Wildfires increasingly impact western US fluvial networks

Wildfires are increasing globally in frequency, severity, and extent, but their impact on fluvial networks, and the resources they provide, remains unclear. We combine remote sensing of burn perimeter and severity, in-situ water quality monitoring, and longitudinal modeling to create the first large-scale, long-term estimates of stream-river length impacted by wildfire for the western US. We find that wildfires directly impact similar to 6% of the total stream+river length between 1984 and 2014, increasing at a rate of 342 km/year. When longitudinal propagation of water quality impacts is included, we estimate that wildfires affect similar to 11% of the total stream+river length. Our results indicate that wildfire activity is one of the largest drivers of aquatic impairment, though it is not routinely reported by regulatory agencies, as wildfire impacts on fluvial networks remain unconstrained. We identify key actions to address this knowledge gap and better understand the growing threat to fluvial networks, water security, and public health risks.

Automated summary

Wildfires globally are increasing in frequency, severity, and extent, impacting approximately 6% of total stream and river length directly between 1984 and 2014, with a growth rate of 342 km per year. When considering longitudinal propagation of water quality impacts, wildfires are estimated to affect around 11% of total stream and river length. This research highlights the significant impact of wildfire activity on aquatic impairment and suggests the need for improved understanding and management of this growing threat to fluvial networks, water security, and public health risks.