Wildfires and Climate

Science Center Objects

Over the last several decades, both the incidence of large wildfires and the duration of the wildfire season across much of the United States have increased (Westerling and others, 2006, American Water Works Assn, 2008; Finco and others, 2012). Future wildfire projections based on forecasted climate scenarios indicate both an increase in the expected severity of wildfires, and an expansion of wildfires over much of the northern hemisphere, particularly for western North America (Liu and others, 2010; Liu and others, 2012).

charred, bare trees on a mountain side

King Fire aftermath, Eldorado National Forest

While the conditions that contribute to the intensity, size, and duration of wildfires are complex, scientists generally agree that the occurrence of wildfires will increase with climate change (Batllori, E., Parisien, M.-A., Krawchuk, M. A. and Moritz, M. A., 2013). Warming trends, dry, drought-affected landscapes, and lower fuel moisture contribute to these affects. Studies have also linked climate change with post-fire coniferous tree mortality across the western United States, and – subsequently – an increase in wildfire fuel. This suggests a general – but often overlooked – relationship between climate and wildfire (van Mantgem, P.J., Nesmith, J.C.B., Keifer, M., Knapp, E.E., Flint, A., Flint, L., 2013).

Wildfire has many impacts on the hydrologic system and processes. Among these are changes in soil properties and removal of vegetation, both a result of fire intensity. Further, the potential loss of evapotranspiration from burned vegetation results in an increase in runoff as soil is no longer absorbing runoff water. The USGS studies the influence of fire on hydrologic systems using the Basin Characterization Model (BCM). This USGS modeling software allows scientists to use future climate and precipitation scenarios to calculate how much water may be able to be absorbed by soil, and how much may simply run off the land's surface.

The USGS and researchers at U.C. Berkeley are working together to better understand and assess the relationship between climate and wildfire in California using climate model scenarios. This research is part of wider efforts to develop real-time fire risk maps for California based on climatic stresses.