Frequently Asked Questions
Why is it called "prescribed" burning?
The word "prescribed" is used to describe fires that are lit intentionally within our local State Parks because they are ignited under a specific set of environmental conditions that collectively constitute a prescription. These conditions typically include temperature, wind speed and direction, fuel moisture, and relative humidity, but seasonality and other factors may be included. The prescription is developed to meet specific goals and objectives that are developed by State Park staff and partners who possess deep knowledge of fire behavior and local ecology. It must be followed to safely and effectively conduct the prescribed fire operation, which we is often referred to as a prescribed burn or a controlled burn. The prescription will also specify whether fire will be contained to piles of dead vegetation (pile burning) or if it will intentionally spread through a specified area (broadcast burning). There are other types of beneficial fire, sometimes referred to as “good” fire beyond prescribed fire, including cultural burning and managed wildfires. The California Wildfire and Forest Resilience Taskforce provides more in depth information about beneficial fire across the state.
An image from a prescribed pile burn in Bothe-Napa Valley State Park in 2023.
An image from a prescribed broadcast burn in Jack London State Historic Park in 2022.
Human and lightening ignited fires have played a key role in defining California’s landscapes for many millennia. Many plants and animals are well adapted to, and sometimes depend on fire to move through their life cycles. California has a Mediterranean climate. That means that we have relatively warm, dry summers and cool, wet winters. Plants grow during the winter and spring and then act as potential fuel for fires in the summer. This plant material does not decompose very quickly in many of the ecosystems in the Bay Area District’s State Parks and over time accumulates due to California's dry summers. Without fire to recycle this built up dead plant material, it accumulates and can cause more intense fires when it does burn. This can pose heightened risks to people as well as plants and wildlife that have evolved with and are adapted to less intense fires. As Californians, we don’t get to choose whether our landscapes burn, but we can influence when and how fire moves through the landscape in some situations.
Almost all of California’s landscapes have evolved with fire, so fire is an integral part of stewarding them. Prescribed burns return nutrients to the soil, stimulate plant growth and germination, and help sustain the complex mosaic of plant communities that support California's tremendous biodiversity. Prescribed burns can also remove fuel from the landscape making it safer for people and helping State Parks conduct targeted stewardship of vegetation, including the management of invasive species.
Safety is always the first consideration. There are many places that could benefit from prescribed burn that, for a variety of reasons, are not appropriate for prescribed fire. Where fire can safely be applied, its anticipated effects on the plant and animal communities is the next consideration. After that, details of when and how to apply fire to the area to achieve the desired result are considered.
Favorable weather and availability of necessary fire suppression resources to safley conduct a given burn are the primary drivers for prescribed burn scheduling. Provided that these can be accounted for, prescribed burns are timed to maximize the potential for us to meet the desired fire effects (such as percentage of live and dead plant material to be consumed in the burn) and minimize adverse impacts to plants and wildlife. The times at which all these conditions overlap are referred to as a burn window. California's climate generally dictates that we have relatively warm, dry summers and cool, wet winters.
Pile burning can regularly be scheduled through the rainy season to take advantage of burn windows where the fire is unlikely to spread, though burning wet fuels can create more smoke. Wax paper is sometimes used to cover piles to keep a portion of them dry to allow personnel to ignite them efficiently, and help reduce smoke generated from the burns. Given that piles tend to burn at a high intensity, pile burns are seldom conducted during late spring, summer and fall at times when the adjacent areas will support fire spread unless there are sufficient measures in place to contain the fire to the piles or a predetermined area immediately around them.
Broadcast burning requires vegetation to be dry enough to support fire spread, but not so dry as to lead to adverse fire effects. Plants grow during the winter and spring and are generally vulnerable during these periods. If the goal of a given prescribed burn is to kill or reduce the abundance of invasive plant species, the burn may occur as soon as vegetation has dried out enough enough to burn in late spring or early summer. Most broadcast burning in the Bay Area District’s State Parks is timed for the late summer and fall, at the end of fire season but before significant rains, to allow the fire to effectively burn to meet objectives while accounting for safety considerations.
This depends primarily on the vegetation that is being burned, the size of the prescribed burn, and how well the smoke disperses.
Prescribed burns in grasslands of up to several hundred acres can sometimes be safely conducted in a single day with very little residual fire or smoke. Shrubs in these areas may burn for a handful of days after the burn has been completed, producing some smoke.
Pile burns can be completed over the course of a day, or longer depending on the type and size of material in the piles.
Prescribed burning in forests, sometimes referred to us understory burning, typically takes much longer. This is due to the larger fuels that can burn for multiple days after being ignited. Allowing these large fuels to fully burn down is one of the most significant benefits of broadcast burns in forested ecosystems and is a critical reason State Parks conducts prescribed burns in these areas. The portion of the burn when fire is actively being lit may take one or multiple days to ignite in these burns. Some smoke may be produced for days or at times over a week following ignition of the burn, with the fire to only be completely extinguished once it rains enough to fully saturate the burning wood.
Prescribed burns are carefully planned by staff with extensive training and experience. Prescribed burn plans are reviewed by CAL FIRE, the State’s fire suppression agency or at times local fire agencies with jurisdiction, such as the Marin County Fire Department, who also permit burning throughout much of the year. Most prescribed burns in Bay Area District Parks are generally supported and/or led by staff from one of these fire agencies. Burn plans list the set of environmental conditions under which the fire can be lit (the prescription), and what resources must be available (fire fighters, fire engines, helicopters, etc.) either on site or in contingency prior to ignition. Prescribed fires generally start with a small test burn to determine how smoke will disperse and whether it is safe to burn, at which point a decision about proceeding will be made only if it safe to do so. A prescribed fire can be cancelled at any time prior to or after its ignition if these factors or other safety concerns warrant the cancellation of a burn. If the burn has already started, this may require the suppression of the fire which can take time, especially in forested areas.
State Park staff work closely with our local air districts who model and forecast expected smoke dispersal and adjust our plans to limit smoke production when it is likely to have negative impacts on the community. The Bay Area District's State Parks all fall under the jurisdiction of the Bay Area Air Quality Management District. Burns are sometimes postponed or canceled if there is a high potential for them to pose adverse impacts on air quality to protect the health of our surrounding communities. Prescribed burning produces significantly less smoke then wildfires and is always announced, allowing people to plan accordingly to reduce their exposure.
Most animals are adapted to fire and depend on the food and habitat opportunities it provides to exist in our parks. Animals generally either leave the area or seek refuge underground or in moist places during a prescribed burn, often returning shortly after a burn has been completed. In many cases wildlife use burned areas consistently in the days and weeks following a prescribed burn to graze on fresh growth, hunt in more open areas and even to new build homes that may be less likely burn in a future wildfire.
While most animals are unharmed by prescribed burns, some are adversely impacted by prescribed burns, but many fewer than in fast-moving wildfires. Most prescribed burning in the Bay Area District’s State Parks happens seasonally to avoid periods of nesting when many local animals may be raising young and might be unable to leave a burning area. When these seasons can’t be avoided, biologists conduct surveys to identify nests or other sensitive areas and determine appropriate protection measures. Broadcast and pile burns are always ignited intentionally in the manner to allow wildlife in piles or burn areas to exit. Many animals temporarily leave these areas due to the presence of the people and fire equipment in the days leading up to and during the implementation of a prescribed burn, and frequently return shortly after a burn is completed.
Prior to igniting a prescribed burn, California State Parks makes every effort to inform the community. This includes updates to our park websites and social media accounts, the posting of signage in the parks as well as the dispersals of press releases to local media outlets. If you see smoke or fire coming from a state park and are not sure, you can look to these places as well as websites and social media accounts connected to CAL FIRE's Sonoma-Lake-Napa Unit and local fire departments. Wildfire alerts and evacuation updates will also be shared by Sonoma County, Marin County and Napa County through thier local emergency alert systems. There are a number of websites (also available as smartphone apps), such as Watch Duty and PulsePoint, that will alert you about wildfires and may also provide information about prescribed fires.
For prescribed burns conducted in state parks in the Bay Area District’s State Parks, check this website and feel free to reach out to contact information listed on press releases. Announcements and updates are also made on social media pages and individual park websites when a burn is planned or has recently occurred in a State Park, and broadcast burn projects will be posted directly in the Watch Duty app, with the incident updated as time permits prior to and during a burn. We also recommend following CAL FIRE's Sonoma-Lake-Napa Unit and the Marin County Fire Department on social media for updates on their agency's prescribed burns and wildfire response in our area.
Call the Bay Area District Office (707) 769-5652 or email BayAreaNaturalResources@parks.ca.gov. A phone number and email for public information contact(s) will be provided on signage and in press releases and website updates for any given prescribed fire.
