Spatial Scale and Hazard Perception: An Exploratory Analysis

Abstract

This study tests the relationship between spatial scale and hazard perception, accounting for selected sociodemographic and property-related factors. Results reveal significant relationships between spatial scale and wildfire hazard perceptions of survey respondents from Arizona's White Mountains. Hazard perception increased across four ascending spatial scalar levels (from home structure to community levels). Relationships between two (of eight) variables (property landscape hazard exposure, ecological knowledge) and hazard perception were significant when ignoring spatial scale; when accounting for spatial scale, however, significant relationships registered at specific levels for seven variables (home ignitability, property landscape hazard exposure, mitigation, property value, housing tenure, full-time/part-time residency, ecological knowledge). Residents with lower (vs. higher) home ignitability, residents of higher (vs. lower) value properties, and owner-occupants (vs. renters) had significantly lower hazard perceptions at the home structure level and higher hazard perceptions at the community level. Findings are novel to risk perception research and have important implications.

Keywords:

• forest
• hazard
• mitigation
• risk perception
• spatial scale
• U.S. West
• wildfire
• wildland–urban interface

Acknowledgments

I thank Sara Grineski, Troy Hall, and the anonymous referees for their constructive comments and suggestions on drafts culminating in the completion of this article. Those who made the field component of this research possible must be recognized, including Sue Sisson, and members of the Natural Resources Working Group and the White Mountain Stewardship Project Multi-Party Community Monitoring Board. I am also thankful for the financial support that I received in support of this work. The article stems from research funded by a Mathew G. Bailey Scholarship, a Graduate and Professional Student Association Dissertation Research Grant, a Millennium Interdisciplinary Dissertation Fellowship, and a National Science Foundation Integrative Graduate Education and Research Training in Urban Ecology Fellowship, all through Arizona State University; an Association of American Geographers Dissertation Research Grant; and the City of Show Low, Arizona. All errors and omissions are my own.

Notes

^a A = strucutred household survey; B = Navajo County, Arizona parcel data; C = in-field property assessment.

The survey instrument focused entirely on forests and fuels as the cause of “fire hazard” (and forest/fuel management, e.g., property fuel hazard mitigation, as the means to reduce fire hazards). The survey did not include any focus on ignition as a cause of “fire hazard.” The term “hazard” was used instead of “risk” throughout the survey to minimize the potential for respondents associating “risk” with the probability of fires occurring (which would possibly have led them to estimate “risk” as higher at progressively broader scales).

The survey instrument defined “neighborhood” as being “less than ½ mile from your house” and “community” as being the “town where you live.”

“Home ignitability” equally weights two measures developed for the home structure and the defensible space. Home structure hazard is the sum of ignitability measures for roof (1), structural setback (1), siding (1), decks (1), eaves (1), windows (1), skylights (1), and window exposure extent (1). Defensible space hazard is the sum of exposure measures for roof vegetation (1) and roof debris (1), chimney vegetation (1), deck vegetation (1), 0.6-m perimeter flammability (1), 3-m surface perimeter flammability (1), near home landscaping (2), 3-m home perimeter flammable tree presence (1), and isolation from forest canopy (1). “Property landscape wildfire hazard” is the sum of crown fire potential measures for number of flammable trees/acres (<30 = 0, 30.01–60 = 1, 60.01–100 = 2, 100.01–200 = 3, >200.01 = 4), crown closure (1), branches below 3 vertical meters (1), small tree ladders (1), accumulation of dead branches and downed trees (1), surface fuel connectivity (1), dead, diseased and damaged trees (1), surface-canopy ladders (1), grass near flammable materials (1), 8 + inches landscape grass height (1), vegetation (de)hydration (1), and 1 inch + surface pine needle accumulation (1).

The specific adjustments summed to create the “mitigation” measure correspond to hazards associated with: the home structure (remodeling exterior walls = 1, remodeling roof = 1, removing/rebuilding decks = 1, and installing dual-paned windows = 1); the defensible space (moving combustibles = 1, clearing flammable vegetation within a 3-meter perimeter = 1, regularly removing pine needles from roof = 1, and regularly raking most pine needles = 1); the property landscape (regularly trimming trees = 1, regularly watering trees = 1, removing trees = 1, re-landscaping with fire-safe plants = 1, and regularly mowing grass = 1); and fire suppression (maintaining an easily accessible driveway = 1, an easily identifiable address = 1, and a water supply for fire-fighting purposes = 1).

Mitigation and hazard exposure are independent measures. The correlation between home ignitability and mitigation is statistically significant, but weak (corr. = −.200 for the continuous variables and −.182 for the dichotomous variables used in analyses). The correlation between property landscape hazard and mitigation is not significant (corr. = −.069 for the continuous variables and −.026 for the dichotomous variables used in analyses).

Respondents were asked to provide true/false responses to the following statements (in “true” form): “restoration reduces fire hazard”; “ponderosa pine forests are fire-dependent”; “prescribed fire is a restoration tool”; “restoration benefits wildlife”; “restoration helps reestablish native plants”; “large fires result in part from fire suppression”; and “removing most pine needles reduces fire hazard.” Next, responses were converted to correct/incorrect and ecological knowledge scores (number correct/number of questions) were calculated. Results were then dichotomized into less vs. more ecological knowledge based on failing (<60% correct) vs. passing (≥60% correct) scores.

Mauchly's test indicated that the assumption of sphericity was violated, χ ² (5) = 216.23, p < .001; therefore, degrees of freedom were corrected using Huynh–Feldt estimates of sphericity (ϵ = .79).

Likewise, results of each of the two-way mixed-design ANOVA tests yielded significant results for the main effect of spatial scale on hazard perception, F(2.38–2.42, 1175.69–1211.10) = 125.37–295.21, all p values <.001. In each case, Mauchly's test indicated that the assumption of sphericity was violated; thus, degrees of freedom were corrected using Huynh–Feldt estimates of sphericity.