Torreya Guardians
The Torreya Guardians is a self-organized group of conservationists dedicated to facilitating the assisted migration of the Florida torreya by rewilding it further north than its native range in Florida and Georgia. Founded in the early 2000s, the group is often mentioned as an instigator of the assisted migration of forests in North America for conservation and climate adaptation purposes. It is an example of citizen-initiated citizen science.
Background
The endangered Florida torreya
The Florida Torreya is an endangered tree of the yew family, Taxaceae, found in the Southeastern United States, at the state border region of northern Florida and southwestern Georgia.T. taxifolia'' became one of the first federally listed endangered plant species in the United States in 1984; the IUCN has listed the species as critically endangered since 1998. It is considered "the rarest conifer in North America." In 2010 98% of the mature trees of the species were believed to have been destroyed due to a poorly understood fungal blight as well as inundation due to dams and destruction by deer using trees as antler rubbing posts. In 2019 a staff biologist for the park in northern Florida named for this tree, Torreya State Park, spoke of this species as being "functionally extinct in the wild."
Climate change
Climate change is increasing the average temperatures of American forests. Forests in the contiguous United States have experienced a 0.8 °C increase since 1900. That some native trees already lag in northward range expansion was known in the 20th Century, and has increased during 21st Century warming. A classic paper by forestry scientist Margaret B. Davis was published in 1989 and titled, "Lags in vegetation response to greenhouse warming." She concluded, "To track climatic changes in the future, caused by the greenhouse effect, however, their range limit would need to move northward 100 km per °C warming.... Many species of trees may not be able to disperse rapidly enough to track climate, and woodland herbs, which have less efficient seed dispersal mechanisms, may be in danger of extinction." In 2020, the U.S. National Park Service began seriously considering how to adapt park ecologies to a rapidly changing climate—including helping iconic tree species to move upslope or poleward faster than they can do on their own. Action orientation by the agency was then shaped into the "Accept-Resist-Direct" strategy. A decade earlier, the U.S. Forest Service initiated experimental plantings for assisted migration of some of the most valued canopy trees in North America.Origins
The Torreya Guardians were founded in 2004 by Connie Barlow, an American science writer and amateur horticulturalist. The group is composed of citizens hailing from diverse professions, mostly based in the states of North Carolina, Tennessee, Michigan, and Ohio. Before their formation, they were searching for ways to better protect Torreya taxifolia from extinction. They worried that traditional conservation measures focused on rehabilitating the tree in its historical range were destined to fail, as well as being very expensive.Then, early members learned by visiting Torreya californica in forested sites in California, and through reports, that other trees of the Torreya genus would migrate to higher altitudes when warmer average temperatures put them at risk. They saw in this a solution to the plight of the Florida torreya, and hypothesized that the tree would thrive if relocated to lands north of its historical range. They argued that torreyas would be better suited to survive in a cooler climate and that the species in California often was found on very steep slopes.
Major American conservation institutions were unwilling to test their hypothesis. Plant assisted migration projects had never been implemented before in the United States for the purpose of conservation, so it was rejected. Instead, the United States Fish and Wildlife Service was trying to protect this species by managing the diseases affecting it in its native range at the time, with limited success.
Since the species listing in 1984, the official conservation efforts undertaken in behalf of the Florida torreya centered first on collecting and rooting cut branchlets from specimens in the wild. As those cuttings turned into shrubs, they were transferred into large pots or moved into managed horticultural plantings for genetic safeguarding until problems in the habitat itself could be discerned and corrected. Connie Barlow, on the other hand, believed that it made little sense to focus on finding a way to return torreya to its endemic habitat during a time of climate warming. Pointing to torreya's status as a glacial relict that had been unable to return northward after the glacial times ended, she expressed the need for citizen action in a 2010 article in Audubon Magazine. "Potted is the botanical equivalent of caged," she said. "I'm interested in preserving not just a species but its wildness."
The two sides had come to a head in 2004 when the environmentalist magazine Wild Earth published a pair of detailed pro and con articles on what to do about the Florida torreya. Connie Barlow and paleoecologist Paul S. Martin wrote the essay in favor of moving the species, citing evidence that the Florida torreya had been pushed south during the previous ice age. When the ice retreated, this large-seeded, subcanopy tree had trouble migrating back north to cooler realms. For most of its history, therefore, this species of genus Torreya had not been native to Florida. Mark W. Schwartz, an American conservation biologist who had been researching and participating in the preservation of the Florida torreya within its native range since 1988, wrote the piece opposing the assisted migration proposal. He was particularly worried about the precedent that citizen-led assisted migration of the endangered tree would set, the risk that even an endangered plant might become invasive in a different ecosystem, and the possibility of spreading the diseases afflicting the tree in Florida. These concerns were shared by Jenny Cruse-Sanders of the Atlanta Botanical Garden, who cautioned as well that the horticulturally derived seedlings planted by the citizen group might be genetically inferior to the wild genetics that her institution is safeguarding in ex situ plantings in Georgia.
Implementation of assisted migration
Action by Torreya Guardians in translocating an endangered tree poleward has been called "the best documented case of a managed relocation."While still a rare practice by conservation institutions, planting trees outside their native range is not illegal in the United States. Indeed, the horticulture trade has long been engaged in selling and planting both native and exotic plants with no legal limitations, except where governments have officially listed particular plants as invasive species in the United States. While endangered plants native to the United States have more stringent controls than other plants, commercial nurseries can sell properly sourced specimens so long as the sale is not across state lines. Provided there is no monetary transaction, private citizens can legally carry or send horticulturally sourced specimens of listed endangered species. The nascent Torreya Guardians took advantage of this legal exception to the Endangered Species Act to implement their own assisted migration project outside established institutions.
The Torreya Guardians saw North Carolina as particularly hospitable for the Florida torreya because trees of this genus have lived at the Biltmore Gardens, in nearby Asheville, for almost a century. Here can be found the second oldest surviving grove of horticulturally planted trees. In 2005 the Biltmore Gardens donated 110 seeds to Lee Barnes, a member of the Torreya Guardians. Most of the seeds were donated to horticultural staff of botanical gardens northward. Three years later, the group purchased potted seedlings from a nursery in South Carolina, and then drove the plants to two sites in the mountains of North Carolina, where the torreyas were planted into regrowth forests on private lands. Such in-forest plantings represent the group's emphasis not just in preventing extinction but also in re-integrating—that is, "rewilding"—this subcanopy species into native forest ecologies of the eastern United States.
In subsequent years, seeds or potted seedlings were also given to planters in additional eastern states, and as far north as Wisconsin, Michigan, and New Hampshire. Several volunteer planters are trained as professional ecologists or foresters, but most have acquired horticultural skills outside of a profession and are eager to assist an endangered plant. The volunteer in Cleveland, Ohio, Fred Bess, is a professional landscaper, and in 2017 his grove produced a handful of seeds. By 2023, more than a thousand seeds were produced annually, thus setting the record for the farthest north seed production in a fully outdoor setting.
In 2013, a journal article published in Conservation Letters described the actions of Torreya Guardians as a form of "citizen-initiated assisted colonization." The authors explained that the Endangered Species Act, while prohibiting citizen initiatives pertaining to imperiled animal species, "has encouraged citizens to undertake plant conservation, especially for charismatic plants threatened by climate change." Torreya Guardians was then described as having "established private experimental populations on the property of cooperative landowners to help preserve the species outside of its historic range because of its decline, lack of federal funding, and the availability of privately owned and commercially available plants and seeds."
Four law review articles published between 2009 and 2017 concluded that the Endangered Species Act of 1973 need not be amended to use assisted migration in species recovery. The citizen actions by Torreya Guardians in moving an endangered plant substantially northward of its native range remained an outlier to the official endangered species policies until June 2023. It was then that regulations governing the parameters of recovery plans were amended "to reduce the impacts of climate change and other threats such as invasive species." Deletion of "historical range" as a location parameter for "experimental populations" effectively authorized assisted migration for listed species. A press report on the regulatory change mentioned the citizen actions of Torreya Guardians as having preceded the official shift in willingness to consider northward experiments for other endangered species. Following the regulatory change, another journalist wrote that the "aggressive approach to conservation" by the Torreya Guardians "featured prominently in numerous scientific articles that followed, discussing the pros and cons of assisted migration."