Fire damage from the 1991 Oakland Hills fire. Buildings can burn quickly if embers get inside and fall on flammable materials.
Preventing embers from getting inside may save homes
Photos and video of the Northern California communities that have been hit by wildfires this week show buildings reduced to ash. How could so many homes and businesses burn so quickly in Wine Country fires? Many houses that burned to the ground in the Northern California fires likely burned from the inside out, says Yana Valachovic, UC Cooperative Extension forest advisor for Humboldt and Del Norte counties.
Red hot embers carried on the wind can enter the attic via the venting. “In the case of the wind-driven fires on October 8, these fires created ember storms that blasted little coals into everything in their pathway,” Valachovic said. These embers also create small spot fires near the home that fuel new sources of embers.
Weather played a large role in these fires and generated a fire storm of embers that ignited grass, shrubs, trees and anything in its path. “While the landscape can be the fuse, the homes really can be the most burnable part of the landscape,” Valachovic said. “These embers likely lodged in the small spaces and openings of homes and buildings. A common location is for the embers to enter via attic venting or HVAC systems distributing little fires into the buildings.
“Embers also landed on receptive leaves, outside furniture, and other flammable materials outside the buildings that created fires adjacent to the buildings. Once enough buildings were engulfed in fire, the radiant heat of each building fire led to exposures on the neighboring buildings, creating a house-to-house burn environment.”
Embers carried on the wind can ignite dry plant material like pine needles and create more embers that may enter homes through vents.
Residents can reduce the risk of embers setting their house on fire by removing dry plants around the structure.
“These fires remind us that everyone in California could help the fire situation by managing the vegetation, leaves in the gutters and decks, newspaper piles, brooms and other flammable sources near to their houses now before they get the evacuation call,” Valachovic said. “If you are likely to have to evacuate soon, temporarily covering or sealing up the vents with metal tape or plywood can help harden your home to an ember storm.”
Steve Quarles, UC Cooperative Extension advisor emeritus, who spent his career studying fire behavior on building materials and around homes, created an online Homeowner's Wildfire Mitigation Guide at http://ucanr.edu/sites/Wildfire. Quarles, who now does research for the Insurance Institute for Business and Home Safety, demonstrates how embers can ignite and quickly engulf a house in flames in a video https://www.youtube.com/watch?v=IvbNOPSYyss. After the 3-minute mark, video shows embers drifting up and flying through a screened vent into the house, where they could ignite combustible materials in the attic resulting in fire starting on the inside of the home.
Yosemite Valley in the western Sierra Nevada Mountains.
What if nature were to become a polluter, discharging millions of tons of planet-warming carbon into the atmosphere in much the same way as diesel-fueled trucks or coal-fired power plants?
This nature-as-polluter scenario might seem far-fetched, but it's well on its way to becoming reality, according to a recent study co-authored by UC Merced Professor LeRoy Westerling.
In a paper published recently in Scientific Reports Opens a New Window.— “Potential decline in carbon carrying capacity under projected climate-wildfire interactions in the Sierra Nevada” — Westerling and collaborators from the University of New Mexico and Penn State University used three climate models and data from the Intergovernmental Panel on Climate Change to examine how rising global temperatures and increasingly severe wildfires will affect Sierra Nevada forests.
Their conclusion: Changing conditions will turn today's Sierra Nevada forests into tomorrow's greenhouse gas emitters.
“Forests play an important part in regulating the levels of atmospheric carbon,” Westerling explained. “Forests are carbon sinks, essentially giant stockpiles of carbon. Forests are also active carbon consumers. They remove carbon dioxide from the air and convert it into biomass. This traps the carbon, which is no longer free to act as a greenhouse gas in Earth's atmosphere.”
Professor LeRoy Westerling
But projections from Westerling and colleagues suggest that this may change. According to their models, Sierra Nevada forests will experience both a dramatic loss of stored carbon and a substantial decline in their ability to remove CO2 from the atmosphere.
Rising temperatures are creating a warmer, drier Sierra Nevada climate. Westerling previously showed that these changes are leading to dramatic increases in the frequency, size and duration of wildfires. The new study suggests that these same changes will make it harder for forests to regenerate, leading to a loss of forest density, with plants better suited to the new climate eventually replacing trees.
“As trees are displaced, the Sierra Nevada will lose its ability to sequester carbon,” Westerling explained. “The plants that spring up in their place will be significantly smaller, making them less effective carbon sinks than the trees they replaced.”
But the carbon stored in forest trees has to go somewhere.
As trees are burned in more frequent wildfires, and as dead trees undergo decomposition, Westerling and his colleagues predict that as much as 73 percent of the carbon in Sierra Nevada forests will be released, resulting in a dramatic spike in atmospheric carbon. This will transform the Sierra Nevada from a carbon sink into a carbon emitter, making the nature-as-polluter scenario a reality.
Westerling and his collaborators note that their predictions are actually conservative. The effects might be more extreme than their models suggest.
“Our study does not account for a number of factors that might influence the dynamics of forest carbon,” Westerling said. “However, the factors we ignored are likely to accelerate the loss of forest. Our predictions likely underestimate the severity of actual effects.”
Though the predictions are alarming, the authors remain optimistic, hopeful that their findings can contribute to a larger conversation about environmental policy and promote avenues of research that lead to sustainable forest management.
In response to California's growing tree mortality crisis, the Little Hoover Commission held a public hearing on California Forest Management yesterday (January 26) at the state capital in Sacramento.
Professor Scott Stephens, a fire scientist in the department of environmental science, policy, and management, delivered the opening remarks. He provided background on the causes and magnitude of tree losses happening across the state. "Our forests are not in a resilient condition," he said. "Past management actions, including fire suppression and logging focused on large trees have produced forests today that are much more vulnerable to fire and drought-related mortality." Stephens made suggestions for legislation, policy, and forest management techniques that could help restore resilience to California's forest ecosystems and prevent future mortality crises. He also offered ideas on how the state could better work with private landowners as well as the federal government to promote healthier forests.
Research ecologist Rahel Sollmann receives UC President's Award to study fire impact on forests
The King Fire, which burned more than 97,000 acres in El Dorado County in 2014, will be studied by UC Davis ecologist Rahel Sollman and others. The other photo of Rahel, let's crop and use as an inset. (U.S. Forest Service)
RahelSollmann, an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology, is one of three recipients of the 2017 Research Catalyst Awards announced recently by University of CaliforniaPresidentJanetNapolitano.
With the $271,000 in funding provided by the award, Sollmann, a quantitative ecologist, will help analyze how megafires disrupt the forest ecosystem and food web and pollination networks. She will work with UC Berkeley Associate Professor Justin Brashares and UC Santa Barbara Assistant Professor Hillary Young, as well as other researchers at UC Davis and the U.S. Forest Service. Their research will focus on the King Fire, which burned more than 97,000 acres in El Dorado County in 2014.
“Forests are really at the heart of California economy, culture, and its ecological heritage,” Sollmann said. “The Forest Service has identified these large fires as the major threat to the integrity of California forests. We really hope to understand how large fires change forest pollination and food networks.”
Rahel Sollmann (John Stumbos/UC Davis)
Napolitano launched the President's Research Catalyst Awards in 2014tofostermulticampus, interdisciplinary research in areas of strategic importance to California and the world. Since its inception, the program has provided nearly $10 million for research focused on climate change, cultural preservation, drought, basic science, and other areas. It has created research opportunities for 50 UC faculty, nearly five dozen graduate students, and 20 undergraduates. The three awards, totaling more than $2 million, involve faculty and students from across the university with lead campuses at UC Santa Barbara, UC Santa Cruz, and UC Davis. The other projects include research led by UC Santa Barbara aimed at improving teacher training and student outcomes in California's K-12 schools ($1.5 million); and a UC Santa Cruz project ($278,000) to enhance knowledge of humanhealththroughpaleogenomic research.
Rahel Sollmann Recipients were selected following a highly competitive review process. A panel of experts evaluated applications based on scholarly merit and likely impact. President Napolitano selected the winners from among the top-ranked proposals representing all areas of university scholarship. Funding for the Catalyst Awards comes from the UC president's endowment funds, which support systemwide initiatives and projects.
Only about half of conifer trees regenerated five to seven years after wildfire in sites studied.
Study spanned 10 national forests and 4 burned areas in California.
Study presents tool to help foresters prioritize which lands to plant after a wildfire.
A study spanning 10 national forests and 14 burned areas in California found that conifer seedlings were found in less than 60 percent of the study areas five to seven years after fire. Of the nearly 1,500 plots surveyed, 43 percent showed no natural conifer regeneration at all.
The study was co-led by UC Davis and the USDA Forest Service and published December 21 in the journal Ecosphere. It presents a tool to help foresters prioritize which lands to replant immediately after a fire, and which lands they can expect to regrow naturally.
“High-severity fires are knocking out seed sources and leading to a natural regeneration bottleneck, which poses a predicament for the sustainability of our forests,” said lead author Kevin Welch, a research associate with the UC Davis Department of Plant Sciences.
For example, 10 of the 14 burned areas in the study, which include well-known wildfires like the Moonlight (2007) and Power (2009) fires, did not meet Forest Service stocking density thresholds for mixed conifer forests, making them good candidates for replanting and restoration efforts.
“Knowing that the Forest Service doesn't have the time, budget and staffing levels to restore everything, we basically want to help foresters predict what will be there five to seven years later so they can better focus restoration efforts,” Welch said.
How Does The Tool Work?
The researchers surveyed a range of elevations, forest types and fire severities –including in the Sierra Nevada, Klamath Mountains, and North Coast regions –to determine which factors promote and limit natural conifer regeneration and how different conifer species respond after a fire.
Using a simple tool developed by the research team, a manager can enter the forest the year following a fire and take a few field measurements –including distance to seed source, slope, and the cross-sectional area of living trees in the nearby forest. They can then predict whether a severely burned site is likely to meet a desired level of tree density five to seven years later.
Tested against four wildfires that were not in the study, the researchers found the tool was able to predict with more than 70 percent accuracy whether an area would likely need to be replanted or not.
The study plots were in California, but the authors suggest study results could apply to mixed conifer forests across the North American Mediterranean Climate Zone, which stretches from southwestern Oregon through California to northern Baja California and includes parts of western Nevada.
A Race For The Sun
As the research team saw while hiking through miles of dense brush, high-severity fires also stimulate shrub growth to the detriment of fire-resistant tree species that foresters try to encourage. The conifer regeneration that is occurring is heavily dominated by species that tolerate shade but not fire, such as Douglas fir, white fir and incense cedar.
Fire-resistant and drought-tolerant trees, such as ponderosa, sugar and Jeffrey pine, do not tolerate shade well. Such species are likely to better withstand the warmer, drier climates projected for California in the future.
Currently however, forest and fire conditions are not favorable for the survival of these more desirable trees. According to the study, strategies for increasing pines in California forests include reducing forest densities and fire severities while increasing overall fire occurrence (both prescribed fires and managed wildfires). They also suggest planting pines before shrubs and shade-tolerant trees crowd them out and remove their light source.
“As western forests increasingly experience warmer weather and more frequent and more severe fires, a better understanding of what conifers need to regenerate naturally after fire can help us create and manage more sustainable, resilient forests,” said co-author Hugh Safford, regional ecologist for the USDA-Forest Service's Pacific Southwest Region and a member of the adjunct faculty in the UC Davis Department of Environmental Science and Policy.
The study was funded by the USDA Forest Service and UC Davis.