Pacific Southwest

Title: Development and fire trends in oak woodlands of the northwestern Sierra Nevada foothills

Author: Spero, James G.

Date: 2002

Source: In: Standiford, Richard B., et al, tech. editor. Proceedings of the Fifth Symposium on Oak Woodlands: Oaks in California's Challenging Landscape. Gen. Tech. Rep. PSW-GTR-184, Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 287-301

Station ID: GTR-PSW-184

Description: Human development appears to present a larger threat to the long-term persistence of California's hardwood rangelands than fire in terms of likely ecological significance. This paper describes of the California Department of Forestry and Fire Protection's Fire and Resource Assessment Program (FRAP) projections of human development and fire occurrence and explores trends in the incidence of fire and development on woodland areas historically dominated by oak species. Previous FRAP work on fire probability on about 3 million acres of private lands in the northwestern Sierra Nevada foothills provides a small-scale model of comparison for these forecasts. FRAP's methods combine historical (1950-1990) block group housing density estimates based on the 1990 Census with decadal housing projections (2000-2040) derived from Department of Finance county population projections. County housing projections are allocated to 9.6 square mile grid cells based on their share of county housing growth between 1980 and 1990. The primary purpose is to produce estimates with a low level of error in the acreage that is projected to attain at least a dispersed level of residential land use. Overlaying development projections on a 1945-vintage vegetation map yields tables of vegetated acres developed from 1950 to 2040. In this analysis, developed areas are defined as having reached a housing density of at least one house per 20 acres and presumed to present a potential for ecological impact. Current and future "footprints" of development within the study area are compared to the expected amount of fire over time to provide a context for evaluating the ecological significance of development and fire in hardwood ecosystems. By 2040, an estimated 507,000 acres (22 percent of the ~2.3 million acres of 1945-era oak woodland in the study area) will be developed. This regional rate of development is higher than for all oak woodlands statewide, which show 16 percent development by 2040. In the study area, hardwoods burned on the average ~0.5 percent per year where development density was less than one house per 20 acres. In areas of higher development density, the rate of burning was about 0.2 percent. An estimated 411,812 acres will burn in the 2000-2040 period. Driving this estimate are area characteristics, such as predominating vegetation life form and developed/undeveloped status. Plausible reasons for reduced fire occurrence in developed areas include quicker detection, more fire suppression resources, improved access and fire safe development, and modified vegetation composition and structure that lessens fire hazard. Assuming 30 percent and 5 percent net mortality from development and fire, respectively, FRAP researchers estimate that by 2040, about 80,000 acres (about 4 percent of the vegetation extant in 2000) might be lost due to development (about 60,000 acres from development, about 20,000 acres from fire). Long-term ecological impacts are perhaps more permanent with development than with fire, however, both fire suppression and land development policies will help shape the future of quickly developing foothill ecosystems. This analysis is a work in progress by the author and FRAP. Conclusions, data, and discussion are those of the author and FRAP.

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Citation

Spero, James G.  2002.  Development and fire trends in oak woodlands of the northwestern Sierra Nevada foothills.   In: Standiford, Richard B., et al, tech. editor. Proceedings of the Fifth Symposium on Oak Woodlands: Oaks in California's Challenging Landscape. Gen. Tech. Rep. PSW-GTR-184, Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 287-301.