LB 18-165 - Online Mapping Tool to Quantify Wildfire Impacts in Carbon Storage and Other Ecosystem Services in California’s Shrublands

Shrublands characterize the world’s Mediterranean-type climate regions. In southern California they are the most extensive ecosystem and dominate the four southern USDA Forest Service National Forests. Wildfire is a natural disturbance in California’s shrublands and critical for its healthy functioning. However, a rise in anthropogenic ignitions has resulted in increased fire frequency, which is having disastrous effects on property and human lives and incurring millions of dollars in suppression costs. Less obvious, though, are the intangible environmental impacts of wildfires – the consequences on the provision of ecosystem services, such as carbon storage, to the millions of people who live in close proximity. We developed a method to estimate aboveground live chaparral biomass using the deep temporal record of Landsat imagery and annual precipitation as time-dependent predictors. We used Random Forest, an ensemble machine-learning algorithm to build an aboveground live biomass model using over 700 field plots from several sources. Based on these aboveground live biomass estimates (2000-2021) we then estimated standing dead, litter, and belowground shrub biomass pools. Results showed mean biomass for the southern California ecoregion and percent uncertainty for each of the pools as: AGLBM (905.4 g/m2, 14.4%); standing dead (644.9 g/m2, 1.3 %); litter (731.2 g/m2, 1.2 %); and belowground (776.2 g/m2, 17.2 %). To allow resource managers to access data on ecosystem services, we created a web mapping tool, SoCal EcoServe, to quantify fire impacts on six ecosystem services: carbon storage, water runoff and groundwater recharge, sediment erosion, recreation, and biodiversity. We illustrate the outputs of EcoServe using the Bobcat Fire on the Angeles National Forest: water runoff and recharge increased by 20,000 and 17,000 acre/feet per year respectively; sediment erosion increased eight times; and carbon storage decreased immediately post-fire by 166,000 metric tons. We also estimated that 1.2% of shrub biomass would not recover over the long-term based on fire frequency and time since last fire. Quantifying the impacts of wildfire on ecosystem services in addition to routine fire suppression expenses is increasingly recognized as an important component of natural resource management on public lands in southern California. In addition, assessing areas of high ecosystem service provision can help prioritize areas for post-fire management activities, such as restoration to stabilize slopes in areas of high erosion risk.