This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What is helping some Florida wildfires burn hotter and spread farther? A University of Florida study suggests cogongrass, an invasive grass that has spread across much of Florida and the southeastern United States, is adding more fuel to the landscape.
The invasive grass can create conditions that allow fires to spread faster and burn with longer flames that reach the tree canopy, particularly during Florida's spring season. The study, published in Fire Ecology, examined how cogongrass affects characteristics that influence fire behavior across different environmental and seasonal conditions. Cogongrass forms dense patches that can displace native vegetation, reduce biodiversity and alter ecosystems.
Since its introduction in the 1930s, cogongrass has spread to almost every county in Florida, though it is most extensive in northern and central Florida. "When you have cogongrass, you have greater fuel loads, so that means there's more dead vegetation on the landscape that can fuel fires," said Alan Ivory, a graduate student at UF's West Florida Research and Education Center who led the study. "We found faster rates of fire spread and longer flame lengths, and we also found an increased likelihood of fire transitioning into the tree canopy." That transition, known as a crown fire, can present additional challenges for firefighters because fire moves from vegetation on the ground into the tree canopy.
"When you go from a ground fire to a crown fire, it becomes more difficult to suppress and requires more resources," said Ivory. The researchers also found that the effects of cogongrass on fire behavior varied by season. The greatest differences occurred during late winter and early spring, a period when prescribed fire is widely used across the Southeast.
That finding is particularly important in Florida, where prescribed fire is an important land management tool. "The Southeast is a hot spot for prescribed fires, and Florida in particular is a model for prescribed fires across the country," said Victoria Donovan, assistant professor of forest management at the UF/IFAS School of Forest, Fisheries, and Geomatics Sciences. "We use prescribed fire to enhance our ecosystems and the services that they provide to people, but we also use prescribed fire to reduce wildfire risk." The study also produced a surprising result.
Ivory initially expected cogongrass to have its greatest effect on fire behavior during summer, when the grass is at its tallest and most vigorous. Instead, the researchers found that the plant's moisture during this period helped suppress fire spread. Donovan said the research also suggests that changing environmental conditions could influence how cogongrass affects fire behavior in the future.
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