National Parks Traveler

Traveler Special Report: The Invasion Of The National Park System

By Kurt Repanshek

Rising 30 feet and more above the blue waters of Lake Powell, the gray, crusty band of mussel shells reflects an invasion that has swept through the watery ecosystem practically unimpeded. 

Quagga shells, an Asian native brought to North America in the ballast of ships, are cemented to the sandstone walls that cradle the hallmark of Glen Canyon National Recreation Area in southern Utah and northern Arizona. Skeletal evidence of the invasion has been revealed by the lake's dropping pool that literally left the invaders high and dry.

In a small handful of years since the species was discovered clinging to boats and dock timbers at the NRA’s Wahweap Marina, the small, sharp-edged shells have become about as ubiquitous as the “bathtub ring” that discolors the ruddy sandstone and reflects the dropping lake level caused by a long-running drought. 

The mussels affect both the ecosystem of Lake Powell and the recreational pursuits of many who come to fish, powerboat, Jetski, and simply cool off during the hot summer months. But the invasion, and the ecological and economical impacts the mussels cause, is not the only one confronting the National Park Service as it struggles to preserve natural resources – plant, animal, fish, and fowl – across the National Park System.

The author looks up at the band of quagga mussels clinging to the sandstone at Lake Powell/Joe Miczulski

Enabling the rise of invasive species in some of the parks is the changing climate. According to a U.S. Geological Survey study, warming conditions along the country’s southern border is allowing “a number of tropical plant and animal species [to] enlarge their ranges to the north. They include insects, fish, reptiles, amphibians, mammals, grasses, shrubs and trees. Among them are species native to the U.S. such as mangroves, which are tropical salt-tolerant trees, and snook, a warm water coastal sport fish, and invasive species such as Burmese pythons and buffelgrass. 

“The change is likely to result in some temperate zone plant and animal communities found today across the southern U.S. being replaced by tropical communities,” the study added. “These changes will have complex economic, ecological and human health consequences, the study predicts. Some effects are potentially beneficial, such as expanding winter habitat for cold-sensitive manatees and sea turtles; others pose problems, such as the spread of insect-borne human diseases and destructive invasive species. 

Many parks are being impacted by invasive species, and not just those along the southern border. Some invaders were actually imported to the United States to help combat native species, such as Indian mongoose brought to Hawaii to battle rats in sugarcane fields, while others include domesticated species gone wild, such as donkeys and burros in such national parks as Death Valley, Grand Canyon, and Virgin Islands.

“I think all of the parks are at risk for invasive species, and this is regardless of whether or not it is a park whose mission is focused on natural resources or if it's a park whose mission is focused on cultural resources,” said Jennifer Sieracki, the National Park Service’s invasive animals program coordinator. “Invasive species will impact not only the environments, but also cultural resources, infrastructure, and public safety and health as well as wildlife health.”

In the coming months, a team of National Parks Traveler writers -- Rita Beamish, Patrick Cone, Kim O'Connell, and Lori Sonken -- will focus on problems invasive species have created in the parks, the economic toll they’ve exacted, and the efforts by the National Park Service and other agencies and stakeholders to slow the invasions and mitigate the damages they’ve created.

Burmese pythons just might be the poster child for invasive species in the National Park System/NPS

Invasive Species Are Not An Isolated Problem

While the Burmese python invasion of Everglades National Park arguably is the most well-known problem facing the Park Service, it’s far from the only one. Northern snakeheads, lionfish, lake trout, cheat grass, and feral swine are among the park system's many invaders. There also are invading rats, insects, sheep, lizards, trees, and marine creatures. And they’re a threat not only to the parks’ natural resources and native species, but to cultural resources, as well.

“A big issue in the Southeastern United States parks are feral swine,” said Sieracki. “And of course, we've heard all of the issues about feral swine with natural resources where they cause erosion in river streams, and they dig up plant species, some of those being threatened and endangered. But they also do considerable damage to cultural resources. I know at Ocmulgee Mounds National Historical Park, they will dig up the earthworks that are there. I believe Congaree National Park also has similar issues.”

Cumberland Island National Seashore is among the park system units with feral swine/NPS file

Across the system, invasives are overwhelming native species, increasing fire hazards, and even attacking buildings. At Fort Pulaski National Monument in Georgia, vegetation growing on the walls of the fort is slowly damaging the mortar. Some invasive species are restricted to a region, while others find themselves at home across the nation.

“There are a few species that cross the United States. But there are some species that are incredibly problematic on a regional basis, like cheatgrass in the West,” said Terri Hogan, who monitors vegetative invasives for the Park Service.

Regional invasives include tamarisk and Russian olive in the Southwest, and knotweeds elsewhere that undermine roads, bridges, and building foundations, she pointed out.

“There are a number of species that are hard to control, relatively widespread, and really change the environment once they're introduced,” Hogan added.

Among the agencies and companies working with the National Park Service on the invasive species problem is Cardno, a global engineering and environmental consulting company that has worked with the Park Service on a variety of issues in dozens of parks, including Yosemite National Park, where it helped with the restoration of the Merced River corridor through the park's iconic valley.

Some invasive species stand a better chance of being beaten back than others, said Ron Rudolph, the company’s vice president for business development.

“In terms of the ability to eliminate invasive species, I think that would be a fool's errand, as evidenced by the proliferation of a number of pernicious species, particularly in the West,” said Rudolph. “And I don't see any way for them to be eliminated, possibly ever. You could also look at the Everglades, an explosion of invasives. There, I think the best we can do is control them. And in the absence of that, they will continue to proliferate and dominate the environments, which undermines the basic tenets of the National Park Service Act, which is to protect and preserve the parks unimpaired for future generations.”

Climate Change Is Aiding Nonnative Species

The challenges across the Park System are myriad, and in many areas climate change is aiding the invaders as warmer temperatures make ecosystems more conducive to nonnative species, both plant and animal, and in some cases allow species to move into areas that they previously didn't call home. In Hawaii, for instance, disease-carrying mosquitoes threaten to kill off species of endangered birds in national parks.

Household pets gone wild, such as this feral cat at Santa Monica Mountains National Recreation Area, also are an invasive problem in some parks/NPS file

And then there’s the question of whether the Park Service has the necessary resources (funding, personnel, and technology) to mount a significant challenge to invasives. Has the agency prioritized the threats of invasive species and developed a strategy for battling them, focusing on invasives that most threaten endangered and threatened native species?

At the U.S. Geological Survey, staff is collaborating with the Park Service on work to predict where invasive species might show up in the park system, how climate change is influencing invasions, and even biological means for attacking invasives. But the general public can play an important role, too. Being able to detect the arrival of an invasive species and react quickly to its appearance is critical, said Hogan.

“That's where we get the biggest bang for our buck. If we can educate the public, and actually internally, our employees, about what they can do to prevent spreading species, that's where we're going to make the biggest difference,” she said. “So, it's those new species, or moving species from one place to another.

“We're working with USGS to develop a prioritization tool to help parks better home in on the species that they have the potential to control, or that pose the greatest threat to the resources that they are protecting,” added Hogan. “And for plants, we have had invasive plant management teams out in the park since the 2000s.”

Park Advocates Contribute Dollars To The Effort

Support also is coming from the National Park Foundation, where donors have brought dollars to the effort.

"It's a strategic but significant investment in helping the Park Service on many different types of invasive species issues that parks face," said Jason Corzine, a vice president at the foundation who focuses on natural resource issues in the park system. "We've been working on this issue for many years. As we think about our landscape and wildlife work, invasive species are just an embedded part of that work. It's really a natural fit in the wildlife and conservation work we do as a foundation. And again, as we think about climate issues, it all kind of dovetails nicely."

Nonnative tamarisk trees, which can suck up 200 gallons of water a daily, are a problem at White Sands National Park and many other units in the park system/NPS file

For example, the foundation has financially supported, along with Yellowstone Forever, efforts to reduce nonnative lake trout populations in Yellowstone to help native cutthroat trout numbers rebound. At Voyageurs National Park in Minnesota, the foundation has supported efforts to remove invasive hybrid cattail vegetation from 1,016 acres of wetlands on Rainy and Kabetogama lakes. 

Eradication of invasive species won’t come overnight, and it might prove impossible to fully remove some, as seems to be the case at Lake Powell. In some cases, controlling their populations might be the best solution.

Also unknown is the eventual cost the Park Service will incur in striving to minimize the impacts of invasive species. In Fiscal Year 2020 alone the agency had a $143 million budget to address the problem. Whether the total cost over time eclipses the often-touted $12 billion or so in backlogged maintenance needs in the park system remains to be seen.

"The issue is not going away," Corzine said. "It's going to be a presence within the Park Service. I look at each of these parks as a unique kind of learning laboratory, with climate issues in general, invasive species issues in general. I don't know that they've ever put a pen to paper to say, 'This issue in particular is costing us X dollars a year in perpetuity.' I just don't know that they've approached it that way in a very holistic sense.

"I think they've got science and the expertise in-house where they are thinking about this but at a global picture, I'm not sure if they know the real financial impact that this presents to the Park Service and the visitor experience, ultimately," he said.

In the coming months, the Traveler will be examining this issue in parks across the country, with a focus on invasive vegetation, animals, and fish, along with stories that look at the economic toll, technologies being used in the battle, and a look at success stories.

This series is made possible in part through the support of Cardno.