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To Burn or Not to Burn: An Empirical Assessment of the Impacts of Wildfires and Prescribed Fires on Trace Element Concentrations in Western US Streams
Citation:
Beyene, M., S. Leibowitz, C. Dunn, AND K. Bladon. To Burn or Not to Burn: An Empirical Assessment of the Impacts of Wildfires and Prescribed Fires on Trace Element Concentrations in Western US Streams. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 863(10):160731, (2023). https://doi.org/10.1016/j.scitotenv.2022.160731
Impact/Purpose:
Increases in trace element concentrations in water bodies is of great concern for the health of humans and aquatic organisms because of their prolonged environmental residence time (10 - 100 years), high toxicity, and potential to bioaccumulate in the food web. In recent decades, the area burned, burned severity, and length of the wildfire season have increased in many parts of the world, increasing concerns about the immediate and long-term effects on trace element concentrations and other water quality parameters. In the meantime, the use of low severity prescribed (or controlled) fires in forested environments has increasingly been advocated as an effective tool to mitigate the likelihood and impact of large-scale wildfires. Information is lacking in the literature, however, on the trace element concentration effects of prescribed fires relative to that of wildfires. In this study, we assessed the effects of 54 wildfires and 11 prescribed fires on trace element (arsenic, selenium, and cadmium) concentrations of streams draining burned watersheds in the western US. Our study differs from previous studies in the following critical ways. This is the first empirical study that compared the water quality effects of prescribed fires vs. wildfires. Unlike previous studies that are based on individual fires, this study also assessed multiple stream sites to broadly characterize wildland fire impacts on trace elements concentration of western US streams. Moreover, more than one analytical approach for detecting fire effects was used here to reduce uncertainty in our findings stemming from scarcity of temporal constituent concentration data. Only a handful of wildfire studies have utilized multiple analytical methods to infer fire effects on water quality. For the first time, our study conducted a thought experiment where the post-fire trace element concentration changes were estimated if prescribed fires reduced the size and severity of historical wildfires. Our results indicated that large, high severity wildfires can raise the trace element concentration of streams for the following three years. Conversely, prescribed fires were rarely related to increases in trace element concentrations. Results also demonstrated that the post-fire trace element response in streams was primarily influenced by burn area, burn severity, post-fire weather, surface lithology, watershed physiography, and land cover. This study could ultimately lead to a better understanding of the potential water quality improvements if prescribed fires were applied to reduce the size and severity of subsequent wildfires. This research is a component of AE 8.2.3 “Models of wildfire effects on stream and lake water quality”.
Description:
The use of low-severity prescribed fires has been increasingly promoted to reduce the impacts from high-severity wildfires and maintain ecosystem resilience. However, the effects of prescribed fires on water quality have rarely been evaluated relative to the effects of wildfires. In this study, we assessed the effects of 54 wildfires and 11 prescribed fires on trace element (arsenic, selenium, and cadmium) concentrations of streams draining burned watersheds in the western US. To obtain results independent of the choice of method, we employed three independent analytical approaches to evaluate fire effects on water quality for the first three post-fire years. In general, we observed significant increases in trace element concentrations in streams burned by large, high-severity wildfires, despite substantial variability across sites. Comparatively, we did not observe increases in the spring mean concentration of arsenic, selenium, and cadmium in watersheds burned by prescribed fires. Our analysis indicated that the post-fire trace element response in streams was primarily influenced by burn area, burn severity, post-fire weather, surface lithology, watershed physiography, and land cover. Results of our analysis demonstrate that prescribed burns could reduce the post-fire trace element loads in downstream waters if prescribed fires reduce subsequent high severity fires in the landscape.
URLs/Downloads:
DOI: To Burn or Not to Burn: An Empirical Assessment of the Impacts of Wildfires and Prescribed Fires on Trace Element Concentrations in Western US Streams