Introduction 

Wildland-urban interface communities across Nevada have programs in place to encourage homeowners to voluntarily undertake investments to reduce their wildfire threat (hereafter fire-safe investments) and create defensible space on their properties. This study addresses two questions relevant to the design of these programs.

First, are homeowners’ decisions to undertake fire-safe investments driven primarily by the perceived benefits of investment in terms of reducing the risk of their homes being destroyed in a wildfire (hereafter their wildfire risk) or by concerns about the cost of investment (financial costs and losses in landscape aesthetics and privacy)?  Answering this question will help those conducting community programs decide whether they should focus on (1) educating homeowners about the risk reduction benefits of fire-safe investment or (2) reducing homeowners’ cost of investment through subsidies or cost-sharing programs.

Second, are the factors that drive homeowners’ decisions to create defensible space on their property, which is the product of several individual investments, different from the factors that drive their decisions to make any individual fire-safe investment? Answering this question is important because, while the previous social science literature has focused on understanding homeowners’ decisions to spend either time or money reducing their wildfire risk, fire science research indicates that performing the full suite of fire-safe investments required for defensible space is the most effective way to increase the likelihood that a home will survive a wildfire intact (Cohen 2000). For this reason, community programs often focus on defensible space compliance. 

Data

We use data on homeowners’ fire-safe investments and defensible space compliance from 35 wildland-urban interface communities in Nevada.  The data set combines homeowner information from a mail survey with their observed fire-safe investments obtained through parcel-level hazard assessments. A total of 8,867 homes received hazard assessments. Mail surveys were sent to a random sample of 2,225 of these homes. From the 678 returned completed surveys (30.5% response rate), we dropped respondents who rented their home and with missing observations for key variables, to arrive at a final sample of 417 homeowners. The 35 communities were selected because prior work identified them as having an elevated wildfire hazard and ignition risk. Figure 1 depicts the location of the 35 communities in Nevada. 

Results

Eighty percent of the homeowners who answered the survey had spent either time or money (or both) reducing wildfire risk in the previous year, while only 36% of the sample had adequate defensible space.  Defensible space compliance is higher (46%) for homeowners who did not perform any fire-safe investments in the previous year than for homeowners who did (34%). The likely reason for this is that homeowner’s defensible space status is a result of their entire history of fire-safe investments, in addition to the fire-safe investments included in the purchase/construction of their homes. As such, homeowners can have adequate defensible space on their property without having undertaken a single investment in the previous year.

Table 2 reports the results on what determines homeowners’ fire-safe investment and defensible space decisions. Table 2 shows that homeowners’ decisions to create defensible space are driven by two variables that are correlated with their cost of investment: (1) the age of their home – older homes are more likely to use older, noncompliant building materials and tend to have mature landscaping; and (2) a concern about reduced privacy. Conversely, homeowners’ decisions to devote time or money to reducing wildfire risk are determined primarily by their perception of their wildfire risk. 

Management Implications

• Education programs that emphasize homeowners’ wildfire risk are likely to increase homeowners’ fire-safe investment by increasing their perceived benefits.
• Increasing defensible space compliance may require additional programs targeting homeowners’ cost of investment through subsidies or cost-sharing programs.
• Programs to encourage defensible space should focus on reducing the cost for homeowners in older homes who are more likely to have older, noncompliant building materials and mature landscaping.
• Education programs to encourage defensible space should emphasize strategies for homeowners to achieve compliance while still maintaining privacy from their neighbors.
• Defensible space compliance requires sustained investment and maintenance over time. Education programs should emphasize that defensible space is often an ongoing process rather than a one-time investment.

Citations

Sisante, Angelo M., Michael H. Taylor, and Kimberly S. Rollins. 2019. Understanding Homeowners' Decisions to Mitigate Wildfire Risk and Create Defensible Space. International Journal of Wildland Fire, 28: 901-911.

Cohen J.D. 2000. Preventing Disaster: Home Ignitability in the Wildland-Urban Interface. Journal of Forestry, 98: 15-21.

¹In wildland-urban interface wildfires, most residences are either undamaged or they are destroyed and require rebuilding; partial damage is relatively rare (Cohen 2000).

²The on-side hazard assessment determined whether each property had created defensible space in the 30-foot area surrounding the residence. Defensible space compliance required that the property had horizontal spacing between shrubs and trees, trees pruned up to 6 feet from the ground, no dead vegetation under decks or within 10 feet of the house, use of nonflammable landscaping materials and high moisture-content annuals and perennials to create a “fire-free” area within 5 feet of the residence, no firewood stacks or propane tanks in the fire free zone, and use of fire-resistant building materials.

Table 1. 35 Study Communities in Nevada by Predominant Vegetation

*For communities indicated with an asterisk, the U.S. Census Bureau does not provide individual population numbers. Aggregate populations are reported for:

1. Cold Springs, Red Rock, and Rancho Haven; 
2. Virginia City and Virginia Highland;
3.  Spring Valley and Topaz Lake;
4. Incline Village, Saddlehorn Tumbleweed, Tyrolian Village, Champagne Burgundy, Upper Tyner, and Allison Jennifer; and
5. Galena Forest and West Washoe Valley.

^RFor these communities, representative sections of the community were assessed.

Table 2. Determinants of Homeowner Defensible Space Compliance and Decision to Undertake Fire-safe Investment

Marginal effects evaluate at the mean of the independent variables. Marginal effects capture the percent change in the probability that a homeowner creates defensible space/makes a fire-safe investment with a one unit change in the independent variable.

Standard errors in parentheses.

*p<0.1, **p<0.05, ***p<0.01

¹See full paper for description of other covariates.

Published by: Taylor, M., Restaino, C., 2020, Understanding Homeowners’ Decisions to Mitigate Wildfire Risk and Create Defensible Space in Nevada, Extension | University of Nevada, Reno, FS-20-32

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