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Published on: November 14, 2017
Human influence on California fire regimes.
Alexandra D Syphard1, Volker C Radeloff, Jon E Keeley
1Department of Forest Ecology and Management, University of Wisconsin, Madison, Wisconsin 53706, USA. asyphard@yahoo.com
Summary
Human activity, particularly housing density and development patterns in wildland-urban interfaces (WUI), significantly influences wildfire frequency and area burned in California. Fire risk is highest at intermediate human activity levels, not just at the wildland-urban interface.
Area of Science:
- Ecology
- Environmental Science
- Conservation Biology
Background:
- Periodic wildfires are crucial for maintaining California's mediterranean-climate shrublands.
- Human activities, especially at the wildland-urban interface (WUI), are altering natural fire regimes and increasing ecological risks.
- Current fire risk assessments often overlook the influence of human factors, relying primarily on biophysical variables.
Purpose of the Study:
- To investigate the influence of human activities on wildfire occurrence and extent in California.
- To determine if the relationship between human factors and fire is linear or nonlinear.
- To assess the effectiveness of human variables in predicting contemporary and historical fire data.
Main Methods:
- Collected contemporary (2000) and historical (1960-2000) fire data for California.
- Developed fine-resolution maps of the wildland-urban interface (WUI) using housing density and land cover data.
- Analyzed relationships between fire data and human variables (WUI types, population density, road density, distance to WUI) and biophysical variables using regression analyses.
Main Results:
- Human variables, especially population density, intermix WUI, and distance to WUI, significantly explained fire frequency (R2 = 0.72) and area burned (R2 = 0.50).
- Nonlinear relationships were observed, with fire frequency and area burned peaking at intermediate levels of human activity.
- Human activities also explained changes in fire over time, with greater explanatory power in earlier periods (1960-1980).
Conclusions:
- The spatial arrangement of human development is a critical factor in understanding and predicting wildfire risk.
- Land use planning considering specific housing density thresholds can help mitigate fire risk.
- Continued development in wildland areas poses significant ecological risks due to increased fire proximity to human infrastructure.
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