RSS FeedsFire Ecology
This chapter focuses on the ecological role of fire in the County’s biotic communities. The purpose of this chapter is to establish baseline data that will allow for the analysis of impacts on biological resources due to changes in the fire regime as the population of the County increases, development patterns change, and decisions and policies are considered regarding fuel management.
 California native grasslands have been identified as one of the most endangered ecosystems in the United States, so it is important to carefully consider the effects of fire on this grassland assemblage. |
Fire suppression over the last 50 to 100 years has resulted in a decrease in fire frequency in many of the County’s biotic communities. The reduction in fire frequency has likely led to declines in some special-status species that are favored by fires, and the degradation of some sensitive communities. Serpentine grassland is an example of one such sensitive community, which has undergone invasion by barbed goatgrass (Aegilops triuncalis), a fire-intolerant noxious weed. There are two principal mechanisms by which fire suppression threatens the County’s biotic communities and special-status species: increased dominance by less fire-tolerant species, and increased probability of severe standreplacing fires.
In some communities, the reduction in fire frequency has led to a buildup in fuels (biomass) such as woody shrubs and downed wood. Increased fuel loads have increased the probability of extensive and severe fires. Such fires have the potential to cause the loss of sensitive communities such as oldgrowth Douglas-fir–ponderosa pine forest, which would lead to declines in special-status species such as the northern spotted owl (Strix occidentalis caurina) that are dependent on this habitat.
The probability of extensive stand-replacing fires in many biotic communities in the County is increased by the spread of human development adjacent to natural areas. Increasing human development (including roads) is correlated with the frequency of wildfire ignitions. In contrast, agricultural development adjacent to natural areas has reduced the probability of extensive and severe fires in some areas. Vineyards have lower fuel loads than biotic communities such as oak woodlands, chaparral, and coniferous forest.
Most of the County’s biotic communities are at moderate risk of losing key ecosystem components due to changes in the fire regime. These communities include non-native grasslands, xeric and mesic chaparral, and some areas of riparian woodland, oak woodland, and coniferous forest. Significant portions of the County’s oak woodlands and coniferous forests are at high risk of degradation or type conversion due to the increased probability of severe fire.
There is also a strong need for better local and regional land use planning to slow or halt the increase in fire risk as the population increases and development spreads. Such planning is particularly important for the wildland urban interface, where developed areas and wildlands meet and where extensive property damage and loss of life from fire is typically concentrated (California Department of Forestry and Fire Protection 2000).
As the County population continues to grow, local, state, and federal agencies charged with biodiversity conservation and fire protection will continue to struggle with increased sources of ignition, the demand for increased fire suppression, and the concomitant changes in fire regime that accompany a growing population and continuing development. This report takes an initial step to assess and address fire management needs in the context of local land use planning in Napa County.
