Title image: Burned neighborhoods in Louisville, Colorado after the Marshall Fire. (Photo by Glenn Asakawa/University of Colorado Boulder)
Wildfires ravaging Western Canada last week have reduced the town of Jasper, Alberta, near Jasper National Park to ashes, with local governments estimating that nearly half of the town’s buildings have been damaged or destroyed.
The fires offer a lesson for the Colorado Rockies and the people who live there: When wildfires spread through urban areas and burn down man-made structures, the impacts can be far-reaching, says Lauren Magliozzi, a biogeochemist in the Department of Civil, Environmental, and Architectural Engineering at the University of Colorado Boulder.
Lauren Magliozzi takes water samples in Superior, Colorado, after the Marshall Wildfire. (Photo by Adam King)
Magliozzi studied how the Camp Fire in California in 2018 and the Marshall Fire in Colorado in 2021 affected local water quality and ecosystem health. His team found that toxic metals such as copper, lead and zinc found in ashes from buildings and cars can leach into streams and rivers, threatening the safety of water and the health of aquatic life.
“You need healthy ecosystems to have healthy drinking water sources,” said Magliozzi, who is also a researcher at the University of Colorado Boulder’s Arctic and Alpine Institute.
As climate change increases the frequency and intensity of wildfires, Magliozzi shares his thoughts on the difference between urban and wildland fires, and what people can do to protect their homes and local ecosystems.
Are all wildfires bad for the environment?
Wildfires, which primarily burn vegetation, benefit ecosystems by releasing nutrients into the environment and making them more resilient to fire.
But wildfires are no longer beneficial when they enter the man-made environment and become what scientists call urban conflagrations, whose fuel is not primarily plants, but homes, vehicles, trash, batteries, and everything stored in garages. Burning these materials releases a wide range of chemicals into the environment, and efficient stormwater systems in cities can flush these complex pollutants directly into surface waters.
What contaminants can leach into the environment?
Surface water samples taken after the 2021 Marshall Wildfire found elevated concentrations of toxic metals, including zinc and manganese, in Coal Creek, which runs through Superior and Louisville, where the fire began, and were able to trace the sources of these metals back to the built environment and stormwater.
How do heavy metals affect ecosystems?
Two years after the fire, levels of some toxic metals in Coal Creek still exceeded US Environmental Protection Agency standards for aquatic life — thresholds above which aquatic life is harmed.
They also looked at the specific organisms that inhabit the stream. Although algae growth remained constant in the burned urban areas, many of the organisms that eat the algae were significantly reduced. For example, they found that algae-eating mayflies, once common in the stream, were reduced in number after the fire. The decline in mayfly populations suggests that the algae may be absorbing metals, which are then transported up the food chain.
A mayfly magnified 10 times. (Photo by Camryn Miller/CU Boulder)
While sensitive species have declined, organisms that can tolerate poor water quality, such as leeches, have increased in Coal Creek.
Should people who live near Coal Creek be concerned about the quality of their drinking water?
Fortunately, Coal Creek is not used as a local drinking water source, but a major urban fire like this occurring next to a drinking water source would be very concerning.
But the impacts of urban fires go beyond mayflies in streams: Some of the pollutants found in streams after urban fires have yet to be quantified, and we are only beginning to understand what organic compounds are released into water systems after fires.
Why have there been more cases of wildfires spreading to urban areas in recent years?
Over the past two decades, there has been a significant increase in housing built in fire-prone areas. As communities relocate to these areas, so do the human-caused activities that can cause fires, such as discarded cigarettes and power lines. Extreme weather events, such as high winds like the Marshall Fires and last year’s Hawaii fires, also increase the risk of urban fires.
A burned car in Superior, Colorado after the Marshall Fire. (Photo by Lauren Magliozzi/University of Colorado Boulder)
Is there anything we can do to protect our ecosystems and our homes?
One of the lessons learned from our research is that in the immediate aftermath of a major urban fire, stormwater can be prevented from reaching streams and surface waters.
In the long term, it’s important to prevent big fires in our cities. We need to improve our community planning and look at ways to build homes that are less flammable. In April, we proactively shut down power lines on windy days, which is one way we can reduce fire risk.
People who live in fire-prone areas can reduce their risk by practicing fire-sensitive landscaping and creating fire-safe spaces around their homes. Fire-sensitive landscaping includes pruning trees, cutting back vegetation, and creating borders, such as gravel buffer strips, around their homes.
CU Boulder Today regularly publishes Q&As in which faculty members share their views on news topics from the perspective of their academic expertise and/or research/creative work. Responses reflect their experts’ knowledge and interpretations and do not necessarily reflect the University’s position on the issues. All published content may be edited for clarity, brevity, and adherence to University style guidelines.
