Posts Tagged: wildfire
In less than a decade, some of the burned expanses from this year's megafires could burst into intense flames again, reported Ula Chrobak in Scientific American.
Frequent, low-severity fires, which clear out patches of low-lying vegetation and dry leaf litter, have an preventative effect. Research shows that areas burned by megafires are more likely to become susceptible to fires again.
UC Cooperative Extension forestry advisor Susie Kocher said that a century ago, before officials quashed all wildfires, only 5% to 10% of Sierra Nevada fires would burn at high severity. Today, the proportion of high-severity fires is between 40% and 60%.
“That's way outside of what we think would have been natural,” Kocher said.
After high-severity fires, the landscape is scorched and shadeless. Without mother trees, it may take a long time, or even be impossible, for conifers to move back in. With open land and sunlight, shrubs sprout amid downed dead pines, which over time accumulate dead twigs and leaves. If there is a spark, the shrubbery and fallen wood can sustain another large fire.
“Ultimately, all of these lands are going to need management within anywhere from two to 10 years —and probably closer to two to five years after a fire—to maintain that reduction in fuel,” said Kate Wilkin, a fire scientist at San José State University. As climate change makes California hotter and drier, increasing the propensity for monstrous fires, this need will only grow.
After another record year for California wildfire, concern is now turning to the soil impacted by firestorms, reported Sarah Klearman in the Napa Valley Register.
High-temperature flames can incinerate vegetation and destroy plant root systems, said Toby O'Geen, UC Cooperative Extension soil specialist at UC Davis. The loss of vegetation destabilizes the landscape, making it vulnerable to serious erosion or flooding.
"The most important way to battle erosion is to have surface cover - living vegetation anchoring your soil," O'Geen said. "We have none of that. If you have soil with existing susceptibility (to erosion) and now nothing to hold it in place, it's a new disaster."
Particularly catastrophic fire can make the soil surface water repellent, which allows water to pond up and release higher concentrations of run-off water even when rainfall is low.
"That creates more massive erosive events - it gives rise to accelerated erosion, and in some extreme instances, mudslides," O'Geen said.
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 on YouTube.
“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.
Additional resources and information shared during the webinar include:
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 on this web page. To view a past webinar recording with these research findings, click this link.
- Poultry wildfire resources from the UC Davis School of Veterinary Medicine:
- 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
In California, most ghost towns were created when a local industry collapsed. Now, climate change is more often to blame when booming communities whither and die, reported Daniel Cusick in E&E News.
In an eerie horror story released just before Halloween, Cusick wrote about five towns around the nation that have died or are dying from climate-related disasters. Historic Shasta and Helena, Calif., are featured in one of the vignettes.
"Those are two towns that are getting more ghostly," said Yana Valochovich, UC Cooperative Extension forestry advisor in Humboldt and Del Norte counties.
A 19th-century mining town, Shasta City had been a preserved tourist destination in Shasta State Historic Park since 1937 when it was burned in the 2018 Carr Fire, the seventh most destructive wildfire in California history. Helena, a 170-year-old pioneer mining settlement, burned in the Helena Fire of 2017.
There almost certainly will be more "dead towns" as fires consume more of Northern California, Valochovic added.
Improved soil health, increased profitability, and reduced spread of wildfire are among the many benefits that arise from keeping livestock on the landscape. Efforts are underway in California and South Dakota to connect landowners with livestock managers for their mutual benefit.
Farmers can increase the organic matter in their soil and reduce their fertilizer costs by allowing livestock to graze crop residue or cover crops on their land.
Nick Jorgensen, CEO of Jorgensen Land and Cattle in Ideal, SD, said that grazing every acre allows his operation to increase soil organic matter by up to 0.75% per year and cut fertilizer costs by $50 per acre with no yield loss.
Livestock managers can rest their pastures and reduce their feed costs by seeking out crop residue, cover crops and additional pasture or rangeland for their livestock to graze.
Jorgensen said that grazing cattle on all crop and cover crop acres cuts his feed and manure management costs by up to $2 per head per day.
Grazing livestock is also a cost-effective way to reduce the accumulation of fire fuels on the landscape, helping to slow the spread of wildfires. This can be especially important for land that is too steep, rocky or remote for mowing or chemical treatment.
“I've noticed on several fires, including extreme fires, the fence lines where the fire just stopped. And the one variable, the one difference, was grazing,” CAL FIRE Battalion Chief Marshall Turbeville said.
As this year has proven, fire is a serious risk to California landowners. That's one reason University of California Cooperative Extension has launched Match.Graze. It's a map-based website designed to help livestock owners find pasture, rangeland, cover crops or crop residue available for grazing and help landowners find cattle, sheep, goats and other livestock to graze their land.
“Every property is different and requires thoughtful consideration of how it should best be grazed,” said Stephanie Larson, director of UCCE in Sonoma County, UCCE livestock and range management advisor and co-creator of the livestock-land matchmaking service. “UC Cooperative Extension is here to serve. Put Match.Graze to work, and let's prevent catastrophic fire while helping landowners and agriculture.”
California landowners and livestock managers can visit MatchGraze.com, set up a free account, create a pin on the map and find a grazing partner.
The California website is based on the South Dakota Grazing Exchange, the original site launched by the South Dakota Soil Health Coalition with work supported by Natural Resources Conservation Service, U.S. Department of Agriculture.
Many farms in South Dakota have moved away from livestock to focus on row crops. However, increased diversity and incorporating livestock are two key principles for good soil health management.
At www.sdgrazingexchange.com farmers can find livestock to graze their crop residue or cover crops in order to capture the soil health benefits for their cropland without having to own livestock. Similarly, ranchers can give their pastures and rangeland a rest and reduce their feed costs by finding farmers with cropland to graze.
The Match.Graze and SD Grazing Exchange websites are not limited to California and South Dakota. Users from anywhere in the nation can create accounts on either website and advertise their land and livestock. The more people who use the websites, the better resources they will become.
When landowners partner with ranchers to keep livestock on the landscape, everyone wins, so the SDSHC will work to help other states create Grazing Exchange websites and connect to the maps and users of Match.Graze and SD Grazing Exchange. For more information, contact Cindy Zenk, SDSHC coordinator, at (605) 280-4190 or email@example.com.