Fire and management history limit the likelihood and severity of subsequent forest fires in California

Authors: Jonathan Wang*, University of California, Irvine, Clarke Knight, University of California, Berkeley, John Battles, University of California, Berkeley, Michael Goulden, University of California, Irvine, James T Randerson, University of California, Irvine
Topics: Hazards and Vulnerability, Remote Sensing, Mountain Environments
Keywords: fire, remote sensing, big data, time series, California
Session Type: Virtual Paper
Day: 4/7/2021
Start / End Time: 3:05 PM / 4:20 PM
Room: Virtual 7
Presentation File: No File Uploaded

Climate change is amplifying the fire regime of California, threatening its natural resources and motivating policies that reduce the risk of catastrophic wildfires. Because California climate change policy includes the protection of forests and shrublands, it is essential to characterize the degree to which forest management practices and recent fire history reduce the likelihood and severity of future fires. However, current records of disturbance can be coarse and incomplete, making it challenging to assess these feedbacks. To address this, we developed a state-wide map of land disturbances using time series of Landsat remote sensing data. We applied the Continuous Change Detection and Classification (CCDC) algorithm to all Landsat pixels to build annual (1984 – 2019) maps of disturbance incidents and severity at 30 m spatial resolution. We then trained a Random Forest algorithm on the intersection of a sample of 122,533 CCDC-derived breaks with existing archival databases of fire, forest management, and insect-induced mortality to predict disturbance types with an overall accuracy of 85.6%. Fires afflicted the largest area (15,272 km2), followed by harvest (12,723 km2) and die-off (1,223 km2). A history of past fire and forest management inoculated areas from future fires, with recently disturbed (e.g. within 10 years) areas burned much less frequently than the background rate of burn and considerably less severe fires for up to fifteen years post fire. Our results suggest that forest management practices may help protect Californian forests from future catastrophic wildfires for up to two decades.

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