Bipartisan legislation has been introduced into the U.S. Senate asking the National Park Service to "increase the use of native plant materials on lands it cares for," but will climate change make those landscapes inhospitable for the natives and more suitable for invasives?

It's not an unreasonable question. Put another way, "How long does it take a non-native to become a native" in the National Park System?

Look across the park system and already you can see the relevance of that second question in many places.

• Along the Yampa and Green rivers in Dinosaur National Monument in Utah and Colorado, and along the Green and Colorado rivers through Canyonlands National Park, also in Utah, tamarisk, aka salt cedar, is a decorative tree native to Eurasia and Africa that is flourishing and which can overtake native cottonwoods and willows without hard work to stop its spread.
• At Everglades National Park in Florida, Melaleuca is a subtropical tree native to Australia, New Guinea, and the Solomon Islands that arrived in South Florida in the early 1900s for, the Park Service says, “swamp drying.” Unfortunately, the tree spreads quickly, pushes out native species such as sawgrass, and is a risk to the park’s marshes, wet prairies, and aquatic sloughs.
• At Santa Monica Mountains National Recreation Area in California, so invasive are non-native weeds that the Park Service has recruited volunteers to pull them out.
• Garlic mustard is among the exotic species growing along the Appalachian National Scenic Trail.

The list goes on and on. Some of the species were intentionally brought in by humans for some task, and anchored themselves to the landscape. Others might have drifted in on the winds. Against this sort of dilemma, Sens. Susan Collins, R-Maine, and Maria Cantwell, D-Washington, recently reintroduced legislation to promote the use of native plants. The Native Plant Species Pilot Program Act would encourage the National Park Service to increase the use of native plant materials on lands it cares for.

“This bill will ensure that we preserve Maine's cultural history and natural heritage,” said Senator Collins in a release.  “Acadia's native plant communities includes many species such as the blueberry barrens near the mountain summits, the towering white pines in older forests, and the cranberry bogs along Northeast Creek that contribute to Maine’s iconic landscape. Other native plants in Maine are the wildflowers that bloom in August and September, such as asters and goldenrods, helping to attract the more than 3.5 million visitors a year to the seventh most-visited national park in the United States.”

Cantwell added that, "(B)ringing more native plants back to our shared public lands will help us combat invasive species, provide food and shelter for local wildlife, and adapt to the looming threat of climate change." 

In a press release, the senators pointed out some of the benefits of healthy native plant communities;

• Requiring fewer pesticides and fertilizers;
• Requiring less water and maintenance since they have adapted to local weather conditions;
• Providing shelter and food for local wildlife; and
• Preventing disruption to native wildlife and larger ecosystems.

But can their proposal succeed in the face of climate change? 

At Acadia National Park, Nick Fisichelli, is president and CEO of the Schoodic Institute, a nonprofit organization that conducts scientific environmental research. When I visited the institute, which is located on the park's Schoodic Peninsula, in 2019 for a workshop, Fisichelli was the forest ecology program director. Part of his work that summer was working to recover vegetation atop Cadillac Mountain that had suffered from the trampling of countless visitors' feet.

While the plants had learned to tolerate drought conditions in poor, thin soils that have been forming for thousands of years following the last glaciation and which dry out quickly, frigid winter temperatures, and glaring summer sun, they can't hold up against with trampling. 

"It can't handle it," Fisichelli told me as he showed test plots when botanists were trying to get plants to return. "With trampling, there's been loss of vegetation and the soils just blow away."

A long running project aims to restore vegetation that had been trampled atop Cadillac Mountain in Acadia National Park/Kurt Repanshek file

Some of the areas had been fenced off for 15 years, and "there really hasn't been measurable change," the scientist told me.

That work demonstrates just part of the challenge the senators' legislation, if enacted, might confront. In some parks, conditions are just so harsh that even getting natives to return is a challenge.

The other challenge could be competing with climate change.

"With climate change, we need to do a better job of recognizing that nature is dynamic and ever-changing, and what species are found where is also changing," Fisichelli told me last week during a Zoom call. "If you’re looking at the right timescale, trees are moving all over the map, so to speak, if you’re looking at it over 1,000 years. You can look at other species, birds are moving minutes to days across the map as far as their ranges go.

“It is also a dynamic system, so I think you have to layer those species on. It does make it a little more complicated, I think," he continued. "This dynamic of removing invasive species and the need in many cases to restore natives, and then you overlay this rapidly changing environment, hotter temperatures, more drought, more heavy rain events for this area of the country in the northeast, and thinking about which species to restore and where on the landscape.”

Sand bags work to shore up eroding soils from around vegetation atop Cadillac Mountain/Kurt Repanshek file

Fisichelli didn't dismiss the goal that the senators were chasing. 

“I think it’s part of a more holistic process that needs to be considered. I don’t know any of the details on this specific bill, and so I can’t speak to that. I certainly appreciate Sen. Collins and the others reintroducing this bill," he said. "I think this is one step towards climate-change adaptation. Reducing existing stressors is one important action, and so non-native species are a prime example of that. It’s tougher for native species to respond and adapt to the pressures of climate change when they have all these other stressors making their existence even more difficult. Sort of that multiplier effect.

“And so, from that standpoint it makes some sense. I think also just thinking about non-native plant management, eradicating non-native plants is a critical step in the process."

Part of the work Fisichelli showed me back in July 2019 were test plots where he was seeing what tree and plant species not native to Acadia might be able to thrive in the years ahead when the natives might be forced out by climate change.

Red spruce is "the most abundant tree species here, in Acadia. About 40 percent of the trees are red spruce, and it’s projected to lose half of its suitable habitat here in this region in the coming decades," he pointed out last week. "So, the question has been asked, where might it persist in climate refugia, and where is it going to struggle? Using that information, in addition to invasive plant management and restoration, to make decisions.”

The test beds on Cadillac, he reminded me, are part of the work "to figure out which species are going to struggle and which ones are going to do well. There’s lots of computer modeling, simulation modeling that’s been done, so we’re trying to build on that with on-the-ground experiments.”

The legislation being carried by Collins and Cantwell doesn't overlook climate change, and realizes that “of the 20,000 known native plant species in North America, it has been estimated that nearly 25 to 30 percent are at risk of extinction as a result of factors such as habitat loss, invasive species, temperature shifts, and pesticide use.”

The legislation calls for the Park Service to develop a pilot program that would "give preference to locally adaptive native plant materials and incorporate efforts to prevent the spread of invasive, non-native species. It would also authorize the Department of the Interior to conduct a study to determine the cost-effectiveness of using native plants."

Whether such a program can succeed in ensuring that today's natives are tomorrow's natives is questionable, though.

“A place like Acadia, relative to some other place, ecosystems are more intact. There are fewer non-native species; the load of non-native isn’t as high. But it is potentially the future," Fisichelli told me last week. “I say the future lies to the south. As conditions continue to warm, development that’s to the south comes to Acadia. That is going to be the future. And so, that’s why this more holistic management is really needed.”