Effects of wild land fuel treatments located in the Highway 50 corridor in El Dorado County on future wildfire size and severity, greenhouse gas emissions and carbon storage

SIG worked with California’s El Dorado and Georgetown Divide Resource Conservation Districts to estimate potential reductions in greenhouse gas (GHG) emissions and future carbon sequestration from several wildland fuel treatment projects in the Highway 50 corridor in El Dorado County. 

The projects are part of the Fire Adapted 50 (FA50) and South Fork American River Cohesive Strategy (SOFAR), which is a collaboration involving the RCDs, Cal Fire, U.S. Forest Service, Sierra Nevada Conservancy, and other entities. The fireshed analyzed covers 492,307 acres.

Results show clear benefits from fire treatments, including a reduced risk of high-severity wildfire. Such fires in the area are especially damaging because they can result in a change in vegetation type from forest to shrub—a complete loss of live tree biomass for at least 20 years, which comes at a high cost of forgone carbon sequestration. 

Treatments also show benefits in terms of a reduced conditional burn probability, not only in the treated areas but also in adjacent downwind stands, a phenomenon known as the treatment shadow effect. 

Assuming that the project areas all encounter wildfires during the 40-year analysis period, all of the treatments show GHG emission benefits, with an impact in saved GHG emissions of about 20 metric tonnes of carbon dioxide equivalent per fireshed acre, compared to a no-treatment baseline. If GHG emission benefits are discounted by applying a statistical estimate of annual wildfire probability, the results are different. Under the statistical estimate used in the study, there is no net reduction in GHG emissions over the analysis period because the GHG emissions associated with removal of vegetation for fire treatments is not fully offset by future sequestration, reduced emissions from future wildfires, or reduced likelihood of converting forest to shrubland. 

In summary, the study showed that fire treatments have benefits in terms of changing wildfire behavior within and beyond treated stands. Although the study showed no net reduction in GHG emissions, that finding is largely a result of the assumption of annual fire probability. If the probability of wildfire in the future is greater than the statistical probability used in this study, then the treatment projects will result in reduced GHG emissions. Given the fire history in the SOFAR watershed, it is reasonable to expect future fires to occur more frequently than estimated in this study—and therefore a greater likelihood that the treatments will lead to reduced GHG emissions in the future.