A recent study from the University of Florida researched the effects of prescribed fires on certain butterflies.
Matt Thom, a former UF doctoral student, conducted the study as part of his dissertation. He now works in soil management research at the U.S. Department of Agriculture.
The study focused on the larval stages of caterpillars and revealed that while the elfin frosted butterfly needs prescribed fires to live, that type of forest management also causes problems for their survival.
Caterpillars thrive off a host plant. The elfin frosted butterfly uses the sundial lupine and pupates (transforms from a larvae into a pupa or cocoon in order to undergo metamorphosis) in the leaf litter or in the base of the soil, according to Thom. Because the frosted elfin only has one generation per year, there are concerns the fires could wipe them out.
He said the frosted elfin’s reproduction season is around the same time when conditions are right to have prescribed burnings.
Thom said the pupae stage is where the frosted elfin spends a majority of its life, ranging between seven to nine months, and leaving the butterflies prone to fire damage, due to their immobile state during the transformation.
He said that frosted elfin butterflies could not actually be used for the study because they are so rare. It was too difficult to gather and rear them in captivity, so the study used the atala hairstreak butterfly instead, which is closely related to the frosted elfin and grows in similar conditions in South Florida, according to Thom.
State forest ecologist Brian Camposano said prescribed burning is crucial to the well being of the forest’s ecosystem.
The host plant of the frosted elfin is a fire adapted plant and it needs fire to survive, he said.
Fires have always been a naturally occurring process in southeastern forests, usually as a result lightning.
Thom said that even though they could negatively impact the butterfly population, the host plants need the fires to survive. Those fires help the plants regenerate, and post-fire they sprout vigorously.
Thom said fires release nutrients back into the soil by combusting the standing vegetation and converting it into simpler molecules that regenerate and provide a flush of nutrients to any vegetation or seeds that survived.
Camposano said he’s aware of the issue involving the frosted elfin. The study recommended burning in such a way that some host plants would be left alive, so the insect still had a way to develop.
“That’s not something that we can always control, and it’s not always something we can do,” Camposano said. “But the idea is kind of to provide a mosaic of burned and unburned patches throughout a particular habitat or ecosystem.”
He said that Ralph E. Simmons State Forest is one of the few places in Florida the frosted elfin can be found.
The Florida Forest Service has been burning and managing the park in the same way since they’ve acquired the property, according to Camposano.
“It’s hard for us as an agency, and other agencies as well, to burn for species specific objectives,” he said. “Our agency definitely burns on what’s good for the ecosystem as a whole.”
Camposano said the park and other areas where the frosted elfin can be found are aware of the issue are trying to cause the least amount of impact when conducting prescribed fires.
“A lot of the times our goals are actually to remove fire lines,” he said. “We want less disturbance on the ground.”
One strategy is to burn every other unit every other year to leave some host plants standing or to burn during a season that does not disturb the frosted elfin’s life cycle, according to Camposano.
“It is particularly interesting that a butterfly can be so vulnerable to fire, but at the same time require fire for its life cycle and its continuous existence,” Thom said.
He said the host plants are easily out competed by many other kinds of vegetation and without fires occurring frequently enough, the host plants would eventually disappear. The butterflies would not be able to survive then either.
“On the other hand, too much fire, no butterflies,” Thom said. “So striking a balance between management, different management activities and requirement mandates is very important for these organisms.”