March 26, 2024 | Josiah Dallmann | Sustainability
February 13, 2025
Every year, tens of thousands of soldiers join combat training exercises at Pennsylvania’s Fort Indiantown Gap National Guard Training Center. The 17,000-acre base is also the last natural home of the eastern regal fritillary butterfly. The favorite fields of this rare and striking butterfly are used to train troops on hand grenades, live fire artillery, and tank maneuvers.
Despite the butterfly’s precarious position, conservationists don’t want bombing exercises stopped or moved. In fact, without this human-made disturbance to their environment, this species could disappear. Land managers at Fort Indiantown Gap work closely with biologists at the US Fish and Wildlife Service and state agencies to manage the butterfly’s habitat. They use geographic information system (GIS) technology to record the butterfly population, plan ways to improve the habitat, and analyze how the butterfly responds to changes.
Since 1992, the National Guard has actively managed the butterfly’s habitat. They have set prescribed burns, mowed, seeded, and transplanted the violets the butterfly needs. Biologists have found that violet density increases four times when tanks trample the land and eight times after a prescribed burn.
“A lot of environments on the East Coast want to be a deciduous forest, so any time there are open fields that don’t have some sort of disturbance to keep it open, it pretty much just turns into a forest,” said Mark Swartz, a wildlife biologist with the Conservation Division at Pennsylvania’s Department of Military and Veterans Affairs. “At the Gap, we see a lot of disturbance, from the military training and also our own land management.”
While the western subspecies can still be found in native grassland, the eastern regal fritillary butterfly, a large, bright orange and black species with distinctive white markings, has been in continual decline as its natural habitat gradually disappears due to urban development and agricultural expansion.
The eastern regal fritillary depends on three elements for survival: host plants for the caterpillars, nectar sources for the adult butterflies, and grass to use for shelter. The disturbances created by training activities and land management at Fort Indiantown Gap provide all three.
The only plant that the butterfly’s larvae will eat, and therefore the only available host plant, is the violet. “Violets are a very disturbance-dependent species,” Swartz said. “They drop out when other plants start growing up nearby.” The butterfly’s preferred nectar sources and habitat of open grass both require regular disturbances. “Warm-season grass is disturbance-dependent too,” he explains. “Grass is used by the butterflies for cover in all life stages.”
In areas of the base that experience less disturbance, the environmental conditions required by the regal fritillary are maintained in other ways. “Fire is an important ecological management tool,” said Virginia Tilden, a conservation biologist with the Conservation Division at Pennsylvania’s Department of Military and Veterans Affairs. “We use prescribed fires to clear out taller grass growth and prevent forest fires in the area, but it also helps maintain the open spaces of native vegetation, and that’s why the butterfly is here.”
“When I first started working on this project in 2002, we were still using paper maps,” Swartz said. “We would look at the maps, pick out an area, and then go look and see what was there.” By 2010, Fort Indiantown Gap staff had started to use GIS to map the butterfly’s habitat. They created map layers with data about the environment to track and analyze the area’s fragile conditions.
The isolation of the subspecies leaves it vulnerable. In recent years, the Gap has partnered with the Pennsylvania Game Commission, the US Fish and Wildlife Service, ZooAmerica, Temple University, Pennsylvania Western University, and Penn State DuBois to establish new sites in the state where the species can thrive.
To track the current butterfly population and environmental conditions, and aid in developing new places where the species can thrive, Fort Indiantown Gap staff developed a GIS-powered workflow. “We started using ArcGIS Survey123 to create public apps for the students who will be helping us at the reintroduction sites,” Tilden said.
Volunteers and staff use the app to count adult butterflies and the locations of violets and other nectar plants. They share the maps and data on a central website so everyone can see it in real time.
Despite these conservation efforts, the future of the eastern regal fritillary butterfly remains uncertain. The species’ numbers remain low, and in August, the US Fish and Wildlife Service proposed adding it to the endangered species list. Work is now underway to adapt GIS tools and apps to release and track the adult butterflies that ZooAmerica propagates in carefully chosen sites across Pennsylvania.
Conservationists and land managers collaborate with GIS tools. “If we need data, we can email Penn West and the students will go out, use the nectar plant density app, collect all the information, and upload it,” Swartz said. “It’s nice to have partners collecting data we can access almost in real time, because some of our sites are 300 miles away. Instead of waiting while we drive four hours each way, we have the data as soon as they finish the survey.”
The sharing goes both ways. “If somebody needs a GIS file that we have, like site information or game lands, we share back and forth. It’s a great resource.”
Conservation teams can quickly adjust their actions based on the latest data, enhancing efforts to protect the eastern regal fritillary butterfly. They work with a deeper and more immediate understanding of ecological dynamics and conservation needs. This level of informed collaboration, together with technology, helps make sure that every action taken is as effective as possible in keeping the butterfly’s habitat safe.
Learn how conservation organizations protect biodiversity with GIS.
