Plummers Island: The most-studied island in North America.

AA secluded parcel of land is surrounded by crystal clear waters, lush greenery and diverse wildlife. A small island in the Potomac River provides the perfect outdoor laboratory for conducting biological research — then, surrounding the island, miles of untouched land whose forests and dense vegetation are a petri dish for the local biota.

Plummers Island, an obscure strip of land called “the most thoroughly studied island in North America,” sits along the side of the Potomac Gorge just off the C&O Canal between Great Falls and Georgetown. The island houses hundreds of rare species, including bats, beetles, moths and invasive plants, and has been home to 120 years of research.

A nonprofit research group, The Washington Biologistʼs Field Club (WBFC) initially leased the land in 1901 and purchased the site in 1906, which included the 12-acre land and a 35-acre parcel on the adjacent Maryland mainland. The site was managed by the WBFC until 1958 when ownership was transferred to the National Park Service. The Club continues to conduct research on the island and provides grants to scientists to conduct research on the island and in the context of the Mid-Atlantic bio-region. Since 1901, hundreds of scientists have studied the islandʼs thousands of plant and wildlife spe- cies through WBFC grants, tracking archival data augmented by their own, to inventory the island’s biota and analyze changes in the indigenous flora and fauna.

“People can go back and look at these specimens and collections and go, ‘Cool, hereʼs what was there 500 years ago,’” said John Brown, an entomologist and former researcher at the Smithsonian. “It just sets the stage and creates the foundation of knowledge that you can look at over time.”

The WBFC supplies grants of up to $5,000 to scientists for transportation to the island and equipment for when they’re there. Currently the club totals 60 members with four applications pending. First an all-male club, the WBFC became more progressive when it opened to women members in 1996. In 2005, the group welcomed Maria Alma Solis as their first female president.

As a nonprofit organization, the WBFC like others must disperse five percent of its endowment yearly towards its objective of promoting biodiversity and ecological research on the island. The club maintains its right to research the island, but has occasionally challenged the Park Service over whether they are permitted to take organisms from the island for further research.

Taking inventory of all Plummers Is- land’s wildlife is one of the clubʼs aims, but since the proposal to expand the American Legion Bridge through the island has threatened the natural habitat, members have shifted their focus to protection. Rushed, botanists, entomologists and other scientists need to complete as much research as possible before state officials put the plan in place, they say. However, club members are hopeful that the recent change in Maryland’s leadership from Gov. Larry Hogan to Gov. Wes Moore may bring about the delay or even the elimination of the plan to expand the bridge onto the island.

“There is a chance that our efforts in promoting scientific knowledge are being understood, heard and appreciated,” said Dr. Shannon Browne, a Whitman alum and Senior Lecturer at the University of Maryland in the College of Agriculture & Natural Resources. “Weʼre very thankful that we might be saving the island after all.”

The bridge expansion was originally proposed to ease traffic, but the environmental consequences are extensive. If implemented, construction would jeopardize the biodiversity historical research and trends on the island.

Unfortunately, the club has another enemy encroaching, as well — a biological one.

On her knees, Jil Swearingen sifts through plants, searching for the invasive “grand ivy” rooted in the soil. Next, she tirelessly yanks out each stem of “garlic mustard.” Finally, she stands up: she’s finished removing all the invasive species in “plot 19,” one of roughly two dozen, 10-meter tracts scattered throughout the island cordoned to document the impact invasive species have on the native organisms.

In 2012, The WBFC formed an Invasive Biota Committee to research the destructive ramifications of invasive species on native ones. As part of the process of observing the biome, the plots go largely undisturbed land for five to ten years. Some researchers visit multiple times each month, while others only visit a few times a year to document the ongoing differences each species present.

Their findings were concerning: there were already more invasives than natives. But their data also yielded proof that the native species rebounded when invasives were removed. The committee was granted permission by the overseeing club members to start extracting invasive species with their hands and safe, targeted chemicals.

“It was clear that if we didnʼt do anything at all, there would be more and more of the invasives and less and less of the native species,” said Swearingen, biologist and Chair of the Invasive Biota Committee. “Weʼre really worried about invasive species spreading and becoming even more problematic. You canʼt just watch them, you actually have to get out and do something, and we all feel dedicated to doing something about it.”

The recent proposal to expand the Legion Bridge will worsen the problem of invasive species on the island, Swearingen said. The club is still actively lobbying for a more environmentally friendly proposal.

Diving down just below the tree tops, a bat perches itself gingerly on a branch. Hoping to find the nearest pool of water, the bat sets off and uses echolocation — a batʼs ability to locate objects through sound frequencies — to locate water close by. Beside it along the tree line are hidden microphones capturing its every sound.

Dr. Browne sifts through hours of these recordings, filtering out non-bat wave frequencies. She listens intently in order to identify each bat call in hopes of discovering a new species on Plummers Island.

Beginning her research in 2022, Browne pooled together a group of her college students to study bats. Mainly researching on the island, Browne set off on a goal: to find all ten bat species known to live in Maryland.

The American Legion Bridge looming, she decided to expand her research to not only catalog the number of bat species on the island, but prove that if Hoganʼs plan to dig up part of the island were to go through, the state would be removing an essential habitat for specifically endangered bat species. There is a sense of urgency to conduct as much research as possible to continue the 120 years of data on the island as long as possible, Browne said.

After sifting through recordings, she ultimately memorized all the calls, she said. Browne analyzed the time between each to determine what behavior the bat was engaging in and from which bat species each call originated. She primarily used their commuting calls, but other measurements help her compare statistics against one another to narrow the scope on which species are present on

Plummers Island, she said.

“Itʼs not just science, but also an art,” Browne said. “I try to think like that species: which kind of trees, water and insects do they prefer?”

Depending on the species, the locations of the recording devices must change. Bridges, cliffs, rock crevices, forests, water pools, high trees, an abandoned cabin — there’s been strategy in placing the devices to record all ten species.

Browne and her team experienced some unique challenges: bats are nocturnal, so they had to collect their data at night. Before sunset, the team would replace the SD cards and power on the devices to record all night. The organization involved in managing all of the locations came down to teamwork, she said.

On Nov. 11, her researchers ended their surveys and picked up all their equipment — but Browne herself is still working. Her results documented on the island six out of the ten bat species in Maryland. She is currently in the process of applying for another grant to purchase additional equipment and survey more frequently in new locations.

Once Browne discovers which species are present on the island, she makes recommendations to help those threatened and endangered species. Saving these species is not just important for their survival, but for human survival as well.

“I want to inspire and educate future generations, influence policymakers in their decisions so that they prioritize environmental health and wildlife health, Browne said, “because itʼs all tied to human health and because itʼs the right thing to do.”

At dusk, John Brown hops out of his truck, lugging moth traps made from buckets, lights and ammonia along with him in hopes of catching as many moths as possible throughout the night. Thirty minutes later, he climbs back into his car and heads back home, excited to go out collecting again in the morning.

Brown, an entomologist specializing in Lepidoptera at the Smithsonian, worked to inventory of the kinds of “Tortricidae” moths present on the island from 1990-1999. He compared data from 1901-1910 to see how the species varied over time.

To collect his data, Brown set up traps all across the island hoping to capture the moths. Blacklight traps, Brownʼs preferred collection method, proved to be the most successful method of catching them in bulk. He stuck buckets on the ground with a light just above, attracting the moths. As the moths fly around the blacklight, they fall into the funnel below the light, and are trapped in the bucket, where they are killed by ammonia fumes.

With grants from the WBFC, Brown hired students to help him set up traps and collect specimens. Every Saturday morning, Brown then collected his buckets of dead moths, beetles and other insects, laid them out on his kitchen table and started to sort — a process that lasted four to six hours. With insects, scientists must pin them on a board and label the species so other scientists in the future can look at the mothsʼ dimensions and species.

“It is just a really enjoyable time chatting about entomology, pinning and labeling insects every week for ten years,” Brown said. “Iʼve always loved research, and I would publish six or seven or eight papers a year.”

It was when Brown realized the tortricid was declining that he decided to focus more on the how and why uncovering how the species and numbers have changed over time. The most baffling part of his entire experiment was realizing that scientists in the early 1900s collected more moth species than he did by just using a lantern and bedsheets, Brown said.

Brown decided after ten years that he would publish his findings and end his research to eliminate bias because previous studies were also conducted over a ten-year period.

“Whenever you finish a research project, you realize that you have raised more questions than you have answered, and thatʼs whatʼs cool,” Brown said. “Thatʼs what leads to more research.”

Though Brown retired in 2014, at age 71 today, he continues to commute to the Smithsonian daily, paying for public transportation to identify insects, he said.

“This is really typical of older scientists at the Smithsonian and I think elsewhere across the globe,” Brown said. “You just develop this passion for something, and just because youʼre done or youʼre tired, you still have it.”

While hiking across a back trial, Warren SteiWhile hiking across a back trial, Warren Steiner spots dying ash trees and rummages around trying to find the cause of death. He comes across a few small green beetles, each the size of a grain of rice, hovering around the trunk. Steiner picks one up and later finds it to be an emerald ash borer, a rare pest origi- nating in Asia — previously undiscovered on Plummers Island.

Part of a lineage of research that began in 1900 and ended in 2000, Warren Steiner, an entomologist specializing in Coleoptera at the Smithsonian, studied the beetle population changes on Plummers Island. He and other entomologists found that some species disappeared as the years went on, but a few new species were also discovered.

In the 80s and 90s, Steiner and his colleagues made several trips to the island, including many nighttime vigils. Their UV light attracted a multitude of beetles, but Steinerʼs favorite capturing method is a fluorescent tube that projects onto a white screen, he said.

Steiner used Malaise traps — tent-like structures that lure the insects to the highest point of the tent, where they fall into a container below — primarily used to catch flying beetles. He also knew how to get down in the dirt, sifting through the grass and turning over logs, hoping to scoop up with his hands and then document as many species as possible.

In the early years of the WBFC, researchers discovered 53 new beetle species active on the island. Steinerʼs study from 1976-2006 showed that 29 out of the 53 species were still present alongside a new eight.

“Iʼve had fun naming them, describing what they do and documenting the other critters that share the planet with us,” Steiner said, “hopefully — can do something about their decline.”

Invasive populations threaten insects’ survival significantly. The shift in food type and availability, researchers say, will likely cause the beetle populations to diminish over time or even disappear.

There are few places on the earth as heavily studied as Plummers Island. The area is uniquely diverse as a biodome because humans in modern times have never tried to occupy it or build through it. It’s had millennia to just be.

After purchasing it, the Park Service made it outright illegal to disturb the area. The plans to construct a bridge seek to end that protection.

The island’s value to the scientific community nationally and nearby is irreplaceable, Steiner said.

“Plummers Island is just as interesting on a local scale because of its history,” Steiner said. “The islandʼs diversity and its being near scientists makes it that much more special.”