Skip to main content
Community scienceConservation

Beware of Invasive Species

By February 23, 2022March 24th, 2022No Comments
Photo of a carpet of plants growing beside a trail and growing up trees. nvasive species are crowding out native species and smothering trees beside the trail. © Frank Gallagher
Invasive species are crowding out native species and smothering trees beside the trail. © Frank Gallagher

By Frank Gallagher, NANPA Blog Coordinator

National Invasive Species Awareness Week runs from February 28 through March 4, 2022. The goal of the week is to “raise awareness about invasive species, the threat they pose, and what can be done to prevent their spread.” There are many reasons nature photographers should be concerned about invasive species and many ways photographers can help. For example, I’m in Rock Creek Park with my camera almost every week, and I see the effects of invasive species every time I go hiking and photographing.

Photo of a dozen or so people puling weeds in a forest.  Volunteers removing invasive winged euonymus (Euonymus alatus) during a Rock Creek Conservancy work trip. © Frank Gallagher
Volunteers removing invasive winged euonymus (Euonymus alatus) during a Rock Creek Conservancy work trip. © Frank Gallagher

What are invasive species

By definition, an invasive species is something that doesn’t belong here because of its potential to harm the ecosystem, economy, and/or human health. Examples include zebra mussels, Asian carp, emerald ash borers, and English ivy, none of which are native to North America.

Invasive species can cause massive damage. Zebra mussels, for example, are native to Eastern Europe and Western Asia. They probably came to the Great Lakes in ballast water from cargo ships in the 1980s and have spread across large areas of the U.S. They clog water intake pipes, outcompete native species and filter out algae that other species rely on for food. Asian carp threaten the fishing and recreation industries in and around the Great Lakes. Solutions aren’t cheap. An $858 million U.S. Army Corps of Engineers project is planned to install defenses in Illinois aimed at preventing carp from reaching Lake Michigan.

The emerald ash borer came in from Asia in the early 2000s, has spread into at least 36 states, and has destroyed tens of millions of ash trees. English ivy, while often planted as decorative ground cover, will choke out anything else growing on the ground. Ivy will also grow up and eventually kill trees, creating an “ivy desert” where little else can grow. Particularly vulnerable are the dead trees with cavities used as nests by owls and other species, depriving them of nesting sites and potentially moving them to less optimal places.

When invasives take over an area, local birds and other species are then deprived of the native leaves, flowers, and berries they rely on for food and shelter. Native plants and wildflowers lose space to grow. And photographers don’t get the opportunity to capture images of native flora and fauna.

Yet, when invasives are removed, nature can rebound. I’ve seen this play out over several years working and volunteering with Rock Creek Conservancy here in Washington, DC. The Rock Creek Conservancy is dedicated to protecting Rock Creek Park and is the “philanthropic and stewardship partner” of the park. Its mission is to restore Rock Creek and its parklands as a natural oasis for people to enjoy, appreciate, and protect.

Go to any park or natural area near where you live and you’ll see similar problems, along with great organizations and volunteers trying to make a difference.

Photo of a leaf-covered forest floor cleared of plants. An area that has been cleared of invasive ground cover, ready for native plants to regenerate. © Frank Gallagher
An area that has been cleared of invasive ground cover, ready for native plants to regenerate. © Frank Gallagher

The future of the forests

Among the Conservancy’s restoration projects are five mini-oases, areas set up as “proof of concept” sites. The goal, says Community Engagement Coordinator Lindsey Cathcart, is “to use people-powered restoration to reduce invasive plant ground cover to less than five percent, restore the native plants of those sites, and foster a stewardship ethic in the surrounding communities so neighbors will take action at home, and engage the communities surrounding these oasis sites in performing the majority of the work required to achieve these goals. Removing an infestation of invasives can take a long time – these plants grow quickly, and that’s why they’re invasive in the first place. So we need to continue to revisit the same areas many times over a long period of time in order to reduce the invasive community to a point where minimal upkeep will be needed.

“The oases allow us the opportunity to fully restore these small portions of the park (two to five acres), which is a very visual process. Park visitors can walk through an area and see one side of the trail is gnarled and densely populated with invasives and the other is cleared out of invasives, with native varieties planted to help supplement the natural regeneration of the native plant community. Focusing on these small areas helps us create these informal educational opportunities for people to see the challenges the forest faces, and the resources (time, money, volunteer power) it takes to restore the forest. In the long term, we hope the oases serve as a model, and inspiration, for a broader scale restoration of the entire park and forest.”

During 2021, in the midst of a pandemic, volunteers still managed to clear more than 400 trees from English ivy, plant 465 native plants, remove more than 36,000 pounds of trash, and clear large areas of invasives through 250 volunteer events involving almost 8,000 volunteer hours. All volunteer events are conducted in partnership between the Rock Creek Conservancy and the National Park Service.

Photo of wildflowers. Native wildflowers, like the Virginia spring beauties (Claytonia virginica), come back when the land is cleared of invasives. © Frank Gallagher
Native wildflowers, like the Virginia spring beauties (Claytonia virginica), come back when the land is cleared of invasives. © Frank Gallagher

The problems with invasives

The mini-oases are located in Rock Creek Park. Created in 1890, the nearly 3,000 acre park is the oldest urban park in the National Park Service. About 250 species of animals (not including insects) live in the park, including about 150 species of birds. It’s also a waystation for migratory birds in spring and fall, attracting many varieties of warblers, in particular. Coyotes and wild turkeys can also be found in the park, if you know where to look. Plus there are the forest, trails, scenic bridges, and the creek itself as photo subjects. Unfortunately, the park is also home to about 200 invasive species.

In the mini-oases, some of the biggest problems come from English ivy (Hedera helix) and porcelain berry (Ampelopsis brevipedunculata). Cathcart says that English ivy “grows as a mat covering a substantial portion of the forest floor across the oases, preventing plants from small wildflowers to shrubs and trees from accessing resources needed to establish themselves. This essentially halts the natural regeneration of the forest.” Porcelain berry, by contrast, “grows vigorously in areas with sun exposure, so it invades the forest from the edges, growing up over and killing everything underneath of it, including trees, and then working its way inward.”

Invasives are causing three big problems, and a host of smaller ones. According to Cathcart, invasives:

  • “Kill trees and potentially damage infrastructure – English ivy, porcelain berry, and other vines like invasive bittersweet (Celastrus orbiculatus), Japanese honeysuckle (Lonicera japonica), and mile-a-minute (Persicaria perfoliata) generally create the biggest problems, as they grow over the park’s trees, which are already burdened by stormwater erosion and rising summer temperatures, and that extra weight leaves them more susceptible to falling during storms.
  • “Modify habitat – Some invasive plants, such as garlic mustard (Alliaria petiolata) and tree of heaven (Ailanthus altissima), are allelopathic, meaning they can exude chemicals through their roots into the soil they grow in. These chemicals favor the germination and growth of the allelopathic species and prevent other plants from being able to grow in that soil, even after the invasives are removed.
  • “Outcompete native plants – In general, invasive species are able to outcompete their native counterparts for resources due to their lack of natural enemies and life history traits, including the ability to grow earlier and later in the season than other species. Over time, this reduces the diversity of plants, which has negative effects cascading across the ecosystem.”
Native mayapples (Podophyllum peltatum) are spreading in cleared areas. © Frank Gallagher
Native mayapples (Podophyllum peltatum) are spreading in cleared areas. © Frank Gallagher

Results and revelations

So, what do we have to show for all these efforts? Is this making a difference? Absolutely!

“Native herbaceous plants are starting to regenerate naturally,” says Cathcart. “These plants are lying dormant in the seed bank of the soil, just waiting for the invasives to be cleared out. We’ve seen native wildflowers – mayapple, jewelweed, and white snakeroot – all bouncing back in areas that have been cleared of invasive ground cover. We’ve then seen wildlife using these resources – box turtles eating mayapple fruit, migrating hummingbirds drinking jewelweed nectar, and bees pollinating white snakeroot.”

I have followed the progress at one of the oases for almost three years, observing, photographing, and documenting the changes. (I’ve also photographed a number of the volunteer activities.) You can definitely see the difference. In areas that have been cleared, native wildflowers are blooming. Native trees and shrubs planted two years ago are thriving and beginning to attract birds and other critters.

“Other changes are slow,” Cathcart notes. “It will take many years to see the forest understory repopulate and mature.” And it will take continued monitoring and clearing to keep the invasives out.

The photographer’s role

Conservation photography isn’t always dramatic landscapes or endangered charismatic megafauna like tigers or elephants. Sometimes it’s photos of a plot of land threatened by or cleared of invasive species. It might be photos of enthusiastic volunteers working hard to rip out invasives or plant native species. Or, it could be entering your observations and photos into crowdsourcing projects like iNaturalist. There are many ways photos can raise awareness of a problem like invasives. And there are just as many ways photographs can engage communities in the solution.

Rock Creek Conservancy uses photos in many ways: feeding social media; showing impact in reports and newsletters; recognizing volunteers, donors, funders, and partners; and illustrating fundraising appeals. A beautiful photo makes people feel more connected to the park and thus is more likely to inspire them to action. The Conservancy, like many conservation organizations, encourages people to share their favorite photos of the park by emailing them or tagging them on social media (e.g. #loverockcreek on Instagram). Check your favorite local park. They might share your photos with their audience and, if you follow them and their hashtags, you might see a spot or two you didn’t know about but now want to photograph.

Photo of a group of people and dozens of full trash bags in front of a wooded area. Volunteers and some of the dozens of bags of English ivy and other invasives they removed during an activity organized by Rock Creek Conservancy. © Frank Gallagher
Volunteers and some of the dozens of bags of English ivy and other invasives they removed during an activity organized by Rock Creek Conservancy. © Frank Gallagher

What else can we do?

One of the goals of conservation photography is to educate the public about threats to the natural world and prevention is easier than cleaning up afterward. So, what are best practices for preventing the spread of invasive organisms? Here are five things you can do.

  • Americans love our yards and gardens but we should watch what we grow. Don’t plant invasive species. Instead, use native species. Talk to the experts at your local nursery or cooperative extension service. Lead by example.
  • In addition to planting natives, identify and remove current invasives from your yards and decks.
  • Invasives can hitchhike a ride. The National Park Service advises visitors to Play, Clean, Go. Enjoy yourself but, before you leave, clean your gear, brush off your tent, clean your boots, and check your vehicle to remove any seeds or organisms you or your stuff might be carrying, so you don’t spread them to new areas. Out with your dog? Check it, too.
  • Learn about, lookout for, and report invasive species. There is a lot of concern about the spread of the spotted lanternfly in the mid-Atlantic states, for example, and state departments of natural resources are asking everyone’s help in reporting sightings. These departments’ websites often have information on invasives of concern. Conservation groups, like the Rock Creek Conservancy here in DC, will also have information.
  • Volunteer at local invasive removal efforts. Whether you’re helping monitor forest health and spot invasives or pulling them out of the ground at a weed-a-thon, you can make a difference. And, if you have a little extra cash, the local (usually nonprofit) organizations that are leading the fight against invasives can always use donations. If you’re near DC, you can check out upcoming volunteer opportunities through the Conservancy on their events calendar. But don’t just go ripping up plants on your own. In Rock Creek, as in many parks, removal of invasives can only be done under supervision from Conservancy or NPS staff or with a special use permit.

Our native plants, fish, insects, and animals face many problems, from climate change to urbanization to pollution. Reducing or eliminating the spread of invasive species is one thing we can do to help preserve the natural environment we all enjoy experiencing and photographing.

 Frank Gallagher headshotFrank Gallagher is a landscape and nature photographer based in the Washington, DC, area who specializes in providing a wide range of photograph services to nonprofit organizations. He manages NANPA’s blog and can be found online at or on Instagram @frankgallagherfoto.