Chapter 1.3
Sensitive Lands and Wildlife Habitat

• ALL
• Remove Code Barriers
• Create Incentives
• Fill Regulatory Gaps

Defensible Space Ordinance

INTRODUCTION

Over the past several decades, wildfire risk and its associated impacts on communities has been increasing across the United States.[1]The National Centers for Environmental Information (NCEI)[2] reports over $79.8 billion in costs associated with the occurrence of wildfires in the United States between 2018 and 2021.[3] In 2023, NCEI estimated there to be $135.5 billion in costs associated with wildfires since 1980.[4] Although the United States is not the only country that has been afflicted with the negative costs of wildfires (i.e., Greece, Canada, Australia), the United States has its share of costs associated with wildfires. The recent events in Lahaina, Maui, Hawaii, have been predicted to cost insurers an astonishing $3.2 billion.[5] In 2022, the nonprofit First Street Foundation identified California, Texas, Florida, Arizona, and Oklahoma as states with the largest number of properties that had at least a 1% likelihood of burning in the next 30 years.[6] Because of this risk, and the history of devastation in many Western states, some local governments have enacted local ordinances to minimize damage from wildfire in the built environment. One such ordinance is a defensible space ordinance. Although the term “defensible space ordinance” will be used throughout this brief, several other names refer to this practice.[7]

There are many strategies local governments can implement to mitigate and adapt to wildfires.  While it takes a comprehensive approach to do so, a defensible space ordinance is an important step. A defensible space ordinance regulates combustible materials and vegetation in designated areas around inhabited structures.[8] This type of ordinance can help prevent or reduce the spread of fire to inhabited structures or other values at risk by reducing the prevalence of flammable materials or vegetation on a property.[9] As detailed further in “Effects” below, establishing defensible space reduces the likelihood of a home igniting by direct flame contact or exposure to the radiant heat of a wildfire.[10] Defensible space ordinances also help reduce ember production; this means that it also reduces the likelihood that embers will ignite a structure and spread to neighboring structures or surrounding vegetation.[11] Finally, slowing the progress of an approaching wildfire can also help keep firefighters safe while they access or defend a property.[12]

Local governments can incorporate defensible space ordinances and wildfires generally in several parts of their codes. For example, vegetation management requirements for landscaping or defensible space can be addressed through subdivision regulations, a zoning code, or a Wildland-Urban Interface (WUI) code.[13] Successful implementation of plans requires the commitment of resources – for example, grants to homeowners to help with the creation or maintenance of defensible space on their properties.[14] Engaging community stakeholders and the public in the planning process can also build knowledge around actions that residents can take to reduce wildfire risk on their own properties, including creating defensible space.[15]

When a local government decides to enact a defensible space ordinance, it can be as simple as implementing minimum setbacks or as detailed as directing where and when a property owner can plant certain species of trees, plants, shrubs, or other landscaping materials. The grouping of vegetation may be implemented to further ensure that the plants’ water needs are satisfactory to the type of environment. Local governments may also enact certain height restrictions for trees and bushes to reduce their ignition potential from overhead powerlines and contacting the conductor. Additionally, local governments may limit which type of land uses, landscaping, or construction projects must follow defensible space requirements (i.e., single-family residences with landscaping plans of a certain size).

The implementation of a defensible space ordinance should begin by determining if there are any state minimum requirements in place or recommended guidance documents available. This ensures that local ordinances meet or exceed state requirements, or, at a minimum, align with research and best practices for the local environment. This information is typically available through state forestry, fire, and/or natural resource protection agency websites.

The State of California, for example, has a law that requires property owners in an area known to be responsible for clearing out flammable materials such as brush or vegetation around their buildings to 100 feet (or the property line) to create a defensible space buffer.[16] This state requirement is enforced by the California Department of Forestry and Fire Protection (“CAL FIRE”) Office of the State Fire Marshal.[17] Pursuant to the California statute, local governments with public and private properties upon or adjoining mountainous areas, forest-covered lands, shrub-covered lands, grass-covered lands, or lands covered in flammable materials must follow the minimum defensible space statute.[18] Importantly, the California statute allows local governments to increase the defensible space distance and to specifically manage the types of plants allowed in the defensible space area.[19] California law also permits local governments to pass defensible space ordinances in Local Responsibility Areas (“LRA”).[20] However, the LRA must be within an area deemed to be “a very high fire hazard severity zone designated by the local agency.”[21] The local agencies requirements are also governed by California law and give the local agency discretion in determining very high fire hazard severity zones.[22]

Because California’s defensible space statute sets a statutory minimum, many local governments have adopted a set of requirements for project planning and landscape development that meets or exceeds the state’s defensible space statute.[23] Such additional provisions are detailed in the Examples section below. Other provisions found in state minimums may include irrigation systems[24] and specific plant species prohibitions.[25]

In addition to California, Oregon, and Washington have implemented defensible space laws that contain provisions local governments – typically those that are in defined wildfire hazard or risk areas – must comply with and others that local governments may consider.[26] Oregon’s statute sets the defensible space requirements through a biannual study of fire hazard done by the state’s fire marshal. The State’s defensible space requirement, however, may not exceed standards that are set forth in the International WUI Code published by the International Code Council (ICC).[27] The ICC’s WUI Code §§ 603 and 604[28] states that certain property interface areas shall be required to maintain a defensible space dependent upon the hazard level of the property.[29] The WUI Code also recommends the regulation of tree growth,[30] chimney clearance,[31] and deadwood removal.[32]

Washington State also adopts the ICC’s WUI Code,[33] and states that State “governing documents may not prohibit the installation of . . . wildfire ignition resistant landscaping.”[34] On May 12, 2023, Colorado took a step towards the creation of a defensible space regulation through the creation of a Wildfire Resiliency Code Board, which is empowered to create a statewide minimum code for fire-resistant construction and defensible space in Colorado’s WUI areas.[35]

EFFECTS

In areas where defensible space ordinances are enacted, they can reduce the damage to homes and communities, and can play a key role in saving lives, biodiversity, and property loss.[36] Wildfires are global phenomena exacerbated by climate change that pose significant risks to life and property. The immediate health effects of someone exposed to smoke from a wildfire are stinging in the eyes, increasing production of mucus sometimes turning black in color, tightening of the airways, and exacerbating respiratory problems like asthma and chronic obstructive pulmonary disease (COPD).[37] There has been a minimal amount of research done on the continued inhalation of wildfire smoke.[38] However, in a study of firefighters exposed to wildfire smoke in cumulative short-term periods, their lung function and capacity decreased.[39] The effects of exposure can persist for years. After Australia's 2014 Hazelwood Coal Mine fire, rates of heart disease remained elevated for two and a half years and respiratory illnesses for five years.[40] Canadian researchers have reported that people who lived outside of major cities and within 50 kilometers (31 miles) of a wildfire in the past decade had a 4.9% higher risk of lung cancer and a 10% higher risk of brain tumors compared to people not exposed to wildfire.[41] Influenza rates in the winter influenza season were 16 percent to 22 percent higher when average daily exposure to PM_2.5 during wildfire season increased by 1 microgram per cubic meter.[42] Thus, a defensible space ordinance may decrease the health impacts on citizens by decreasing the likeliness of wildfire continuously spreading.

The psychological effects of wildfires should not be ignored. Many studies have claimed the exacerbation or formation of significant mental health problems following a wildfire. Specifically, one study found that rates of post-traumatic stress disorder (PTSD) after wildfire exposure among adults were 24% to 60% at 3 months, 12.8% to 26% at 6 months, and 10.2% to 13.6% at 18 months.[43] Rates of PTSD in children and adolescents ranged from 9% to 29.4% at 6 months and 27% to 37% at 12 months post wildfire.[44] Interestingly, in a study determining the psychological impacts of wildfires upon children with already existent developmental disabilities, the participants who were involved with the 2017 Northern California fires “exhibited stress, grief, and other emotional and behavioral reactions during evacuation, in the immediate aftermath, and 1 year post-disaster.”[45]  As such, “[p]roactive climate adaptation requires a set of resilient personality traits and lifestyle factors that preserve mental health and facilitate a much-required cultural shift towards sustainability.”[46] One such cultural shift could be defensible space ordinances, which may decrease the psychological impacts of wildfires.

By reducing the number of structures burned by wildfires, defensible space ordinance can help reduce the amount and types of toxins that pollute the air, soil, and water. When wildfires burn, they release numerous toxins into the surrounding ecosystems. Such toxins can negatively impact the adjacent humans, fauna, and flora. For, example, in November 2018, the Camp Fire in Northern California destroyed over 150,000 acres, 13,972 residences, 528 commercial structures, and 4,293 other buildings, and tragically claimed the lives of 86 people.[47] The burning of these structures resulted in significant releases of toxins, including the contamination of local drinking water with the cancer-causing chemical benzene.[48]

Defensible space ordinances may also reduce costs associated with wildfires. Wildfire costs are borne by several different parties, including residents and families of impacted areas, property owners, insurance companies, electric utilities, taxpayers across the country, and others.[49] When wildfires occur, they can bring additional and unexpected costs to homeowners. This may result in delayed mortgage payments, restricted access to future credit, and increased lenders’ exposure to default risk.[50] Insurance and government aid exist to mitigate this default risk, but these protections have been weakening because insurers have been reducing coverage.[51] Plus, many homeowners are unable to access or afford home insurance.[52] Thus, to avoid property damage, and the shocking costs that follow, homeowners and local governments would be well served to implement defensible space ordinances.

In a scenario where wind or external factors cause a wildfire to reach a property with a defensible space, the space cleared around that home provides a safer means for firefighters to access the home and conduct defensive actions.[53] Firefighting efforts can be more successful in defensible space communities than in others because, with space cleared around homes and buildings, firefighters are able to reach the fires with their equipment, trucks, and hoses and put the fire out more quickly.[54] In most landscapes, mitigation efforts can improve aesthetics and wildlife habitat as well as reduce wildfire threat.[55]

EXAMPLES

Malibu, CA[56]

Although the baseline governing statute still lies at the state level, Malibu, California implemented the stricter Ordinance No. 461 § 17.53.080 that guides construction companies and landowners on fire protection standards. The ordinance covers any “industrial, commercial, institutional, or multifamily use or subdivision, any of which propose a new or altered landscape area, including public agency projects.”[57] The Ordinance also covers any “single-family residential use proposing a new or altered landscape area of five hundred (500) square feet or more.”[58] When a single-family residence already exists and is involved in an otherwise applicable project, the landscape is subject to this Ordinance when the single-family residence is two thousand five hundred (2,500) square feet or more.[59] Single-family residences that must rebuild after a natural disaster, are required to follow the fire protection provisions.[60] The Ordinance exempts several projects including historic sites, ecological restoration, mined land reclamation, botanical gardens, and cemeteries.[61]

Malibu’s Ordinance follows the state minimum for defeasible space feet and requires plants to be grouped into “hydrozones,” where the plants have similar water demands.[62] The Ordinance defines a “hydrozone” as “a portion of a landscape area having plants with similar water needs that are served by an irrigation valve or set of valves with the same schedule. A hydrozone may be irrigated or non-irrigated.”[63]

The Ordinance also requires plants to be approved under a maximum applied water allowance (“MAWA”).[64] A MAWA measurement is different for commercial and residential projects, and the maximum allowance is measured using equations within the ordinance.[65] No residential or commercial projects can involve turf, unless the turf is used as a “bio-swale or bio-filter systems, or areas adjacent to pedestrian traffic where walking travel or crossings are expected.”[66]

The Ordinance also prohibits certain species that may fuel fires.[67] For example, there is a flat prohibition on palm trees.[68] Trees and shrubs are prohibited between zero and five feet from a structure.[69] Eucalyptus (Eucalyptus gum tree), Pine (Pinus species), Cypress (Cupressus species), Cedar (Cedrus species), and Tree of Heaven (Ailanthus altissima) are prohibited within 50 feet of a structure.[70] However, eucalyptus trees are allowed from 5 to 50 feet from a structure when an expert designates that area as a monarch butterfly habitat.[71] The Ordinance gives more detail on the planting distances in utility easements. Specifically, it limits the growth height to 25 feet when 20 feet or less from the utility easement and limiting the growth height to 40 feet when the tree is planted with 20 to 50 feet from the utility easement.[72]

Mulch must be either weed-free or inorganic material to avoid evapotranspiration,[73] and to lower temperatures of plant roots.[74] Mulch proposed between zero and five feet from a structure must consist of nonflammable materials, such as gravel and decomposed granite.[75] Flammable mulch, including shredded bark, pine needles, and artificial turf, are prohibited between zero and five feet of a structure.[76] Use of wood chips and shredded rubber is prohibited anywhere on the site.[77]

Pursuant to the Ordinance, before construction occurs, the applicant must obtain approval of a “landscape documentation package” which demonstrates compliance.[78] The landscape documentation package shall be designed in accordance with the landscape water conservation standards and the guidelines and shall include a landscape design and soils management plan, an irrigation plan and a water budget calculation worksheet.[79] Prior to certificate of occupancy or other final project sign off, the applicant must obtain approval from the director of a certificate of completion.[80]

To view the provision see Ordinance-No-361_Fire-Resistant-Landscpaing (malibucity.org).

Butte County, CA

Butte County, California implemented Ordinance Sec. 38A-6 that guides any person who owns, leases, controls, operates, or maintains any parcel within the unincorporated area of the County on defensible space and vegetation management.[81] The Ordinance supplements and is in addition to other fire prevention and protection statutes, regulations, and ordinances enacted by the state, the County or any other governmental agency having jurisdiction, including but not limited to the California Fire Code and Public Resources Code sections 4290 and 4291. The Ordinance requires that all combustible materials be removed from immediately around and adjacent to any building on the property. The Ordinance only permits vegetation with high moisture content, such as “flowers, ground covers, and green lawns, free of dead vegetative debris,” within five (5) feet of any building.[82] The Ordinance defines combustible materials as “seasonal and recurrent weeds, stubble, brush, dry leaves, mulch, wood, tumbleweeds, rubbish, recyclable material, litter or flammable materials of any kind.”[83] Butte County’s Ordinance requires the removal or pruning of flammable plants and shrubs near windows and under eave vents.[84] The Ordinance also calls for a 100 foot firebreak and within that firebreak there are certain restrictions.[85] Any portion of a parcel, improved or unimproved, within one hundred (100) feet of a building on an adjacent parcel must comply with the 100 foot firebreak requirements “in order to provide the adjacent building no less than one hundred (100) feet of defensible space.”[86]

The Ordinance requires the clearing of hazardous vegetation on each side of the driveway for ten (10) feet from the edge, and fourteen (14) feet tall from the surface of the driveway.[87] These width and height restrictions apply to all public and private driveways and roads.[88] However, when the property in question is on a fire evacuation route, as determined by the County Enforcement Official, there must be a firebreak of twenty (20) feet from the edge of a travel way.[89] The Ordinance outlines that certain specimen shrubs, specimen trees, and fire resistive vegetation can be retained within a firebreak with restrictions.[90] Specimen shrubs may be retained if they are spaced “no less than three (3) times their widest width” and are “fifteen (15) feet away from other specimens or buildings”[91] Specimen trees may be retained if they are “trimmed of limbs to a minimum of six (6) feet from the ground or one-third (⅓) of their height from the ground, whichever is lesser,” and “crowns of adjacent specimens are not interlaced to constitute a medium for the rapid spread of fire.”[92] Firebreaks may also retain any fire resistive vegetation (i.e., green lawns, ice plant, green ivy) or any plant which is “recognized by the Fire Chief as being fire resistive.”[93]

Finally, urban parcels must comply with all firebreak requirements, along with some additional requirements.[94] An urban parcel is defined in the Ordinance as “those parcels located in the unincorporated areas of the County that are inside the spheres of influence of the cities of Biggs, Chico, Gridley, Oroville, and Paradise.”[95] Urban parcels also encompass all parcels located outside the spheres of influence “but within an approved subdivision that has lots six (6) acres in size or smaller, where fifty (50) percent or more of the lots within such subdivision have been developed and improved with residences”[96] Urban parcels are required to follow all firebreak provisions discussed above, as well as two other requirements.[97] On unimproved urban parcels that are greater than one and one fourth (1.25) acre in size, firebreaks are required adjacent to and along all parcel boundary lines for a maximum width of thirty (30) feet.[98] “Required firebreaks may be created by mowing to a maximum height of four (4) inches, discing or removing the annual weeds, grasses, rank growth and trimmings, and by removing obstructions.”[99] Any and all utility generators running off of petroleum products must have a firebreak of no less than ten (10) feet above, around, and above.

To view the provision: Chapter 38A - FIRE PREVENTION AND PROTECTION | Code of Ordinances | Butte County, CA | Municode Library (Version: September 20th 2023)

Paradise, CA

Despite the California state statute, Paradise, California implemented Ordinance Sec. 8.58.060 which guides any person that owns, leases, controls, operates, or maintains any real property in the town to the standards for maintaining a defensible space. The Ordinance requires the owner to maintain a non-combustible five (5) feet immediately adjacent and around any building.[100] This Ordinance also maintains that any accessory dwellings or outbuildings be at least ten (10) feet away from the primary dwelling building.[101] Fencing materials used to build fences on the property, that are made of combustible materials, are to be placed no closer than five (5) feet from any building.[102] The fencing must also be in a single line.[103] Along with cleaning the gutters of any dead leaves or pine needles, the ordinance requires that any loose or missing shingles be replaced as to ember penetration.[104]

The Ordinance requires the maintenance of a firebreak of one hundred (100) feet from any building on the property.[105] Within these one hundred (100) feet, the ordinance requires that all weeds and dry grasses be mowed to no taller than four (4) inches.[106] The Ordinance also calls for ladder fuels to be removed. Ladder fuels are any vegetation, brush and small trees under mature trees.[107] When planting, trees and shrubs are not to be placed in groups larger than three (3).[108] However, this subsection of the ordinance does not apply to “single tree specimens, ornamental shrubbery, or similar plants which are used as ground cover and provided they do not form a means of rapidly transmitting fire from the native growth to any building or structure.”[109]

This Ordinance also applied to unimproved parcels. Unimproved parcels are defined as “a portion of land of any size, the area of which is determined by the assessor's maps and records and may be identified by an assessor's parcel number upon which no structure is located.”[110] The Ordinance applies to any unimproved parcel of one and one half (1½) acres or less, and the fuel modification must be implemented to the entire parcel.[111] The Ordinance requires that all weeds and dry grasses be mowed to no taller than four (4) inches.[112]  The Ordinance also calls for ladder fuels to be removed. Ladder fuels is any vegetation, brush, and small trees under mature trees.[113] Unimproved parcels greater than one and one-half (1½) acres in size are required to maintain a fuel break a minimum of thirty (30) feet from the property line, subject to the same standards as an unimproved parcel lesser than one and one-half (1½).[114]

As a requirement before the sale or transfer of title from one owner to another, the seller or transferor must obtain a permit of compliance from the town showing that the land is following this ordinance.[115] Also, grazing animals which are used as weed abatement may graze openly for a period of no longer than sixty (60) days during any given calendar year.[116] The fire chief of the town has the authority to inspect the property at any time there is a suspicion that there is a condition which does not conform with the ordinance.[117] Any person violating any of the provisions of the ordinance chapter is guilty of an infraction with fines, which accrues with each day of violation.[118]

To view this ordinance: Chapter 8.58 - DEFENSIBLE SPACE AND HAZARDOUS FUEL MANAGEMENT | Code of Ordinances | Paradise, CA | Municode Library ( Version: September 15, 2023)

Wenatchee, WA

Although the governing statute still lies at the state level, Wenatchee, Washington implemented Ordinance Sec. 3.36.160 which guides all newly constructed structures in the primary zone, except those “in the residential foothills low zoning district.” The required defensible space is thirty (30) feet in undeveloped land in the primary zone.[119] However, when the undeveloped land is adjacent to the westerly and northerly native wildland fuels, the defensible space must be one hundred (100) feet.[120] When the one hundred (100) feet of defensible space is required and there is a street between the structure and the wildland fuels, the defensible space may be seventy (70) feet.[121] The one hundred (100) feet of defensible space may also be decreased to eighty-five (85) feet if there is a gravel fire apparatus access road between the structures and the native wildland fuels.[122] A fifty (50) foot minimum defensible space from undeveloped land for structures on or at the top of the slopes must be maintained on the easterly side of the zone.[123]

The ordinance gives a variety of ways in which the defensible space may be maintained: 1) a modified fire-resistive perimeter area within a common lot or roadway outside of individual lot lines; and/or 2) a fire-resistive landscaped yard area within individual lot lines.[124] The ordinance requires all newly constructed structures in the primary zone be protected by a five (5) foot non-combustible surface extending from any exterior walls of the structure and the outer perimeter of any appendages and projections.[125] Wood fences and gates less than four (4) feet from the structure are prohibited.[126]

The ordinance, much like the California ordinances, implements certain landscaping requirements within the defensible space. The following characteristics of fire-resistant vegetation are to be maintained within the defensible space: 1) growth with little or no accumulation of dead vegetation, either on the ground or standing upright (juniper trees are prohibited); 2) nonresinous plants (willow, poplar or tulip trees); 3)  low volume of total vegetation; 4) plants with high live fuel moisture; 5) drought-tolerant plants; 6) stands without ladder fuels; 7) plants requiring little maintenance; and 8) plants with woody stems and branches that require prolonged heating to ignite.[127] Any violation of this Ordinance constitutes a code violation, for which a monetary penalty may be imposed.[128]

To view this ordinance: Chapter 3.36 WILDLAND-URBAN INTERFACE STANDARDS (codepublishing.com)

ADDITIONAL EXAMPLES

Coconino County, Arizona Zoning Ordinance §4.4.E Fire Protection and Weed Mitigation (all subdivisions and developments requiring a landscape plan located in the designed WUI must incorporate “Firewise” management practices into the design and maintenance of landscaping, with varying degrees of treatment based on three zones).

Napa County, California Code of Ordinances Ch. 8.36 § 60 (2019)(Version: September 12, 2023) (requiring, at the owner’s own expense, the removal of prohibited materials that contribute to the fuel load or hinder the clearing of properties or delay firefighting operations on any parcel).

Washington State Rev. Code Wash. (ARCW) § 64.38.057 (adopting standards of the International Wildland-Urban Interface Code (IWUIC), including method for determining defensible spaces based on the level of hazard; for moderate hazard, thirty (30) feet of defensible space is required; for a high hazard, fifty (50) feet of defensible space is required; for an extreme hazard, one hundred (100) feet of defensible space is required).

Ouray County, Colorado Building Requirements (requiring no less than one hundred (100) feet of adequate defensible space in all directions around the building; construction requirements for decks and fences; ignition resistant eaves and roofs; windows must have certain features, including insulated glazing).

ADDITIONAL RESOURCES

Community Wildfire Planning Center, Resources, https://perma.cc/3G49-5LXX (state and national guide to wildfire resources).

Community Wildfire Planning Center, Regulating the Wildland-Urban Interface in Colorado, Sept. 2022, https://perma.cc/GX46-NRYJ (detailing three Colorado communities wildland-urban interface regulations).