Session: : Effects Of Multiple Global Changes On Communities And Ecosystems 2
COS 82-2 - Debris flows triggered by wildfires and subsequent extreme weather events generate dramatic changes to rocky intertidal marine ecosystems, using endangered black abalone as a case study
PhD Candidate University of California, Santa Cruz, United States
Abstract: The black abalone (Haliotis cracherodii) is a critically endangered species found on the west coast of North America from roughly San Francisco, California to Baja California, Mexico. While overfishing contributed to its decline, withering syndrome decimated populations, especially in central and southern California, beginning in the 1980’s. Many areas south of the Big Sur coast have experienced declines of 90% or more. Since a leveling off of withering syndrome deaths, it was hoped the species would recover by expanding from its last remaining stronghold populations in central California. However, in 2020/2021, a fire + flood event precipitated numerous debris flows that buried hundreds of meters of Big Sur coast’s rocky intertidal habitat and “healthy” black abalone populations. Our team surveyed black abalone populations and rocky intertidal habitat before and after debris flows and recorded impacts severe enough to warrant rescue/relocation efforts, which we conducted in 2021. We have since been quantifying the initial and ongoing impacts of this natural disaster through on-site surveys and the use of drone imagery. The losses documented for black abalone serve as an example of broader impacts to the rocky intertidal ecosystem and also hint at possible subtidal effects. This case study may be one of an increasing number of impacts to coastal systems from post-fire debris flows given climate change predictions for California and other areas around the world including increasing (1) fire intensity and frequency, (2) drought conditions that reduce vegetative cover, and (2) risk of severe flooding from extreme storms, such as atmospheric rivers.
