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Effects of wildfire on aquatic habitat in the area of the Northwest Forest Plan
Citation:
Ebersole, J., R. Flitcroft, C. Hirsch, M. Snyder, AND S. Wall. Effects of wildfire on aquatic habitat in the area of the Northwest Forest Plan. Oregon Post-Fire Research and Monitoring Symposium, Corvallis, OR, February 07 - 08, 2023.
Impact/Purpose:
Wildfires are a growing threat to water supplies, aquatic habitat, and human infrastructure, particularly in western North America. Wildfires can adversely impact aquatic habitat, for example by increasing fine sediment loads to streams, and can also help create habitat beneficial for sensitive aquatic species, for example by contributing large wood structure to streams. Data on stream habitat and macroinvertebrate assemblages have been collected by the US Forest Service for 20 years from sites across western Washington, Oregon, and California, largely on federal forest lands. A surprisingly high proportion (54%) of sites have experienced a wildfire at least once during this 20 year period. This research utilizes monitoring data to evaluate changes in aquatic habitat following wildfire. This will help inform our understanding of how and when wildfires impact aquatic habitat in both negative and positive ways.
Description:
The effect of wildfire on aquatic habitat over time is not well understood due to the absence of systematic observations over long periods of time. In Western Oregon, Washington and Northern California, the Aquatic and Riparian Effectiveness Monitoring Program (AREMP) has been collecting ongoing monitoring data to support management of forest lands under the Northwest Forest Plan (NWFP) (a plan covering ~99,000 km2 / 24.5 million acres). Data collection for this program began in 2002 and includes 261 randomly selected watersheds with at least 25% federal ownership that are surveyed on an approximately 8-year return interval. During the operating time-period of this monitoring program, increases in the intensity and severity of wildfires has occurred throughout western states. Due to the extensive distribution of watersheds, and consistent sampling intensity and methodology of the field survey program, about half of the watersheds sampled by AREMP have burned due to wildfire since 1988. This project analyzes the extensive pre and post-wildfire data collected by the AREMP program to allow comparisons among ecoregions, wildfire intensities, and burn extents on in-stream aquatic habitat with a special focus on post 2020 Cascade Range wildfire effects. We have found extensive entry of wildfire into forest lands throughout the range of the NWFP. Of the 261 total AREMP watersheds, 142 (54%) have burned at least once since 1984, and of these, 81 have experienced multiple wildfires. Patterns of aquatic habitat and habitat change vary by ecoregion and stand composition. Further analysis will explore the role of stand age, wildfire return interval, high intensity precipitation events, and time since wildfire to better capture the response of aquatic habitat to wildfire. The views expressed in this poster are those of the author(s) and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency or U.S. Forest Service.