At the Flight 93 National Memorial in Stoystown, Pennsylvania, the plants are taking over. Tall, woody Tartarian honeysuckle shrubs collude with spiny, purple bull thistle flowers to steadily claim the surrounding terrain as their own.
But the area isn’t theirs. The Tartarian honeysuckle and the bull thistle — originally from Europe and Asia — are non-native species of this tranquil part of southwestern Pennsylvania, and they’re slowly overtaking plants indigenous to the sloping landscape.
This plant domination is a concern for the National Park Service, which oversees the 2,200 acres of the memorial site. To prevent these invasive species from monopolizing the land, the National Park Service turned to a group of Penn State Altoona students, who developed an interactive, digital directory to help eradicate invasive species and restore the habitat.
The Flight 93 National Memorial resides in the sleepy countryside field where Flight 93 crashed on the morning of Sept. 11, 2001. Previously an active strip mine, the plane crash not only took the lives of everyone on board but also further disturbed the surrounding landscape, contributing to an environment where invasive, non-native plants thrive.
Carolyn Mahan, professor of biology and environmental studies in the Division of Mathematics and Natural Sciences at Penn State Altoona, is more than familiar with invasive plant species and their negative effects on the surrounding ecosystem.
“The non-native species at the Flight 93 Memorial have adapted to colonizing disturbed soil,” said Mahan. “The mining at the site originally disturbed the landscape, and the trucks traveling in and out had seed sources on them that they inadvertently brought in. The non-native species at the site are the ones that were able to take hold the best, and they’re flourishing.”
Invasive species, historically brought to the U.S. as ornamental plants, spread and cover the area around them, clashing with existing plants and dominating the landscape. Non-native plants thrive in this environment, at the sacrifice of domestic plants, turning the once diverse terrain into one homogeneous crop.
Preventing the slow annexation of Pennsylvania’s native plants at the Flight 93 Memorial is a priority for the National Park Service. In 2013, Mahan assembled a team of environmental studies students and faculty and participated in the first year of restoration efforts. They’ve been involved ever since.
“The National Park Service needed a way to track the locations of all the non-native plants and document how to control them,” said Mahan. “We sent a Penn State DuBois student to identify the non-native plants and then map them into a GPS system. Then a Penn State Altoona student took that data and developed an interactive map that identifies the plants and provides links to information on how best to treat them.”
Garrett Harris, a former Penn State Altoona student who developed this interactive map, essentially created the files for the project from scratch.
“The data we collected included lists of all the non-native species found at the site and the latitude and longitude for each plant’s specific location,” said Harris. “I converted each latitude and longitude file into a KMZ (Keyhole Markup language Zipped) file by using a function within the Google Earth program. This function combined the new location files with the list of species locations to create a file we imported into Google Earth, which then created the new interactive map.”
But this first iteration would not be the last. Mahan wanted the map to provide the National Park Service with even more information about the invasive species at their fingertips.
“Dr. Mahan wanted a link for each plant so that anyone looking at the map could pull up data for identification and control purposes,” said Harris. “To add this characteristic data I had to convert the KMZ files over into ArcMap (which is used primarily to view, edit, create and analyze geospatial data) so I could add all the attributes for the user to access.”
And sometimes the most important attribute is the most obvious.
“The first thing we want to make sure of is that the plant is identified correctly so no one attempts to remove native species,” said Mahan. “Then we give them information on how to eradicate the nonnative species as effectively as possible.”
There are a multitude of factors at play when trying to remove invasive plants. Physically extracting them from the ground can be difficult enough, but keeping them from re-sprouting is a science in itself — as any gardener who’s planted mint directly into the ground can attest.
“There are certain times of the year that herbicides are more effective,” said Mahan. “When a plant is actively growing, when it’s pulling nutrients out of the soil, that’s the best time to apply an herbicide because the plant will pull the herbicide up faster. Some invasive species even require repeated herbicide treatments before they’re completely eliminated.”
Eliminating invasive plants for good also requires nonchemical tactics. Ecologists — professionals who study the relationships between plants, animals and their environments — often recommend planting certain native species while working to exterminate the non-native ones.
“If you can replace the non-native plants with a dominant, native plant cover you can create a stable habitat that’s resistant to invasive, non-native species,” said Mahan.
And a stable habitat is important, especially when it’s the background of a national memorial that draws an average of 300,000 visitors every year.
“We can’t always be there in person,” said Mahan. “But I think we’ve given the National Park Service a valuable tool to help restore the landscape.”
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