk: A community guide for assessing the potential health impacts of locally grown produce exposed to urban wildfire smoke
Firewise and sustainable home landscaping design in the defensible space zone
- Visit the UC Master Gardener Program of Sonoma County firewise landscaping web page.
- For a recent firewise & sustainable design and maintenance video by the Resilient Landscapes Coalition.
Impact of smoke & ash on plants
- Author: Mimi M Enright
The UC Master Gardener Program of Sonoma County (MGSC) Garden Sense program via its sponsoring organization, Sonoma Water, was named the recipient of the Smart Water Application Technologies (SWAT) Outstanding Public Engagement Award on October 29, 2020.This award recognizes a water provider with a successful program focused on public engagement and education on smart, efficient irrigation technologies and practices.
The Garden Sense program, initiated in September 2013, is available free of cost to any Sonoma County resident. MGSC presently has 46 trained volunteer Garden Sense consultants who meet with residents in their gardens to evaluate their existing landscaping and irrigation practices, and advise them on how to increase their irrigation efficiency, reduce or remove their lawns, and create climate-appropriate gardens based on their functional needs. Over 900 client consultations have been conducted since the program inception.
Clients who have received a Garden Sense visit are surveyed and asked to rate how helpful the program has been in helping them complete their lawn removal project and/or change their home irrigation practices. The majority of respondents indicated that the visit was either ‘Very helpful' or that they ‘Could not have done it without them'. Conservative estimates of water savings as a result of Garden Sense consultations are equivalent to 26 million gallons of water over the life of the program! One of our clients who was new to the Sonoma County area stated:
“We couldn't have done it without them . . . their advice and expertise was essential to our successfully creating a low water-use landscape. Thank you so much!”
Visit Garden Sense for more information
about the program, or to request a visit.
Here is a summary of some of the work our office is doing during shelter in place.
Fire & Resiliency
UCCE Sonoma is building on the foundational work of other county departments such as Sonoma Water and Permit Sonoma, by providing outreach to private landowners to address forest health, vegetation management and fire fuel reduction.
Lake Sonoma Decision Support System: Development of an online geo spatial reporting tool to help landowners assess:
Match.Graze: development of an online database that connects land owners and grazers.
- Filmed educational videos
- Creating website
- Current status: roll out in early June.
Good Fire Alliance: partnership with Audubon Canyon Ranch to assist landowners in managing fire fuels through prescribed burning on private and publicly owned lands. The following prescribed fires are in the active planning stage:
- 100+ acre burn unit at Cooley Ranch near Lake Sonoma; late May.
- Sonoma Ecology Center is planning a burn at Van Hoosear Wildflower Preserve; late May - early June.
- Bodega Pastures spanning several weekends in October/November.
Resilient Landscapes: Master Gardener collaborative project to:
- Host Firewise webinars
- Develop materials for Fire Safe Sonoma's Living with Fire brochure and webpage resource.
- Post Fire Survival/Mortality: research project to develop a quick and simple post-fire tree survival reference tool to aid with triage of burned landscapes.
- Working with local fire departments to homogenize fire-resilient landscape standards.
Oak Tree Health: organized, hosted and presented:
- California Oak Workshop with science based oak health information. Over 500 participants.
- Sudden Oak Death Blitz pivoted to online, educating and distributing 93 test kits to the public.
Food Systems & Security
- “Stay Home Grow Food” series has reached over 350 people with videos plus resources via an extensive social media campaign.
- Gardener Sense program delivered by video conference to help homeowners reduce water use.
- Master Gardener's are pivoting their classes to webinars.
The value of a strong, connected local food system to sustain the resiliency of our communities has never been more clear.
Coordinating with Sonoma County Food System Alliance and strategizing for a series of video conferences on longer term emergency food response planning & strengthening the local food supply chain looking to local production & distribution as part of meeting food need.
- Meeting on March 23 with over 50 emergency food responders to strategize on coronavirus response.
- Chairing the Community Organizations Active in Disaster (COAD) Food group. Continue to collaborate with the group to meet the needs of emergency food organizations.
- Sonoma County Food Recovery Coalition
UCCE used connections to secure donations of over 12,000 wine boxes to
Redwood Empire Food Bank for boxing and distributing food.
Local Meat Supplies: Mobile Slaughter Unit (MSU)
UCCE is working with local livestock producers in Marin/Sonoma to create a business plan for an MSU which can assist local livestock producers with a local, safe option for processing livestock.
- Applying for USDA grant to assist these producers to determine the functionality of keeping it in production.
- Will develop educational and management strategies to ensure economic security for small-scale livestock producers.
Integrated Pest Management
- Collaborating with UC Davis researchers to continue projects that address soil and fungal pests that shorten the lifespan of vineyards.
Critical research on the newly detected invasive Mediterranean oak borer (pictured) found in valley oak in eastern Sonoma County. Collaborators include Cal Fire, US Forest Service, and CDFA.
4-H youth educational programs have continued to engage youth and adults with online technologies.
- Developed fact sheets to support volunteer educators in delivering online programs available at Youth Development Resources
- Short-term educational programs have been implemented reaching elementary-aged children with science and art content.
- Ongoing programming has been transitioning online focused for teens around college and career readiness (Juntos 4-H) and youth participatory action research.
Annual Sonoma 4-H Open House and ChickenQue transitioned from a full-day chicken BBQ lunch fundraiser to a radiothon.
- Partnered with local radio The Bull 93.7 to do a radiothon.
- The station promoted 4-H with interviews of staff, volunteers, and youth.
- The event also served as a public awareness campaign showcasing the program's legacy helping youth reach their full potential.
Working with local dairy and livestock producers to apply for grants from CDFA to reduce greenhouse gases:
- Alternative Manure Management Program
- Healthy Solis Program
If funded, these grants would bring over $5 million to reduce GHG by 4,154 MTeCO2
Support Local Producers
- Working with local creameries and FEED Sonoma, to develop a dairy CSA box option.
- Revisit the County Lands for Food Production program initiated by UCCE to increase the availability of county owned land to communities, farmers and ranchers.
- Find Local Food & Aid the Community
Providing information and updates.
Coronavirus Resources webpages provides information for agricultural enterprises focusing on financial resources, Ag worker safety and food safety and includes resources for where to find food from local farms and for opportunities to volunteer.
Sonoma county residents love their oak trees, and with good reason: Oak woodlands are a source of immense value not just to the more than 330 types of animals and hundreds of other organisms they support, but also to the cultural, economic, and social fabric of our society. Sudden oak death (SOD) threatens to unhinge these systems, imperil biodiversity, create hazard trees or fuel for fires, and potentially infect agriculturally or horticulturally important plants. So whether it means adapting educational events to virtual spaces, delivering materials by mail, training online, answering home phones instead of staffing the Master Gardener desk, or collecting leaves for the SOD blitz by bicycle while wearing a mask and social distancing, the UCCE Sonoma SOD Program is not letting COVID-19 slow us down.
A key endeavor of this group is the yearly Sudden Oak Death Blitz in partnership with UC Berkeley's Forest Pathology and Mycology Lab. This state-wide citizen science project allows landowners to receive free testing of California bay laurel and tanoak leaves, contribute to long-term scientific research, and update the SOD Map Mobile app used by landowners and professionals to assess disease risk in their area. As SOD Blitz creator Dr. Matteo Garbelotto wrote in a letter addressed to all Californians about this year's program,
“The SOD Blitzes have become a tradition for many, while providing key information to help us save our oaks from a devastating disease.”
UCCE Sonoma hosts six blitz events annually whereas most counties hold just one, and we were eager to test new areas of tree mortality that were discovered after last-year's blitz had already passed. Here's how we made it work:
- Training took place online.
- Three Zoom sessions were set up with SOD team members for participant questions.
- Collection packets were mailed to most participants, and the rest picked up following strict safety guidelines supervised by staff.
- Leaves were collected at homes and on public land by walkers, cyclists, and others engaging in outdoor exercise.
- Kashia Pomo staff continued to sample on their land.
- In collaboration with SSU's Center for Environmental Inquiry, we hosted the only SOD blitz in the state that was fully bilingual in Spanish and English.
Despite limitations posed by COVID-19 regarding how to train volunteers, access areas where leaves could be sampled, and safely pass materials and samples between participants and blitz organizers, this year's campaign is on track to be even more successful than 2019. Returning leaves by mail instead of in-person allowed residents on the coast and other remote areas to participate easily, leading to a better geographic distribution of sampling. Online trainings and Q&A sessions, though less personal and lacking physical demonstrations, encouraged people with schedule constraints to give the blitz a try. One participant with extra time on his hands reported that he thought this was a great way to give back to the community in a time of need. Based on the number of participants and collection packets requested, we estimate a 15% increase in sampling from last year, including all major areas of Sonoma county and most of Mendocino county.
And things are just getting started. Though a SOD-themed Plant Walk with the local Milo Baker chapter of the California Native Plant Society was postponed, discussions are underway about creating a live virtual field trip in its place, complete with 360 degree photos of highlighted spots along the trail. Similarly, SOD Specialist Master Gardeners have been presenting at public library series' for years, and are now hoping to create a recorded version to be posted on UCCE Sonoma's Sudden Oak Death webpage. Check back for announcements on these and other happenings.
Our gratitude goes out to every volunteer who has invested their time in staying educated, spreading the word, and participating in citizen science with us over the years, especially during the current shelter-in-place, with special recognition for our dedicated team of SOD Specialist Master Gardeners. We couldn't help our oaks without you!
- Author: Karen Giovannini
We are pleased to share our 2019 Annual Report available in two formats! We have our print version and are excited to present our story map version!
Special thanks to Michelle Nozzari for putting together the story map version and Deborah Curle for the print version.