A defensible space, in the context of fire control, is a natural or landscaped area around a structure that has been maintained and designed to reduce fire danger. The practice is sometimes called firescaping. "Defensible space" is also used in the context of

wildfire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

s, especially in the wildland-urban interface (WUI). This defensible space reduces the risk that fire will spread from one area to another, or to a structure, and provides

firefighter A firefighter (or fire fighter or fireman) is a first responder trained in specific emergency response such as firefighting, primarily to control and extinguish fires and respond to emergencies such as hazardous material incidents, medical in ...

s access and a safer area from which to defend a threatened area. Firefighters sometimes do not attempt to protect structures without adequate defensible space, as it is less safe and less likely to succeed.

Criteria

*A first concept of defensible space for most fire agencies' primary goal of fuel reduction is a recommended or required defensible space around a structure to extend for at least in all directions. *A second concept of defensible space is "fuel reduction." This means plants are selectively thinned and pruned to reduce the combustible fuel mass of the remaining plants. The goal is to break up the more continuous and dense uninterrupted layer of vegetation. *A third concept of defensible space is " fuel ladder" management. Like rungs on a ladder, vegetation can be present at varying heights from groundcover to trees. Ground fuel "rungs", such as dried grasses, can transmit fire to shrub rungs, which then transmit up tree branch rungs into the tree canopy. A burning tree produces embers that can blow to new areas, spreading and making it more difficult to control a wildland fire. One guideline is for a typical separation of three times the height of the lower fuel to the next fuel ladder. For example, a shrub under a tree would need a spacing of to the lowest limbs of the tree. Since wildfires burn faster uphill than on flat land, fuel ladder spacing may need to be greater for slopes.

Landscape use

The term defensible space in landscape use ("firescape") refers to the zone surrounding a structure. Often the location is in the

wildland–urban interface The wildland–urban interface (WUI) is a zone of transition between wilderness (unoccupied land) and land development, land developed by human impact on the environment, human activity – an area where a built environment meets or intermingles ...

. This area need not be devoid of vegetation by using naturally fire resistive plants that are spaced, pruned and trimmed, and irrigated, to minimize the fuel mass available to ignite and also to hamper the spread of a fire. #The first is the "Defensible Space Zone," of a defensible space around a structure. It is where

vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...

is kept to a minimum combustible mass. A guideline used in this zone can be "low, lean and green." Trees should be kept to a minimum of from other trees to reduce risk of fire spread between trees. Wood piles should be kept in zone 2. No branches should be touching or hanging over the roof of the house or within 10 feet of the structure to help keep the structure safe. Any dead vegetation or plants from zone 1 should be removed, and vegetation near windows should be pruned or removed. #The second distance of , is the "Reduced Fuel Zone" of a defensible space around a structure. In this area of the defensible space, fuels and vegetation are separated vertically and horizontally depending on the vegetation type. This is done by: thinning, pruning, and removal of selected vegetation; and removing lower limbs from trees closer to lower vegetation and the lateral separation of tree canopies. Grass height should not exceed . Trees should be 10 feet away from each other on a flat to mild slope but should be double that on a mild to moderate slope. Shrubs should be as far away as twice its height for flat to mid-slope but four times its height for mild to moderate slope. Leaves, twigs, needles, clones, bark, and small branches should be removed but can be left up to a depth of . Vertical space from trees to ground should be while the vertical distance from a tree to a shrub should be the height of the shrub times three. Creating zones to better divide the space is the recommended approach to having effective defensible space. These zones act as partitions to show what can be allowed in certain areas. There should be no dried vegetation or flammable materials near this zone. Zone 0 is anything 0-5 feet from the building. Gravel, pavers and noncombustible mulch should be used to create a barrier between the home and zone 1. Zone 1 is anything within 30 feet of the building. All combustibles should be removed from this zone. This includes dried vegetation, wooden furniture, umbrellas and canopies. Ideal substitutions for this zone would be well irrigated grass, rocks and metal furniture. Zone 2 should have well spaced out trees and other vegetation. Noncombustible furniture and structures should be separating the flammable vegetation. Fire breaks such as gravel pathways and driveways should be used as fire breaks on the property. Grass should be well irrigated and cut regularly. There should be enough vertical space between trees and ground vegetation to prevent fire spread. Zone 3 is the transition zone between the defensible space and the natural land. Maintenance is not as strict bust should still be done. The main goal of this zone is to slow the speed of the fire and keep it from spreading to the other zones. An important component is ongoing maintenance of the fire-resistant landscaping for reduced fuel loads and fire fighting access. Fire-resistive plants that are not maintained can desiccate, die, or amass deadwood debris, and become fire assistive. Irrigation systems and pruning can help maintain a plant's fire resistance. Maintaining access roads and driveways clear of side and low-hanging vegetation can allow large fire equipment to reach properties and structures. Some agencies recommend clearing combustible vegetation at minimum horizontal from roads and driveways a vertical of above them. Considering the plant material involved is important to not create unintended consequences to habitat integrity and unnecessary aesthetic issues. Street signs, and homes clearly identified with the numerical address, assist access also.

Fire Resistant Plants

Some of the best ways to slow the spread of a fire to homes is to reduce the amount of fuel available for the fire. Within each zone, the amount of vegetation should drastically decrease. Having fire resistant plants in zones farther away form the home will help to slow down the fire even more. Some things to look for when picking fire resistant plants are high moisture content in leaves, limited dead vegetation, and low amounts of oils within the plant. Upkeep on these plants are also important for fire protection. Removal of excess branches and leaves will lessen the amount of potential fuel. Here are a few fire resistant plant examples, there are many different types of flowers, shrubs and trees that have fire resistant properties.

Unintended consequences

The unintended negative consequences of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and native

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

loss can result from some unskillful defensible space applications. The disturbance of the soil surface, such as garden soil cultivation in and firebreaks beyond native landscape zones areas, destroys the native plant cover and exposes open soil, accelerating

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

of plants ("invasive exotics") spreading and replacing native

s. In suburban and

areas, the vegetation clearance and brush removal ordinances of municipalities for defensible space can result in mistaken excessive

clearcutting Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with Shelterwood cutting, shelterwood and Seed tree, seed tree harvests, it is used by foresters t ...

of native and non-invasive introduced shrubs and perennials that exposes the soil to more light and less competition for invasive plant species, and also to erosion and landslides. Negative aesthetic consequences to natural and landscaped areas can be minimized with integrated and balanced defensible space practices.USA (1999). Executive Order 13112 of February 3, 1999: Invasive Species. Federal Register 64(25), 6183-6186.

References

External links

CAL-FIRE: Homepage + Links
Official CA State Board of Forestry and Fire Protection website.
CA State Board of Forestry and Fire Protection: "General Guidelines for Creating Defensible Space"
Official Santa Barbara County Fire Department 'Wildfire' Website.
Santa Barbara County Fire Department: "Landscape Checklist"
{{Horticulture and Gardening Wildfire prevention Wildfire suppression Gardening aids Sustainable forest management