Last week, we mentioned a USGS study that described how wildfires might impact organisms on our terrestrial landscape. But wildfires can also devastate our freshwater ecosystems as well.

USGS Western Ecological Research Center biologist Adam Backlin explains how in this article reprinted from the newest issue of WatershedWise, the quarterly publication of the Los Angeles and San Gabriel Rivers Watershed Council (LASGRWC):


Wildfires clearly cause great damage to our terrestrial landscape -- neighborhoods lost, hillsides and forests reduced to blackened barrens, and our air thickened. But often unseen to the public is the impact of wildfires on the creeks and streams of Southern California.

At the U.S. Geological Survey (USGS), my colleagues and I are studying conservation biology at a landscape level. We look at how each organism is connected to the greater landscape, which in turn, helps us understand how each organism is impacted when a major event hits that landscape.

So when the 2009 Station Fire exploded across the landscape, we were concerned about impacts on aquatic species. Southern California streams are actually home to a number of rare amphibians and fish, such as the Sierra Madre yellow-legged frog (Rana muscosa), the California red-legged frog (Rana draytonii), the Santa Ana sucker (Catostomus santaanae), and the unarmored three-spined stickleback (Gasterosteus aculeatus williamsoni), among others. It is important to conserve these federal- or state-protected species in order to maintain the biodiversity of this region.

After a wildfire occurs, a number of impacts can hit the aquatic ecosystem. Loss of tree canopy means less shade for the creeks and more fluctuations in water temperature. Destabilized soil results in higher sedimen loads and altered water chemistry. Even worse are ash deposits and dried, loosened gravel that only need mild disturbances to form landslides and completely bury a stream section. Any amphibian or fish that relies on oxygenated, flowing water will be impacted.

What USGS wants to know is how sensitive are these animals to wildfire processes. Wildfires are a natural phenomenon in Southern California. Historically, the landscape supported widespread populations of these amphibians and fish that experienced local losses from wildfires and post-wildfire processes. Amphibians and fish survived over time by recolonizing from neighboring populations. But as these populations of amphibians and fish become more rare and isolated, they lose the ability to reestablish lost habitat. As the Southern California landscape becomes increasingly urbanized and fragmented, non-native plants and animals invade, and with wildfire frequencies increasing, we have to examine what the survival threshold is for these aquatic animals.

Our research is ongoing. We are mapping areas such as the 2009 Station Fire to estimate future impacts from flooding, landslides and debris flows. We also look at ecological conditions like stream morphology, water chemistry, habitat, disease prevalence and species diversity before and after fire events in different areas. With these data, we can predict how future events will impact the remaining strongholds of our rare frog and fish species.

Hikers and nature enthusiasts are often thrilled to learn that Southern California is home to these hidden aquatic critters. Findings from this landscape-scale research should hlep resource managers develop conservation and fire management plans -- ones that minimize damage risks both to our housing and to our underwater neighbors.

-- Adam Backlin

Top: Among the rare and endangered aquatic species that are severly impacted by clogged and buried streams are the southern steelhead trout, also known as rainbow trout (Oncorhynchus mykiss). Image credit: Tim Hovey/USGS.

Read More:

• Download a PDF version of this story from LASGWC
• Listen to a 2008 NPR story about Backlin's research
• Watch a 2008 YouTube video about Backlin's research
• Look up frog and turtle species in the WERC Reptiles and Amphibians Field Guide