Summer 2024

Do or Die?

By Elisabeth Kwak-Hefferan

As climate change threatens some of the national parks’ most treasured species, scientists ponder a drastic strategy: moving plants and animals into new habitats to save them.

One cold, rainy day in August of 2014, a handful of fisheries biologists fanned out across the braided channels of Logging Creek in Glacier National Park. Two of them wore boxy contraptions on their backs hooked up to hand-held wands — think the proton packs from “Ghostbusters” — which emitted an electric current meant to temporarily stun any fish swimming nearby. Slowly, methodically, they picked their way over deadfall and through thick brush, toting buckets and nets, covering every last inch of the stream. The going was tough, but the biologists pressed on for hours. After all, this was a rescue mission — and a pretty radical one at that.

Every time they found a stunned bull trout, a federally threatened species whose numbers have plummeted across the West, they scooped it into a bucket. Chilled hands measured the speckled fish’s length and weight and took a tissue sample from its fin for genetic analysis. After scouring the creek for 16 days, they put 111 bull trout they had collected, all juveniles, into two waterproof backpacks full of oxygenated water. Clint Muhlfeld, a research aquatic ecologist for the United States Geological Survey Northern Rocky Mountain Science Center, shouldered one of the 45-pound packs and started hiking past the waterfall at the top of Logging Creek and on to Grace Lake. “We knew we’d only have one shot at this,” he said. “I was thinking, ‘If we do nothing, the writing is on the wall. We’re going to lose this population that represents thousands of years of Glacier’s natural heritage.’”

The crew placed the packs in the creek that flows into Grace Lake and let the trout acclimate to the colder water for several minutes. Bull trout had never lived in Grace Lake before, but the biologists unzipped the packs and let the bullies swim out, watching as the fish disappeared into the unknown waters of an entirely new habitat.

The Glacier bull trout project is thought to be one of the first uses in a national park of a controversial conservation strategy called managed relocation (also known as assisted migration or conservation introduction). In simple terms, it means moving a species to a new location to protect it from the effects of climate change and invasive species. The scope of these relocations varies widely, from a nearby move well within a species’ current range, as is the case with the bull trout effort in Glacier, to the transfer of a plant or animal beyond the boundaries of its historic range.



Flora and fauna have always shifted their habitats as global conditions changed. Animals use their legs, fins or wings to move; plants produce seeds that are carried into new territories by breezes or animals. But as climate change warms the world rapidly — heating rivers, shifting rainfall patterns and erasing snowpack — scientists fear some species won’t be able to keep up by moving to more hospitable areas or evolving to adjust to different conditions. “Assisted migration is an attempt to mimic range changes that would have naturally occurred when the rate of environmental change is on a geologic time scale,” said Jay Goodwin, vegetation branch chief at Joshua Tree National Park. “Anthropogenic climate change is happening in the blink of an eye, comparatively.”

Land managers have other tools to help creatures move, such as conserving enough contiguous land to create wildlife corridors, building passages for fish and other aquatic animals around dams, culverts or levees, or removing those. When such measures fall short, though, scientists are increasingly considering managed relocation for at-risk animals and plants. But the idea flies in the face of what’s been the prevailing approach to conservation and stewardship for more than a century: protecting nature largely means leaving it alone.

To do it right is going to be very, very difficult.

Today, managed relocation is controversial among scientists and environmental advocates alike. Moving species to entirely new places — “playing God,” some argue — is a step far beyond the reintroduction of plants or animals to their historic habitats (such as bringing wolves back to Yellowstone National Park). To start, the whole endeavor is a big question mark. Elaine F. Leslie, who retired from her role as chief of the National Park Service’s biological resources division in 2019, points out that species such as saguaro and Joshua trees are part of a complex web of interactions between mammals, reptiles, birds, invertebrates, microfungi, bacteria and other organisms that we don’t fully understand. “Those are whole ecosystems in themselves,” she said. For just one example, “I don’t think we know enough about the soils to be able to properly strategize for successful relocations.”

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And in the past, humans moving species — intentionally or not — hasn’t gone so well. Examples abound of nonnative species wreaking havoc on their new ecosystems, and national parks are not immune. A Japanese insect called the hemlock woolly adelgid that hitched a ride to the U.S. on imported trees has been killing swaths of hemlocks in Great Smoky Mountains and Shenandoah national parks, and mongooses brought to Hawaii to feast on introduced rats ended up decimating the islands’ birds, such as Hawai’i Volcanoes National Park’s nēnē goose. In 1915, Crater Lake National Park added nonnative signal crayfish to the lake as a food source for nonnative fish, and the crustaceans have almost wiped out the Mazama newt, which doesn’t exist anywhere else.

Well-intentioned park managers have gotten it wrong before, and that’s bound to happen again, said Dan Simberloff, an ecologist and a professor of environmental studies at the University of Tennessee and a prominent critic of managed relocation. There are simply too many unknowns about how a relocated species would interact with the countless other species in its new habitat, he said. “To do it right is going to be very, very difficult.”

Even if a managed relocation did work out well, Simberloff added, the strategy isn’t a realistic solution to address the full scope of the problem. “There are thousands and thousands of species whose range and persistence are threatened by climate change,” he said. “To do this right would take a huge amount of work for any one of them.”

Indeed, due to practical constraints that include limited funding, scientists will be forced to pick just a few species to try to save — and the chosen ones will probably be high-profile, beloved plants and animals such as sequoia trees and Hawaiian honeycreeper birds, said Mark W. Schwartz, professor emeritus at the University of California, Davis. “When it gets down to this particular salamander or that lousewort, we won’t have the time and bandwidth to do it,” he said.



The question Schwartz and others grapple with is: Is it better to save a few than none at all? “I wish we lived in a world where we didn’t have to do this,” Schwartz said. “It’s a terrible idea that we don’t want to do, but as we see climate change and invasive species having impacts, our choice may be to stand by and watch something go extinct, or at least try, and take the risk that it has a negative impact on its new location. There’s no way to be 100% certain. All you can do is try to minimize risks.”

In one of the first known instances of managed relocation — and one that was unsupervised by any government authority — a group of concerned citizens started planting an endangered conifer species well north of its Florida range in the mid-2000s. In recent years, a similar group has helped plant redwoods in city parks in Washington and Oregon, beyond the trees’ current range. And we may be on the brink of a new era of species management — particularly in national parks, with their vast tracts of wild land and mandate to protect natural resources.

In 2020, the Park Service published a new framework for decision-making in a time of swift ecosystem changes. Called Resist-Accept-Direct, the tool asks managers to consider those three options when responding to threats to ecosystems: resist the change by fighting to maintain current conditions, accept it without intervention, or direct the change toward a preferred new outcome. Managed relocation falls squarely under the “direct” option, and a few months later, the Park Service issued a separate risk-assessment tool for park managers considering the strategy. The guidelines specifically address populations of flora and fauna that are threatened with extinction because of climate change or invasive species, many of which outcompete native species in warming conditions. The report walks managers through a decision-making process that weighs critical questions, including whether such a move can be justified ecologically and if its attendant risks are acceptable or not. In another significant move, the U.S. Fish and Wildlife Service updated an Endangered Species Act rule last summer to allow for the introduction of species outside their historic ranges.

In the years leading up to the Grace Lake bull trout project, Glacier scientists had become increasingly concerned about the native fish’s survival. Invasive lake trout, introduced to the watershed more than a century ago for angling opportunities, had been steadily spreading into the lakes and rivers that historically supported bull trout. One by one, bull trout populations faded away — outcompeted and straight-up eaten by the lake trout.

Watch the video to learn more about the bull trout project. camera icon NPS

That immediate threat was the principal driver for the bull trout relocation project, but biologists also had climate change in mind. “Bull trout is the canary in the coal mine for climate change, because it has the coldest water-temperature requirement for any salmonid in the Northwest,” Muhlfeld said, adding that the park includes a number of clean, cold bodies of water where bull trout can likely thrive even as temperatures rise. “Those are critical refugia for trout and other species under climate change,” he said.

The relocated bull trout have survived so far. But Chris Downs, aquatic and physical science programs leader for Glacier, cautions that it’s still too soon to declare victory at Grace Lake. “These projects take a long time to evaluate,” he said. “The fish have to grow, mature and breed.” Still, the park has continued down the same road: In 2019, biologists stocked native westslope cutthroat trout in Camas and Evangeline lakes after killing the area’s nonnative fish species with rotenone, a pesticide. Beginning later this summer, the team plans to start introducing bull trout, westslope cutthroat trout and mountain whitefish to Gunsight Lake, a cold body of water sitting just east of the Continental Divide that had been stocked with invasive rainbow trout. “I think these things are fairly low risk,” Downs said. “It seems like there’s a lot more potential upside than downside.”

Downs, Muhlfeld and other researchers developed a framework to use for evaluating proposed fish relocations before proceeding with them. The guiding principle of the document (which they published in the North American Journal of Fisheries Management in 2016) is “first, do no harm,” but it also spells out important questions for scientists to consider: Can the recipient habitat support the new species? Are the creatures already living in the new habitat compatible with the relocated species? Will the relocation introduce diseases or parasites to the new habitat? What effect will relocation have on the donor population? And will the new habitat remain suitable as the climate continues to change? “We did the homework, we established a scientific framework, we collected the information for the managers to base their decision on,” Muhlfeld said. “The Grace Lake option checked all the boxes in that framework.”

Bull trout is the canary in the coal mine.

The Park Service’s ecological risk-assessment tool — which was developed for any species, not just fish — looks at similar questions. It identifies six major areas of risk, including risks to the target species, risks to the recipient ecosystem and its organisms, risk that the relocated species could become invasive, and risk to culturally or economically important species (such as a bird considered sacred by an Indigenous Tribe, or a fish that’s harvested commercially). Crucially, it also asks managers to consider the risk of doing nothing. “The cost of no action is that at Glacier National Park, in some time window very soon, we’ll lose this genotype” of bull trout, said Gregor Schuurman, an ecologist with the National Park Service Climate Change Response Program. “And we’ll fail to carry out our mission of conserving resources unimpaired.”

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Other park managers across the country are thinking about similar moves. At Joshua Tree, in Southern California’s Mojave and Colorado deserts, scientists worry about the park’s iconic namesake. Climate models predict that intensified drought and drier soils will make it impossible for western Joshua trees to survive in much of the park by 2100. Managers have already begun to plan for such a future — they’re considering the possibility of planting Joshua trees in cooler areas outside the park where they don’t currently grow. But to be able to do that, they need seeds.

In April of 2022, park scientists watched anxiously as the park’s Joshua trees bloomed. These plants — technically, they’re not actually trees but members of the agave family — don’t produce seeds every year, but as spring slipped into summer, white clusters of flowers gave way to bundles of light green, mango-sized fruits across the park. Managers needed to move quickly to harvest the ripe fruits before rodents and ravens ate them all. A crew from the local Urban Conservation Corps program and staffers fanned out among the Joshua trees, wielding telescoping painting poles with hooks on one end. The crews stretched those hooks into the treetops, plucking and gathering the mature fruits. After two weeks of work in triple-digit temperatures, they’d collected more than 800,000 seeds representing 14 different populations. (Unfortunately, the “dry site” trees, which might be best adapted to life in a hotter, drier future, didn’t produce seeds in 2022, as drought prevented them from fruiting.) The seeds that were harvested became the park’s Joshua tree seed bank. “It was the first time the park collected them with the goal of conserving genetic diversity across the species within the park,” Goodwin said.

The seed bank will support projects to plant Joshua trees in areas of the park, including existing burn zones, that have the potential to be refugia in the future, but it might also be the start of a managed relocation. Goodwin acknowledged that any such project would require much more study and buy-in from other land managers, but he said the intent of the seed bank is to have genetic diversity for future options. “That could include moving Joshua trees to locations outside the park, where they may not have existed,” he said, or even breeding more drought-resistant plants as is done with commercial crops.

At Acadia National Park, managers are experimenting with the technique as a way to preserve the health of the whole ecosystem, rather than to save a particular plant. “We’re thinking about, ‘What are the characteristics that are important for the ecological integrity of a place?’” said Abe Miller-Rushing, the park’s science coordinator.

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Invasive shrubs such as glossy buckthorn and Japanese barberry have become a major problem at Acadia, aggressively outcompeting native species in part because they leaf out earlier or hold on to their leaves longer, taking more than their share of the sunshine. Scientists fear not only that a warming climate will eventually kill off Acadia’s boreal forest, but also that invasive shrubs will take over. “An invasive shrubland has a lot of characteristics that we’re not excited about,” Miller-Rushing said. “It would really fundamentally change the park even more than we would expect due to climate change alone.”

If the goal is preserving a forest ecosystem at Acadia — even if it’s composed of different trees than the ones that currently thrive there — then one approach could be planting native species from farther south. “Bringing plants up that already know how to take advantage of a longer growing season could potentially help occupy that niche,” Miller-Rushing said, “and reduce the chances of invasive plants reinvading.” The idea is that these transplants could shade out the nonnatives, buying time for native tree species such as oak and hickory, as well as all the other organisms that make up a healthy forest, to migrate north on their own.

Acadia is taking baby steps now at two experimental plots at Bass Harbor Marsh and Great Meadow Wetland. Scientists are planting a variety of native plants that currently grow in the park, and they are hanging shade cloths over them. If shading turns out to be an effective way to suppress the invasives, then park staff might introduce southerly species such as coastal pepperbush to new test plots.


Cat O’Neil is an award-winning illustrator specializing in visual metaphor. She studied at Edinburgh College of Art and has lived in Hong Kong, London, Glasgow, Lyon and Edinburgh.

On Acadia’s highest summits such as Cadillac Mountain, managers are also looking to conserve native species through a related strategy called assisted gene flow in which scientists introduce genetic diversity to a threatened population (Sequoia National Park is doing the same thing as it plants seedlings in burned sequoia groves). “We want to make sure that we’re planting species and individual plants that are going to persist” in a hotter future, Miller-Rushing said. That could mean planting a species such as three-toothed cinquefoil that currently grows on these mountaintops — but using individual seedlings from a more southerly population of the same plant that already experiences warmer temperatures. “We hope, with that genetic diversity, somebody’s got the right traits for the climate moving forward,” he said.

Exactly how well managed relocation will work — how effective it will be in protecting threatened species as the climate warms — remains an open question. Also, are park managers’ money, time and efforts better spent on relocating species at risk or making their current habitats more resilient to climate change? (Indeed, the Inflation Reduction Act is pumping millions of dollars into resilience projects, from forest thinning and streambed rebuilding at Redwood National and State Parks in California to native tree plantings at Catoctin Mountain Park in Maryland.)

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For the Park Service’s Schuurman, it’s not an either-or question. Managed relocation is just one of the tools available to public land managers trying to address the impacts of climate change on the species in their care. “I can remember my former self from two decades back, who thought the idea of adapting to climate change was giving up on fighting the root causes of climate change,” he said. “I came to understand that you can’t just focus on mitigation, or you’re going to lose opportunities and resources. They go together.”

The hard truth behind the questions about managed relocation is that national parks are experiencing profound shifts, whether those who manage them move certain species to new territory or not. “What’s so important to keep in mind is: That recipient ecosystem is probably changing substantially anyway because of climate change,” Schuurman said. “Everything is moving.”

Miller-Rushing echoed that sentiment. “Acadia is already a very different place than it was 100 years ago,” he said. “Keeping it the same isn’t really an option.”

About the author

This article appeared in the Summer 2024 issue

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