Too Much of a Good Thing?
BY ANNMARIE CORNEJO
Examining the cumulative environmental impacts of fire retardants
Fourth-year plant sciences major Sawyer Claussen stands
at the site at Cal Poly's Escuela Ranch where he is doing
research on the impact of fire retardants on native grasses.
At Cal Poly’s Escuela Ranch just north of the main campus on Highway 1, Cal Poly professors and students are engaged in a timely research project to determine the long-term environmental impacts of fire retardants commonly used to combat wildfires that are increasingly more frequent especially at the wildland-urban interface.
Fire agencies have long used aerial retardants to slow the spread of wildfires near communities and other valuable resources. The thick, reddish hued substance dropped from airplanes is a combination of chemicals and water, most commonly Phos-Chek, which is a fertilizer-based mixture. The ammonium phosphate slows the spread of fires, and subsequently helps plants grow the following rainy season — but some researchers worry they are the wrong ones.
“In the last decade, California wildfires have become more and more common and of such high intensity that they are destroying communities and precious wildland areas,” said fourth-year plant sciences major Sawyer Claussen. “It is a difficult topic with economic, safety and environmental factors that must all be considered. What we are looking at is the lasting impacts of current practices on plant biodiversity and productivity. We could potentially be perpetuating the problem by making the landscape more susceptible to another fire.”
The research being done at Escuela Ranch is just one of many active projects for a team of Cal Poly faculty and students through a four-year, $572,959 grant awarded from the Gordon and Betty Moore Foundation, in addition to a $90,000 award from the California State University Agricultural Research Initiative, to assess the long-term implications of repeated applications of fire retardant to soil, groundwater and vegetation.
The multidisciplinary project, titled “Increasing Fire Resiliency at the Community Scale through Planning and Fire Ignition Prevention,” is being led by Assistant Professor Stewart Wilson in the Natural Resources Management and Environmental Sciences Department, along with faculty and students from the Plant Sciences, BioResource and Agricultural Engineering and Mechanical Engineering Departments.
Plant Sciences Department Head Scott Steinmaus is working with students such as Claussen to investigate the impact of fire retardants on plant biodiversity. Ultimately, the fertilizer used in retardants exacerbates the growth of non-native species of grasses. Those grasses, like ryegrass, wild barley and oats, tend to grow fast and tall, produce seed that is dropped to the ground quickly, and die off earlier than native species — potentially making those areas more prone to additional fire risks. “The iconic golden hills of California that we are so familiar with, those are all non-native, invasive grasses that have become commonplace here,” Steinmaus said. “These invasive grasses end vegetative growth and die in late March or early April, becoming flammable from April to November until it rains again. California native perennial grasses such as purple needlegrass would normally still be partially green and less likely to burn even through the summer.”
Steinmaus’s team of students are testing a possible alternative at their field site at Escuela Ranch: a fire retardant that is salt-based using magnesium chloride, eliminating the fertilizing component and potentially allowing native grasses to once again flourish. Both retardants are being compared side by side by being applied in late summer with professional fire retardant application crews and equipment, simulating a commercial application.
“We have many assessment metrics that we are using to measure the retardants’ impacts, but photosynthetic performance is one of our main ones,” said Claussen, who spent the summer participating in the college’s Summer Undergraduate Research Program, looking specifically at the impact of the different fire retardants on the germination, growth and physiological performance of two grass species. “Once the fire is put out and the retardants intensify the growing patterns afterwards, we are looking to understand what level it is hindering or helping biodiversity of native and non-native plants and potentially affecting later fire cycles.”
The students tend to the more than 50 test plots at Escuela Ranch where both native and non-native grasses grow, collecting data at the site and samples to further analyze in the laboratory. The trial is in the second of a four-year plan. Additional research for this project is also being done across the college and university on the impacts to soil, water and ember testing.
“This experience definitely ties into my overall goal of working in agriculture and the natural resource industry to implement more environmentally sound practices to preserve our wildlands and climate,” Claussen said. “Knowing how these retardants, which are our main tools for fighting wildfires, affect landscapes post application is very important to having informed management practices and stewarding our wildland ecosystems the best we can.”
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