Sustainable Defensible Space

Protecting Homes and Landscapes Against Wildfires

By: Elisa Read Pappaterra Antoine Kunsch

Elisa Read Pappaterra is the Horticultural Specialist at RIOS, a multidisciplinary design firm based in Los Angeles. Elisa’s landscape focused research and…

More From This Author

Antoine Kunsch is the Community Resilience Coordinator of the Resource Conservation District of the Santa Monica Mountains and a Doctoral…

More From This Author

Woosley Fire in Malibu CA. Photo courtesy of Peter Buschmann

The 2020 California wildfire season has caused historic losses of life, property, and wildlands. Southern California, one of the most fire-prone environments in the world, has more homes and area burned per decade than any other region in the United States. As wildfires are part of the ecosystem, it’s of utmost importance we prepare our homes and property for this threat.

The Wildland Urban Interface (WUI)—structures and developed landscapes located within a mile of large open lands—is the area most susceptible to wildfires. In 2019, the Resource Conservation District of the Santa Monica Mountains (RCDSMM) received funding from the California Department of Forestry and Fire Protection (CALFIRE) through the California Climate Investments Program to create defensiblespace.org, a platform to improve the fire safety and habitat quality of the defensible space of homes in the WUI.

Logo of the website defensiblespace.org ©Resource Conservation District of the Santa Monica Mountains

The website introduces the notion of Sustainable Defensible Space, the area around the home extending up to 100 feet. The condition of this space is critical, not only to increase the resistance of structures to wildfire loss and safeguard firefighters, but also to improve conservation value and protect California’s natural heritage. The landscaping surrounding a home provides the greatest opportunity for improved habitat conservation, biodiversity support, and slope stability, as well as increased carbon storage and water conservation. 

Quercus agrifolia grove garden in Montecito CA © Elisa Read

Understanding the local environment and wildfire risk

We designed an interactive map within the website for residents to learn about the individual qualities of their location. It shows how a property fits within the local habitat types, for example, oak woodland, coastal sage scrub or chaparral. Users can explore past fires in their area, as well as the jurisdiction and protection plans established in their community. We hope this information helps residents understand their particular location, and how the decisions they make on their own property, and together as a community, can influence their vulnerability to wildfire.

The Community Risk section examines the outermost part of the defensible space zone, extending into neighboring properties. In order to maximize the benefits of home fire-wise landscaping, it is important for residents to work collaboratively with neighbors to understand the nature of shared risks and how to mitigate them.

 

Why is defensible space important?

The key to protecting homes and properties from fire in the WUI starts with the home. The Los Angeles County Fire Department estimates that embers cause the ignition of more than half of the homes that burn in wildfires. Fortifying or retrofitting a home can be the best defense against ember intrusion. Whether building a new home or retrofitting an existing one, the website details a number of things you can do.

 

Relative cost and priority level of home hardening features for fire-resistance. ©Resource Conservation District of the Santa Monica Mountains house

In addition, practicing appropriate landscape fuel management (ornamental or native), land maintenance, and thoughtfully selecting plants for a home’s defensible space zone are the next significant actions homeowners can take. The zone that contributes most to structure survival is within the first sixty feet from the home. The website’s section on home landscape management provides clear guidance with resources that are consistent statewide.

 

Design a native and fire-wise landscape

You can have both a beautiful native landscape and a fire-wise home though proper planning. The website’s recommendations for new and existing landscapes work in partnership with a seasonal maintenance checklist to help maintain a sustainable defensible space all year round.

 

Zone 0: The Ember-Resistant Zone (ERZ)

The Ember-Resistant Zone is the first five feet around the home, including the structure itself. The objective in this zone is to avoid ignitions from windblown embers landing on or near the direct surroundings of the house and starting a fire. Research from the Insurance Institute for Business and Home Safety (IBHS) shows that the first zero to five feet around the house has the greatest impact on reducing the risk of losing a home to wildfire. In the Ember-Resistant Zone, all home building materials, vegetation, equipment, outdoor furniture, toys, or anything else that could be ignited by embers must be removed or replaced. No landscape mulch or wood chips should be used; instead use clear soil, rocks, gravel or concrete.

 

The Ember-Resistant Zone extends five feet around the home. ©Resource Conservation District of the Santa Monica Mountains

Zone 1: The Home Protection Zone

The Home Protection Zone should be a landscape that, if ignited, will not transmit fire to the home. Depending upon the type of wildland vegetation in the area and the steepness of the slope, this zone should have an area at least thirty feet wide (fifty feet for slopes above twenty percent) that is lean, clean, and green. Trees should be spaced to allow a minimum of ten feet clearance from the structure at full maturity.

The Home Protection Zone should be designed to promote fire-wise landscaping and water conservation, starting with low-density planting to medium density as you move outward from the house. The goal is to create a low-ignition landscape capable of slowing down fire spread. Plants that are green and lush give better protection. If regularly watered and pruned to remove dead or unhealthy material, these plants will be far less likely to carry fire to the home. While all plants will eventually burn, healthy ones with a high moisture content are more difficult to ignite.

Fire-wise landscapes should also include hardscape, such as granite paths and stone walls. These can act as a fuel break in between islands of native vegetation and help to slow or change the path of an approaching fire.

The Home Protection Zone should be designed to prevent ignition and slow down fire spread. ©Resource Conservation District of the Santa Monica Mountains

Zone 2: Reduced Fuel and Thinning

The Reduced Fuel and Thinning Zone has a dual function. It serves as a connection with the natural environment, promoting habitat restoration while eliminating continuous, dense vegetation, to decrease the energy and speed of the wildfire. This zone supports habitat connectivity and wildfire discontinuity. We advise not to remove vegetation down to bare soil, nor to destabilize hillsides by using heavy equipment that could result in soil erosion and mudslides.

The Reduced Fuel and Thinning Zone supports habitat connectivity and wildfire discontinuity. ©Resource Conservation District of the Santa Monica Mountains

The surrounding wildland

Continued habitat loss and fragmentation threaten the long-term existence of many native species and pose the greatest threats to biodiversity. These threats remain acute in Southern California and specifically in urban areas. One hundred and forty-nine plant and animal species that are rare, threatened, or endangered occur in the Santa Monica Mountains. As intact habitat is lost, the numbers of lost rare, threatened, and endangered species rise. These species contribute to biodiversity and serve extremely important roles in natural ecosystems.

Chaparral and coastal sage scrub are the predominant vegetation types in the Santa Monica Mountains. Together, they can produce extreme fire behavior, yet these plant communities are among the most ecologically significant in Southern California. They possess exceptional watershed value, including soil stabilization and groundwater recharge. The valuable viewscapes they create make the region a popular place to live and visit. They also provide crucial habitat to many declining species of wildlife.

Sticky monkey-flower (Diplacus aurantiacus), California poppy (Eschscholzia californica) and other native and drought tolerant perennials. © Saxon Holt/PhotoBotanic

The habitat value of a native garden

Native plants are essential ecosystem components and provide habitat for native birds, butterflies, and other wildlife. Other reasons to plant California natives in our gardens are to create a sense of place and for their beauty, adaptability, and drought-tolerant qualities. However, the most important reason to grow native plants is their value to the ecosystems that depend on them.

Suburban, urban, and rural gardens are quickly becoming the last refuge for many wild species, such as songbirds, butterflies, bees, toads, frogs, and other beneficial creatures that have lost habitat due to human development. In some cases, cultivated gardens with a rich diversity of native plants offer more resources, such as foraging opportunities for birds and other wildlife, than surrounding degraded wild lands.

Monarch butterfly @Janet Thatcher 2011

Which native plants are fire resistant?

Several factors influence the fire characteristics of plants, including plant moisture content, age, total volume, dead material, and chemical content. Plant lists can be misleading, giving the homeowner or landscape designer the impression that fire-safe landscaping is only about choosing the right species and avoiding the wrong ones. The reality is that landscape maintenance is essential. A well-maintained, irrigated ‘flammable’ plant can represent a lower ignition risk than a neglected fire-safe plant. Because any plant species can burn, we focus on the underlying principles behind designing a fire-safe home and landscape, and on maintaining structures and plants properly.

 

Fire-hazardous plants typically share certain characteristics:

  • Plants that are summer dormant unless being watered year round (e.g., sagebrush, sages)
  • Plants that produce dry leaf litter and duff that accumulates on top of the soil and on other plants in the vicinity
  • Trees and shrubs with dry, peeling bark
  • Trees and shrubs that retain clusters of dead leaves/branches/fronds (e.g., palms, eucalyptus, Italian cypress)
  • Dry grasses that grow green in the winter and turn yellow/brown in the summer

Plant characteristics diagram: flammability based on environmental and innate plant factors. ©Resource Conservation District of the Santa Monica Mountains Climate and fire circles

Plant characteristics and maintenance steps to reduce ignition risk:

The best plants have the following characteristics:

  • High-moisture plants that grow close to the ground (like succulents)
  • Plants with a low sap or resin content
  • Plants with high moisture content and flexible leaves
  • Plants with thick leaves
  • Plants without fragrance
  • Plants with silver or gray leaves
  • Plant leaves without noticeable hairs

Planning and maintenance considerations:

  • Water plants regularly to reduce dead leaves/duff production.
  • Remove dead branches and clusters of dead leaves from large, green trees and shrubs (e.g. coast live oaks that can act as a shield against flying embers).
  • Group plants by irrigation needs.
  • Space plants for mature size—plan ahead for maturity.
  • Work with the seasons. Autumn is the best time to plant native plants.

California Sycamores © Elisa Read

Wildfires will continue to shape the wildlands of the west. It is our responsibility to cohabitate with our fire ecology and to protect our wildlife and its native habitat. The comprehensive website defensiblespace.org is the first of its kind, combining wildfire safety and ecology for Southern California. Our goal is to improve both resource conservation and wildfire resistance by providing easy to follow maintenance practices for use by homeowners in their defensible space zone.

 


The Technical Advisory Committee for defensiblespace.org includes representatives from National Park Service, Los Angeles County Fire Department, Los Angeles County Department of Regional Planning, Ventura County Fire Department, California State Parks, Santa Monica Mountains Conservancy, Mountains Recreation & Conservation Authority, Mountains Restoration Trust, U.S. Geological Survey, University of California, California Native Plant Society, North Topanga Canyon Fire Safe Council, Theodore Payne Foundation, and TreePeople. Design partners included RIOS (content development and branding) and Persechini & Co. (web production).

     

The Guidance for Sustainable Defensible Space Landscaping in the SMMNRA and Southern California Program is part of California Climate Investments, a statewide program that puts billions of Cap-and-Trade dollars to work reducing GHG emissions, strengthening the economy, and improving public health and the environment– particularly in disadvantaged communities. The Cap-and-Trade program also creates a financial incentive for industries to invest in clean technologies and develop innovative ways to reduce pollution. California Climate Investments projects include affordable housing, renewable energy, public transportation, zero-emission vehicles, environmental restoration, more sustainable agriculture, recycling, and much more. At least 35 percent of these investments are located within and benefiting residents of disadvantaged communities, low-income communities, and low-income households across California. For more information, visit the California Climate Investments website at: www.caclimateinvestments.ca.gov.