At the Brink of Extinction
"Based on fossil records, we can speculate that the geographical range of T. taxifolia included North Carolina and perhaps, it was forced south by glaciers, and when they retreated, it became isolated in small areas of the southeastern United States." p. 12 of "Torreya taxifolia (Florida Torreya) 5-Year Review: Summary and Evaluation", 2010, U.S. Fish & Wildlife Service
"The species may be restricted to the area because it failed to migrate northward at the end of the Pleistocene." p. 6 of the first "Florida Torreya Recovery Plan", 1986, U.S. Fish & Wildlife Service
"Paleoecology and the Assisted Migration Debate: Why a Deep-Time Perspective Is Vital" online essay by Torreya Guardian Connie Barlow, February 2011.Connie Barlow (with assistance from Russell Regnery) has posted a short, 11-point summary essay that aggregates the data and develops strong scientific reasoning in favor of assisted migration for Torreya taxifolia. The essay also advocates a shift in the foundational paradigm from assuming 1491 is the proper time-standard for assessing native range to a "deep-time" perspective grounded in a paleoecological understanding that native ranges for all plants in temperate latitudes of the Northern Hemisphere have undergone substantial altitudinal and/or latitudinal migrations that have tracked changes in climate during the past several million years of Pleistocene glacial and interglacial cycles.
LEFT: Apalachicola River in January, in Florida's Torreya State Park
In the 1950s, Torreya taxifolia suffered a catastrophic decline, the ultimate cause of which is still unexplained. By the mid-1960s, no large adult specimens which once measured more than a meter in circumference and perhaps 20 meters tall remained in the wild, felled by what seemed to be a variety of fungal pathogens.
Today, the wild population persists as mere stump sprouts, along the Apalachicola River of the Florida panhandle, cyclically dying back at the sapling stage, such that seeds are rarely, if ever, produced. T. tax thus joins American chestnut in maintaining only a juvenile and diminishing presence in its current range.
WIKIPEDIA ENTRY (as of September 2018).EXCERPTS: This was one of the first federally listed endangered plant species in the United States in 1984. It is a Critically endangered species on the IUCN Red List, due to estimated 98% decline in mature individuals since the early 1950s. Before the start of the decline, the population was estimated to have been more than 600,000 (ca.1950). The current population is estimated to be between 500 and 600 trees, of which less than 10 are known to produce male or female cones. Its total extent of occurrence is estimated to be about only 200 square kilometres (49,000 acres). IUCN population viability analyses indicate that extinction within its native range is inevitable.
... Up to 11 species of fungi attack Torreya taxifolia, including species of Physalospora and Macrophoma. Fungicide treatment has been shown to be effective for fungal infection, with plants showing renewed growth after treatment. Recovery of the species may be inhibited by postglacial global warming, as it is best adapted to the cooler, moister climate found in this area during the last ice age. It may not have been able to move north in the postglacial warming, due to poor dispersal abilities.
Some biologists have suggested that Torreya taxifolia is an evolutionary anachronism similar to the avocado (Persea americana), Osage orange (Maclura pomifera) and Kentucky coffeetree (Gymnocladus dioicus), which was dispersed by a now-extinct animal. Similar to the Kentucky coffeetree (Gymnocladus dioicus) and Honey locust (Gleditsia triacanthos), the seeds of Torreya taxifolia are extremely hard and require scarification to germinate, which may have been performed by the process of passing through an animal's digestive tract. The terpene content of the berries and the thinness of the seed's shell imply that the extinct ecological partner may have been a large tortoise. ...
EDITOR'S NOTE: Endnote 6 (above) links to: Barlow, Connie (2000). "Anachronistic Fruits and the Ghosts Who Haunt Them" (PDF). Arnoldia (Volume 61, Number 2). Barlow is the founder and webmaster of Torreya Guardians.
Access in PDF the official USFWS ESA plan (updated summer 2010) for managing this endangered species, for which, "Given the lack of seed production in the wild and potentially a decline due to a disease, all population viability models predict extinction." (p. 11)
The original (1986) recovery plan provides more details on paleoecology and the harsh 20th century species decline than does the current plan. "Florida Torreya Recovery Plan", 1986, U.S. Fish & Wildlife Service.
Torreya taxifolia entry on the USF&WS webpage listing endangered species managed by the Panama City FL office of USF&WS. Full text:Torreya taxifolia Arn. is a dioecious evergreen conifer endemic to the ravine slopes on the eastern bank of the Apalachicola River in northern Florida and in parts of Georgia. Prior to 1950's, T. taxifolia was estimated to be the seventh most abundant tree species within Apalachicola Bluff regions. Surveys conducted in areas with known high tree densities suggested that T. taxifolia has lost at least 98.5% of its total population size since the early 1900s, causing the species to be federally listed as endangered in 1984. The loss of T. taxifolia is thought to have primarily been a result of fungal pathogens during the 1950s and 1960s, or a combination of environmental stress and native pathogens, but studies have yet to provide an explanation for this species' decline. Despite the conservation actions to protect and determine the cause of this species' decline, the degree of threat to its persistence remains high; therefore the threat of extinction that faces T. taxifolia is imminent.
For more details see Florida torreya 5-year Review: Summary and Evaluation and Root and Soil-borne Oomycetes and Fungi Associated with Torreya taxifolia
Access in PDF a 2013 paper (by L. Vargas and V. Negron-Ortiz) on soil fungi and potential root pathogens of T. taxifolia in its historically native range.
1962: "The Florida Torreya: Efforts to Preserve It" letter by W. A. Coldwell in Science.
Center for Plant Conservation: Profile of Torreya taxifolia. Note: This is a highly useful webpage, full of descriptions, records of species decline, ongoing communications of several botanical gardens on how to propagate, etc.EXCERPTS: Habitat - The taxon is an extremely rare conifer that once towered fifty feet above the forested ravines of the Apalachicola drainage system in northern Florida (Godfrey 1968, Foote and Jones 1994). An ancient genus of at least 160 million years old in age, species in the genus Torreya were widely distributed across the northern hemisphere during the Jurassic and Pliocene periods. Named for John Torrey, one of America's most distinguished botanists (1796-1783), this is one of the rarest native trees in the USA. Within its very limited range, it has become nearly extinct. There are no large trees left in its native habitats. What survives are a few scattered young saplings or suckers from root systems and bases of destroyed plants.
T. taxifolia is found in the understory of the rich hardwood hammock beech-magnolia and mixed hardwood forest (USFWS 1983, 1984, 1985). Canopy trees in these forests are mostly deciduous, but evergreen hardwoods and conifers are also common (USFWS 1986). This species can also grow on bluffs and woods along the Apalachicola, steep slopes of ravines (mid-slope) with nearly permanent seeps, and rises in calcareous bottoms. In Florida, Torreya species also occur in lower parts of ravine slopes and adjacent floodplains and prefers shady habitats with dark, moist sandy loam of limestone origin.
... Endemic to about a dozen ravine complexes along the Apalachicola River in Florida and adjacent Georgia, this species was once common. However, since the late 1950s, a fungal pathogen of uncertain origin and no known control has decimated the populations. There are currently no reproducing individuals known in the wild and the species is persisting only as stump shoots and occasional root sprouts. Most of the Georgia habitat was eliminated by flooding from a major dam.
...Karl Kern, Wyoming Nurseries in Cincinnati, OH supplied the Arnold Arboretum with plants of T. taxifolia. In 1962, Karl Kern said that they had a large specimen in the area that had survived perfectly. R. Allen, Calloway Gardens, Pine Mountain, GA 31822, collected seeds in Florida in 1981 for the Arnold Arboretum. Barry Yinger, York Haven, PA (Curator of Asiatic Plants, National Arboretum) in 1983 mailed cuttings from his plant, which, as he stated, had survived -17F in York Co., PA. The plant had originated from Semmes, Alabama. Rob Nicholson and Ida Hay in 1985 collected cuttings for the Arnold Arboretum north of Chattahoochee and in five places in Torreya State Park, Florida.
In a 1990 article in Natural History magazine one of the original participants in the 1990s branchlet-rooting program to prevent species extinction assembled knowledge then-known about the possible ultimate cause of Torreya taxifolia's sudden collapse to a variety of seemingly native pathogens. Access a reconstructed pdf of the original article here:• Chasing Ghosts: The steep ravines along Florida's Apalachicola River hide the lastsurvivors of a dying species, Torreya taxifolia
by Rob Nicholson (of the Botanic Garden at Smith College, Massachusetts)
EXCERPTS CONTINUE: "... The Apalachicola Bluffs and the ravines that dissect them are at the cusp of the deciduous woodlands and the lush subtropical jungle. It is an undecided forest, its luxurient ecotone having been shaped by the forces of glaciation during the Pleistocene era. As a New Englander used to deciduous woods, I was unsettled by seeing beech, maple, and hickory mixed with bold fan-leafed palmettos, spiky yuccas, and huge evergreen magnolias.
EXCERPTS: "... All the unknowns confound any recovery plan. Is Torreya an early victim of global warming and a precursor of a new wave of inexplicable extinctions? Has local land use destroyed this Torreya habitat? Is there any point in trying to fortify existing populations by replanting if a virulent pathogen lurks unchecked? Will propagations of cuttings from existing wild trees carry a new pathogen wherever the new trees are distributed? Or, frozen by doubt, will plant scientists do nothing while the unique species slips away, tree by tree?
"... In June 1989 I joined Mark Schwartz and we surveyed as many ravine systems as possible, carefully mapping and labeling the plants growing there.... When we returned in the fall, we collected small cuttings, tissue samples, and soil samples for genetic, propagation, and pathological studies. Alarmingly, in just a few months, a number of our mapped trees had been lost to deer rubbing, disease, and even falling limbs from the upper canopy. The species was going extinct before our eyes and will probably not last another generation.
"... More than 2,500 cuttings were collected from 166 trees and were treated with a variety of hormones to promote rooting. These were brought to Harvard's Arnold Arboretum, where 2,100 were successfully rooted and potted. The accession number of the sampled trees follows each of these clones (and any subsequent propagations) with the particulars as to the plant's original location in the wild. Therefore, in the distant future, ravines might be replanted with the same genetic material that once grew there. Cuttings taken from the wild five years ago are growing well and so far show no signs of disease. "... While the few remaining saplings may outlast the blight, not many people who have seen the trees would wager their homes on it. More likely, clusters of trees, propagated from specific ravines, will be grown in botanical gardens, universities, preserves, and state parks. This Florida native, as evidenced by the few healthy trees in cultivation, seems to thrive on the southern slopes of the Appalachian Mountains and is more cold tolerant than its present range would suggest. Possibly an Apalchicola refugium can be re-created, an artificial Torreya forest where pollen can float, genes mingle, and the evolution of the past hundred million years can continue, even if it is in a pitifully discounted format."
1984 Federal Register establishment of Torreya taxifolia as endangered is now available online and it establishes this species as a Pleistocene relict. The first paragraph begins:
"An evergreen tree reaching 18 meters tall, Torreya taxifolia (Florida torreya) was first discovered in 1834 and formally described in 1838. The Florida torreya and other endemics of the Apalachicola River system have received much attention from scientists and local residents. The relictual nature of this area accounts for the presence of many unique species (James, 1967). During recent glaciations, species migrated southward by way of the Apalachicola River system, which served as a refugium during cooling periods. The Apalachicola River is the only Deep River system that has its headwaters in the southern Appalachian Mountains. With the receding of the glaciers, cool moist conditions persisted on the bluffs and ravines of the Apalachicola River after climatic change rendered the surrounding area much drier and warmer."
The 1984 registration continues: "All mature viable trees are located in botanical gardens and arboreta. The wild trees do not now have good long-term survival prospects. The initial focus of recovery will be to address controlling the disease. After the disease has been overcome, recovery efforts would address reintroduction of the species into the wild."
• While the Draft Environmental Impact Statement states that "the bluffs and ravines served as a refugium when northern species migrated southward during glacial times and today the area has a high rate of endemism and unique vegetation," it is clear that there was no intent (not even curiosity) about thwarting the lethal disease by moving Torreya northward to cooler climes. Rather, discovery of a curative approach culminating in "reintroduction" to its currently native range was the only desired outcome set forth.
See a detailed, old U.S. Forest Service page on Torreya taxifolia before "assisted migration" was even considered.
Note: As of 2016, the USF&WS webpage for the 10 listed plant species managed by the Panama City FL office mentions for Ribes echinellum that "disjunct populations may represent Pleistocene refugia, remnants of what was once widespread Tertiary vegetation." Yet on the same page no mention is made of the Apalachicola habitat of Torreya as being a refugium (as is well known to paleoecologists). Thus this key characterization was dropped from descriptions sometime after the 1984 federal register notice was published. Here is the brief description that now appears on the plant list page:Torreya taxifolia Arn. is a dioecious evergreen conifer endemic to the ravine slopes on the eastern bank of the Apalachicola River in northern Florida and in parts of Georgia. Prior to 1950s, T. taxifolia was estimated to be the seventh most abundant tree species within Apalachicola Bluff regions. Surveys conducted in areas with known high tree densities suggested that T. taxifolia has lost at least 98.5% of its total population size since the early 1900s, causing the species to be federally listed as endangered in 1984. The loss of T. taxifolia is thought to have primarily been a result of fungal pathogens during the 1950s and 1960s, or a combination of environmental stress and native pathogens, but studies have yet to provide an explanation for this species' decline. Despite the conservation actions to protect and determine the cause of this species' decline, the degree of threat to its persistence remains high; therefore the threat of extinction that faces T. taxifolia is imminent.However, on page 12 of the current recovery plan, paleoecological information is well provided:Fossil records of Torreya are limited to seeds, leaves, and secondary wood of the Upper Cretaceous (Boeshore and Gray 1936, Chaney 1950). The records indicated that the distribution of the genus in past geological times was much wider than the present distribution. A fossil named T. Antigua, which has some characteristics in common with T. taxifolia and T. californica, was described from the Mid-Cretaceous of North Carolina and was also collected near MacBride's Ford, Georgia (Boeshore and Gray 1936). Currently, Florida torreya grows naturally in three counties in Florida: Gadsden, Liberty, and Jackson. It is also found in southern Decatur County, GA, just north of Chattahoochee, FL. Based on fossil records, we can speculate that the geographical range of T. taxifolia included North Carolina and perhaps it was forced south by glaciers, and when they retreated, it became isolated in small areas of the southeastern United States.• Here is how the 1986 recovery plan for Torreya taxifolia (its first) speaks of its pre-glacial fossil distribution:
• "Steephead Salamander Search, and the Apalachicola's Ice Age Refugees", by Rob Diaz de Villegas, WFSU Ecology Blog, 16 November 2017 (contains many excellent photos)EXCERPTS: ... If you go back millions of years, before the ravines that you see are in place, you would have had a relatively large, flat, sandy plateau," says David Printiss. Printiss is The Nature Conservancy's north Florida program manager, overseeing the Conservancy's Apalachicola Bluffs and Ravines Preserve. "During the last glaciation," says David Printiss, "all species from the Appalachians were pushed southwards by the cold weather." These changes occurred over thousands of years, so everything from large tree species to little salamanders would shift their ranges as temperatures changed. When these Appalachian species found steep, narrow ravines with cool, flowing water, it felt like home. So when temperatures got warmer again, many northern plants and animals left behind small populations in ravines and slope forests. Some entire species remained here, and only here. And so we have an interesting mix of flora and fauna that makes steepheads unique. "We have the southern end of the distribution of species like mountain laurel that you wouldn't expect," says David Printiss. "And you have other species that you'd call glacial relicts. They were left behind, so their sister species are up in the Appalachians.... There are other [relict] species like the torreya tree that just simply could not run uphill fast enough and was left behind," says Printiss. "So its global distribution is Torreya State Park and the Apalachicola Bluffs and Ravines Preserve."
VIDEO: Site Visits to Florida's Endangered Torreya and Yew Trees
Connie Barlow presents 15 years of baseline photos and videos she recorded of Torreya taxifolia and Taxus floridana in their historically native range in Torreya State Park in northern Florida. Photos of spectacular California Torreya trees, recorded by Barlow in 2005, show the potential for Florida Torreya recovery efforts to strive for. Fred Bess shows (in 2014 video) 2 Asian conifers (Cephalotaxus and Cunninghamia) used in landscaping that are Torreya look-alikes. Paleoecological evidence that Florida's Torreya was "left behind" in its peak glacial refuge supports "assisted migration" actions.
EDITOR'S NOTE: This 1905 publication contains the first suggestion that Torreya's preferred habitat lies northward of its endemic Florida range. Access online the entire report.
Note that in this 1905 report, the author posits that"It is associated with a remarkable and somewhat extensive group of northern mesophytic plants, and the conclusion is irresistible that Torreya is a northern plant of the most pronounced mesophytic tendencies, and to be associated with such forms as the beech-maple-hemlock forms of our northern woods, our most mesophytic type of association."
PHOTO ABOVE: In 2013 AJ Bullard demonstrated on his Torreya taxifolia tree in Mt. Olive North Carolina that this species actually will produce both female cones (top branchlet) and male cones (middle branchlet) on a single individual. Lower left branchlet shows vegetative buds.
In an email to Lee Barnes on 9/29/16 Frank Callahan wrote of his mature Florida Torreya trees in Medford OR: "Both of these trees exhibit male and female 'flowers', which is unusual for this taxon."
"A Remarkable Colony of Northern Plants Along the Apalachicola River, Florida, and Its Significance"
by H. C. Cowles, 1905
Report of the Eighth International Geographic Congress
Held in the United States
"In this association one finds two of our most notable endemic plants Torreya and Croomia. It seems likely, then that we should regard Torreya taxifolia as a northern mesophytic left stranded to-day only in Florida.
"It presumably is one of the plants that failed to follow up the last retreat of the Pleistocene ice, and is preserved here perhaps because of exceptionally favorable topographic conditions."
Scientific Papers of Asa Gray, Vol II, 1841-1886", selected by Charles Sprague Sargent, 1889.
Editor's note: Genus Torreya is one of several plant taxa scrutinized by Asa Gray for the remarkably disjunct ranges including eastern Asia, eastern USA, and (to a lesser degree) California, along with fossil evidence in western Europe. Images below are drawn from his 1872 paper titled "Sequoia and Its History". These excerpts below will begin with p. 149 of the original document:... In the tertiary period, the geological botanists assure us, our own very Taxodium or Bald Cypress, and a Glyptostrobus, exceedingly like the present Chinese tree, and more than one Sequoia, coexisted in a fourth quarter of the globe, namely, in Europe! This brings up the question: Is it possible to bridge over these four wide intervals of space and the much vaster interval of time, so as to bring these extraordinarily separated relatives into connection? The evidence which may be brought to bear upon this question is various and widely scattered. I bespeak your patience while I endeavor to bring together, in an abstract, the most important points of it.
Some interesting facts may come out by comparing generally the botany of the three remote regions, each of which is the sole home of one of these genera, i.e., Sequoia in California, Taxodium in the Atlantic United States, and Glyptostrobus in China, which compose the whole of the peculiar tribe under consideration.
A few pages later Asa Gray offers a paleoecological explanation:"...My speculation was based upon the former glaciation of the northern temperate zone, and the inference of a warmer period preceding and perhaps following. I considered that our own present vegetation, or its proximate ancestry, must have occupied the arctic and subarctic regions in Pliocene times, and that it had been gradually pushed southward as the temperature lowered and the glaciation advanced, even beyond its present habitations; that plants of the same stock and kindred, probably ranging round the arctic zone as the present arctic species do, made their forced migration southward upon widely different longitudes, and receded more or less as the climate grew warmer ... so that different species of the same genus, as in Torreya, or different genera of the same group, as Redwood, Taxodium, and Glyptostrobus, or different associations of forest trees, might establish themselves each in the region best suited to their particular requirements, while they would fail to do so in any other. These views implied that the sources of our actual vegetation and the explanation of these peculiarities were to be sought in, and presupposed, an ancestry in pliocene or still earlier times, occupying the higher northern regions.Editor's note: For more detail on the fossil evidence of genera extant in eastern North America and eastern Asia, but now lost to Europe, access Asa Gray's 1878 paper "Forest Geography and Archaeology", republished in the same volume in pdf as above (Torreya is included in that paper.) I will close these excerpts first with a paragraph admirable for the breadth of knowledge and attention to deep-time mysteries that, alas, have gone missing among the credentialed in charge of the fate of Torreya today. Then, with a paragraph whose beauty and heart remind us of how diminished the human quest for knowledge became when "natural history" was left behind in favor of the more precise and quantitative inquiries of "science." A century and a half ago, Asa Gray wrote (p. 161):
"The genealogy of the Torreyas is still wholly obscure; yet it is not unlikely that the Yew-like trees, named Taxites, which flourished with the Sequoias in the tertiary arctic forests, are the remote ancestors of the three species of Torreya, no severally in Florida, in California, and in Japan...""... I must refrain from enumeration of the angiospermous or ordinary deciduous trees and shrubs, which are now known, by their fossil remains, to have flourished throughout the polar regions when Greenland better deserved its name and enjoyed the present climate of New England and New Jersey. Then Greenland and the rest of the north abounded with Oaks, representing the several groups of species which now inhabit both our eastern and western forest districts; several Poplars, one very like our Balsam Poplar, or Balm of Gilead-tree; more Beeches than there are now, Hornbeam, and a Hop-Hornbeam, some Birches, a Persimmon, and a Planer-tree, near representatives of those of the Old World, at least of Asia, as well as of Atlantic North America, but all wanting in California; one Juglans like the Walnut of the Old World, and another like our Black Walnut; two or three Grapevines, one near our southern Fox Grape or Muscadine, another near our northern Frost Grape; a Tilia, very like our Basswood of the Atlantic States only; a Liquidambar; a Magnolia, which recalls our Magnolia grandiflora; a Liriodendron, sole representative of our Tulip-tree; and a Sassafras, very like the living tree...."
"... I, for one, cannot doubt that the present existing species are the lineal successors of those that garnished the earth in the old time before them, and that they were as well adapted to their surroundings then, as those which flourish and bloom around us are to their conditions now. Order and adaptation did not wait for man's coming, nor were they ever stereotyped. Organic nature, by which I mean the system and totality of living things, and their adaptation to each other and to the world, with all its apparent and indeed real stability, should be likened, not to the ocean, which varies only by tidal oscillations from a fixed level to which it is always returning, but rather to a river, so vast that we can neither discern its shores nor reach its sources, whose onward flow is not less actual because too slow to be observed by the ephemera which hover over its surface, or are borne upon its bosom."
Excerpts from a detailed chapter on Florida Torreya (2015, by Kara Rogers, University of Arizona Press) are accessible at the google books site, page 101, for The Quiet Extinction: Stories of North America's Rare and Threatened Plants.
"By 2010, among wild populations of Florida torreya, only six plants were able to produce cones." Note: Several pages of detailed disease descriptions and experiments then follow.
"In 1955, officials at Torreya State Park, in the heart of Florida torreya habitat, reported a steep decline in the tree's populations. . . Seemingly overnight the situation had turned dire. Adult populations had been decimated, and there was no indication that the species was reproducing. Florida torreya, Kurz and Godfrey warned , was on the brink of extinction. . . . The disease seemed to be worse for trees that received full sunlight than for those in more shaded areas. But the result was still the same. . . The only individuals that were spared the disease were seedlings younger than six months. They presumably were started from seeds left behind by dead adults. By the 1990s, however, virtually all adult trees in the wild had been killed, and between 1,000 and 1,350 juveniles remained. Many young trees displayed symptoms of the disease, and over time their stems were killed off, one by one. The likelihood of their survival being prolonged depended in part on the size of their main stem. A larger main stem meant a more promising outlook, at least for a while. But once the main stem died or when a tree was down to three or fewer stems, each a foot and a half tall or less, death ensued.
"Possibly also affecting the survival of Florida torreya is damage to protective communities of mycorrhizal fungi that associate with Florida torreya. Nearly all of its mycorrhizal associates belong to the genus Glomus, which contains a number of species that help defend trees against root pathogens. The abundance of those fungi, however, appears to be greater among garden explants than among trees in native habitats. Wild Florida torreya currently inhabit heavily shaded areas, which, combined with the presence of disease, may limit the trees' ability to support beneficial mycorrhizal fungi.
Note: Several pages follow that detail current management projects attempting to restore Florida torreya in its historically native range. The remainder of the chapter highlights the work of Torreya Guardians, as imaged below:
2015 ADDENDUM by Connie Barlow:
Supplemental hypothesis on why Florida Torreya was "left behind" in its peak glacial refuge of Florida's Apalachicola River: Might Torreya taxifolia have become stranded in its peak glacial refuge, not so much because of the slow seed-dispersal capacities of squirrels (as hypothesized by Barlow here and here) but because of the absence of northward flowing rivers between Florida and the southern Appalachians? Barlow arrived at this hypothesis during a field visit to the largest remaining Torreya taxifolia in existence: the one along the Chattahoochee River, in the front yard of an historic-register home at the riverfront. (Click on video below.)
While visiting the sole remaining T. taxifolia in Columbus GA, Connie Barlow was struck by its location along a free-flowing section of the Chattahoochee River. The Chattahoochee is the main conduit between the peak-glacial plant refuge in n. Florida and the Appalachian Mountains. Might Torreya taxifolia have been "left-behind" in its Florida refuge because the Chattahoochee River flows southward? The tree could have dropped seeds into the river for a speedy journey south, but it would have been utterly dependent on the slower actions of squirrels for the the return trip north.
Visit the webpage that includes info, photos, and video of this oldest tree.
The International Union for the Conservation of Nature (IUCN) monitors endangered species via its IUCN Red List of Threatened Species. An update of its "critically endangered" Torreya taxifolia IUCN listing in 2011 includes these entries:The estimated 98% decline in mature individuals within the last three generations means that Torreya taxifolia meets the criteria for Critically Endangered under Criterion A2. The actual causes of the decline (the death of individuals and the reproductive failure associated with infection from a range of pathogens) is not well understood: recent surveys indicate it is continuing. The decline may be reversible in the future if those causes can be identified and controlled.
Restricted to a few ravines along the east side of the Appalachicola River in northern Florida and southern Georgia. Its total extent of occurrence is estimated to be about 200 km2 with an area of occupancy under 50 km2.
The current population is estimated to be between 500 and 600 trees. Of these, less than 10 are known to produce male or female cones (this species is dioecious). Individuals persist as stump sprouts. Before the start of the decline in the early 1950s, the population was estimated to have been more than 600,000. Since then there has been a decline of more than 98%.
Torreya taxifolia occurs along limestone bluffs on the Appalachicola River in a region with a warm and humid climate, occasionally influenced in winter by cold waves from the north that dip temperatures below the freezing point. It grows mostly in the shade of wooded ravines and steep, N-facing slopes under canopy of Fagus grandifolia, Liriodendron tulipifera, Acer barbatum, Liquidambar styraciflua, Quercus alba, and occasionally pines (Pinus taeda, P. glabra). Often these woods are hung with vines (e.g. Smilax spp., Bignonia capreolata). Another rare conifer, Taxus floridana, occasionally grows with Torreya taxifolia.
The most significant current threat to T. taxifolia is the continued reproductive failure associated with fungal pathogens. Individuals do not reach reproductive size before being top-killed. Recent research has identified a previously unknown species of Fusarium that may be the cause (J.A. Smith pers. comm. September 2010). Rubbing by deer is an additional problem as it causes physical damage and may also be a vector for disease transmission. Changes in landuse and fire regimes in surrounding areas along with changes in hydrology and soil chemistry linked to the construction of dams may also be implicated in its historical decline. Augmentation plantings within the natural range have proved to be susceptible to infection: no naturally resistant clones have been identified to date. Population viability analyses indicate that extinction within its native range is inevitable. Below: Sample graphic from the IUCN Red List page for Florida Torreya.
Image left from:
Taxonomy and Ecology of Woody Plants in North American Forests:
(Excluding Mexico and Subtropical Florida)
by James S. Fralish and Scott B. Franklin (Feb 8, 2002)
Hardcover: 624 pages
Publisher: Wiley; 1 edition (February 8, 2002)
Note the first sentence:
"Prior to glaciation and the accompanying colder climate, Torreya was circumpolar at high latitudes."
Notice the species richness centered over the Apalachicola region of northern Florida.
Illustration from "Contemporary richness of holarctic trees and the historical pattern of glacial retreat," by Daniel Montoya et al., 2007, Ecography 30:173-182.
• "The Decline of Florida Torreya: An Endemic Conifer on the Edge of Extinction", by Jason A. Smith and Aaron Trulock, 2010, University of Florida School of Forest Resources and Conservation, research paper.
Recent Papers on Stem Canker Pathology (chronological)EXCERPTS: Considered a common tree in its restricted habitat until just before WWII, by 1962 Florida torreya had declined so severely that the species was considered to be destined for extinction (Godfrey and Kurz, 1962). The decline of Florida torreya was first observed around 1938 (Alfieri et al., 1967). By the 1960s, no adult individuals could be found and the outlook for the species seemed very bleak (Alfieri et al., 1967). The rapid decline of the species was then attributed to an unknown fungal disease because of the abundance of leaf spots and stem cankers and the rapid nature of the decline (Godfrey and Kurz, 1962). Since then, Florida torreya has continued to decline and in addition to disease, has been subjected to changes in hydrology, forest structure, heavy browsing by deer and a loss of reproductive capability (Schwartz and Hermann, 1995). Despite these challenges, Florida torreya stems which have been killed by disease often re-sprout from the stump in a manner reminiscent of American chestnut following chestnut blight, although seed reproduction has been non-existent for decades in the wild (Schwartz and Hermann, 1999). Estimates show Florida torreya has declined 99% since pre-settlement population levels, from an estimated population of 357,500 individuals in 1914 to approximately 1,350 in the 1990s (Schwartz et al., 2000). It is believed that the population has declined further since 2000 to current estimates of 400–600 individuals (T. Spector, unpublished data, 2010).• "A Novel Fusarium Species Causes a Canker Disease of the Critically Endangered Conifer, Torreya taxifolia", by Jason A. Smith et al., Plant Disease, June 2011, 7 pp. with photos.
Despite several attempts to conclusively determine the causal agent responsible, disease etiology has not been previously elucidated (Alfieri et al., 1967; Alfieri et al., 1987; El-Gholl, 1985; Lee et al., 1995; and Schwartz et al., 1996). In the first pathology studies conducted on T. taxifolia (Alfieri et al., 1967), it was noted that disease symptoms of leaf spots, needle necrosis, defoliation and stem lesions were common on native and cultivated T. taxifolia. Several pathogens were isolated commonly from symptomatic needles (Macrophoma sp., Rhizoctonia solani, Sphaeropsis sp. and Sclerotium rolfsii), however, no pathogens were isolated from cankered stems and Koch's postulates (proof of pathogenicity) were not demonstrated. About 20 years later, El-Gholl (1985) implicated Fusarium lateritium as a causal agent by demonstrating this species' capacity to cause leaf spots, however, the causal agent of the canker disease remained unknown. Alfieri et al. (1987) completed more pathogenicity studies with a Phyllosticta sp., Xylocoremium flabelliforme and F. lateritium. They also completed Koch's postulates with F. lateritium as a leaf spot pathogen, but the canker-causing organism remained elusive. In 1991, Schwartz et al. implicated Pestalotiopsis microspora as the causal agent of the canker disease, having isolated the pathogen from 56 symptomatic plants and completed Koch's postulates on 10 stems. However, no information was given on the canker development, morphology or ability to cause mortality. Typically Pestalotiopsis spp. are considered opportunistic pathogens (Sinclair, 2005). Lee et al. (1995) investigated the endophytic and pathogenic chemical attributes of P. microspora infection and artificial inoculations resulted in stem canker development, however, again no stem mortality was observed.
Subsequent studies by Hermann and Schwartz (1997) implicated a Scytalidium sp. due to frequent isolation from cultivated and naturally occurring Florida torreya. Inoculation attempts led to small lesions on needles, but cankers were not observed.
In addition to biotic causes of decline, researchers have looked into changes in soils, drought, global warming, sunlight exposure and fire regime as possible causes of decline (Schwartz et al., 1995). Some of these environmental changes are thought to have occurred because of the building of the Woodruff Dam along the Apalachicola River in 1957 (Schwartz et al., 1995), and changing land uses in the surrounding areas. However, none of these environmental hypotheses have been demonstrated as a cause of the decline. The rapid nature of the decline during the period of 1938 to 1945 and numerous observations of disease symptoms provides ample evidence that a pathogen, possibly non-native, was involved (Schwartz et al., 1995).ABSTRACT EXCERPT: A canker disease of Florida torreya (Torreya taxifolia) has been implicated in the decline of this critically endangered species in its native range of northern Florida and southeastern Georgia. In surveys of eight Florida torreya sites, cankers were present on all dead trees and 71 to 100% of living trees, suggesting that a fungal pathogen might be the causal agent. To identify the causal agent, nuclear ribosomal internal transcribed spacer region (ITS rDNA) sequences were determined for 115 fungi isolated from cankers on 46 symptomatic trees sampled at three sites in northern Florida. BLASTn searches of the GenBank nucleotide database, using the ITS rDNA sequences as the query, indicated that a novel Fusarium species might be the etiological agent...• "Host Range and Biology of Fusarium torreyae, Causal Agent of Canker Disease of Florida Torreya, by Aaron J. Trulock, 2012, 55 pp., (master of science thesis, University of Florida).
[Final paragraph]: Florida torreya faces numerous challenges to its future survival in its natural habitat. In addition to the canker disease, deer routinely cause damage to stems from antler rubbing. It is unclear whether they are attracted by the tree's aroma or seek out Florida torreya for some other unknown reason. Whether the wounds caused by deer serve as infection courts for pathogens, including the new Fusarium sp. (Fsp-1), is unclear and warrants further study. Additionally, since lesions on the larger plants in IE3 resulted in less stem girdling and no mortality, the host response to infection, particularly under different stress conditions, needs to be investigated. In addition to more research on the biology and management of CDFT, more work is needed to assess the various factors involved in decline of Florida torreya and how the species can be protected from extinction.Note by Torreya Guardians founder Connie Barlow - Although this paper is not peer-reviewed, p. 18 and the final two paragraphs (pp. 46-47) have been used as a reputable source for implicating northward plantings of Florida torreya by Torreya Guardians as dangerous for possibly spreading Fusarium torreyae to two Appalachian native trees: Fraser Fir and Eastern Hemlock. Because this warning is severe, it would be useful for the experiments leading to this conclusion to be published in full in a peer-reviewed journal. The experiment apparently discovered that the Fusarium "grows well and sporulates in the average summer and fall temperatures" of the southern Appalachians, but there is no mention as to whether population dieback occurs in the kinds of severe winter conditions that periodically occur in mountain locations, and there is no mention of actual testing of the Fusarium on the two tree species concluded as vulnerable.
Importantly, this paper was the first published mention that any danger might be associated with translocating Torreya plant materials geographically. A "novel Fusarium" (later named Fusarium torreyae) was first published as the definitive lethal disease the prior year (see the above, 2011, publication). Prior to Torreya Guardians' first reception of seeds from the Biltmore Gardens ca 2005, movement had been routinely conducted by agents associated with the official USF&WS recovery plan, beginning in 1989. No volunteer planter associated with Torreya Guardians has ever taken any material from the native site (Torreya State Park and surrounds) where the canker is rampant; in contrast, Atlanta Botanical Garden agents for many years have shuttled plant materials, tools, and boots directly between the diseased range and facilities in central Georgia. It is unfair to isolate Torreya Guardians as having potentially moved the then-unknown Fusarium, without acknowledging as well the many years in which researchers, experimenters, and even attendees at the 2018 Torreya Symposium in Torreya State Park might have unknowingly served as more direct vectors for northward movement of the Fusarium.
• "Fusarium torreyae sp. nov., a pathogen causing canker disease of Florida torreya (Torreya taxifolia), a critically endangered conifer restricted to northern Florida and southwestern Georgia", by Takayuki Aoki, Jason A. Smith, Lacey L. Mount, David M Geiser, Kerry O'Donnell, 2013, Mycologia.EXCERPTS (in which the Fusarium is named and distinguished from closest Fusarium relatives): During a survey for pathogens of Florida torreya (Torreya taxifolia) in 2009, a novel Fusarium species was isolated from cankers affecting this critically endangered conifer whose current range is restricted to northern Florida and southwestern Georgia. Published multilocus molecular phylogenetic analyses indicated that this pathogen represented a genealogically exclusive, phylogenetically distinct species representing one of the earliest divergences within the Gibberella clade of Fusarium. Furthermore, completion of Koch's postulates established that this novel species was the causal agent of Florida torreya canker disease. Here we formally describe this pathogen as a new species, Fusarium torreyae.• "Two novel Fusarium species that cause canker disease of prickly ash (Zanthoxylum bungeanum) in northern China form a novel clade with Fusarium torreyae", by Zhou Xue, Kerry O'Donnell, Akayuki Aoki, Jason A. Smith, Matthe T. Kasson, Zhi-Min Cao, 2016, Mycologia.
... The available data suggests these three fusaria can be distinguished by host range in that F. torreyae is known only from Florida torreya (Smith et al. 2011), F. lunulosporum has been isolated only from grapefruit (Gerlach and Nirenberg 1982) and wheat (Gert van Coller, A-L Boutigny, A Viljoen pers comm) in South Africa, and F. tucumaniae has been recovered only from soybean in Argentina and Brazil (Aoki et al. 2003, O’Donnell et al. 2010). The identification of F. torreyae as F. lateritium by El-Gholl (El-Gholl 1985) and subsequent confirmation by Paul E. Nelson (D. Geiser pers comm) illustrate the daunting challenge presented by overly broad morphological concepts of fusaria, especially when applied to species that produce only sporodochial conidia. We speculate that the reported needle blight of Florida torreya induced by F. lateritium in a pathogenicity experiment (Alfieri et al. 1987) also can be attributed to F. torreyae; however, no isolate from this study was accessioned so the identity of this pathogen cannot be verified. Other examples of misplaced Fusarium spp. pathogenic to trees are provided by the etiological agent of coffee wilt disease in Africa, F. xylarioides Steyaert, and vascular wilt of pigeon pea (Cajanus cajan (L.) Millsp.) in Africa and Asia caused by F. udum Butler. The latter two species were classified in section Lateritium by Booth (1971), but molecular phylogenetic analyses have clearly established that they are nested within the African clade of the Gibberella fujikuroi species complex (O’Donnell et al. 1998, Geiser et al. 2005, Lepoint et al. 2005)
Note by Torreya Guardians founder Connie Barlow: This publication mentions a half-dozen Fusarium or other canker-causing pathogens that are all, with the exception of the Florida Torreya tree, hosted on plants that are of food value: a spice in China, cultivated grapefruit, wheat, a soybean cultivar in Argentina and Brazil, coffee bushes in Africa, and the pigeon pea that is cultivated in Africa and Asia. This indicates that the majority of documented pathogenic species of genus Fusarium attack plants of commercial value. Might one wonder: How many Fusarium species exist in southeastern North America and sometimes cause cankers on trees and other native plants, but are undiscovered because no researcher has been funded to isolate them? As well, might Fusarium torreyae be found elsewhere in the southeastern USA, but has not been documented because of low virulence in regions where native plants are less stressed by a deteriorating climate?EXCERPTS: Canker disease of prickly ash (Zanthoxylum bungeanum) has caused a decline in the production of this economically important spice in northern China in the past 25 y. To identify the etiological agent, 38 fungal isolates were recovered from symptomatic tissues from trees in five provinces in China. These isolates were identified by conducting BLASTN queries of NCBI GenBank and phylogenetic analyses of DNA sequence data ... Results of these analyses suggested that 30/38 isolates belonged to two novel fusaria most closely related to the Florida torreya (Torreya taxifolia Arn.) pathogen, Fusarium torreyae in Florida and Georgia. These three canker-inducing tree pathogens form a novel clade within Fusarium here designated the F. torreyae species complex (FTOSC).
...Molecular clock estimates place the divergence of the FTOSC in the mid-Eocene , 40 Mya (O’Donnell et al. 2013), but it remains an open question whether this clade first evolved in the Old or New World. Furthermore, it remains to be determined whether F. torreyae is native to North America and restricted to T. taxifolia. Surveys for F. torreyae on Torreya endemic to China are warranted because it is the modern area of diversity of this genus (Li et al. 2001) and because the putative Asian origin of the CDZB pathogens could indicate that the most recent common ancestor of the FTOSC evolved in Asia. EDITOR'S NOTE: A survey to determine whether a Fusarium is present and causes lethal cankers on Florida Torreya's closest cousin, California Torreya (Torreya californica) is surely "warranted" as well.
... Several species of Fusarium are capable of causing cankers on woody plants, and mixed infections frequently occur. For example, a particular FSSC species occasionally was found co-occurring with F. torreyae in cankers on Florida torreya (Torreya taxifolia) (Smith et al. 2011). Although both species could induce cankers, F. torreyae is considered to be the primary pathogen due to increased virulence and consistent isolation from a large number of cankers. By contrast the available data indicates the FSSC taxon should be regarded as an opportunistic ( J. Smith pers comm).
• "Root and Soil-borne Oomycetes (Heterokontophyta) and Fungi Associated with the Endangered Conifer, Torreya taxifolia in Georgia and Florida, by Lydia I. Rivera Vargas and Vivian Negron-Ortiz, 2013, chapter in book (25 pp).
Elizabeth A. Atchley in 2004 wrote her master's thesis (114 text pages plus references and appendices) on this topic: "The Effects of Habitat Alterations on Growth and Vitality of Torreya taxifolia Arnott in Northern Florida, U.S.A". It is an excellent background document, and can be accessed online in PDF. Key excerpts,Page 2: "Some of the fungi possibly responsible for the blight are common natives that have never been serious problems in the past. There is now much speculation about multiple factors within the environment causing the decline of the T. taxifolia population. Several successive drought years that occurred in the mid-1950s were blamed for the initial decline, but this population is believed to have occupied the area since the last glacial period (Toops, 1981). A population established since then is likely to have survived more severe climatic shifts. Just prior to the decline of Torreya, part of the uplands above the Apalachicola bluffs were cleared and planted with slash pine (Nicholson, 1990). It is believed that the clearing of the area may have changed the hydrology of the ravines, or the reduction of canopy cover may have increased ambient temperature as more heat radiated off the unshaded soil. These factors could have weakened the trees to the point that they were more likely to exhibit pathologic symptoms of the fungus (Nicholson, 1990)."
Page 12: "It is also possible that current populations are climatic relicts that once had a more northerly range, but during the last glacial the advancing ice pushed them south where they mixed with the temperate deciduous forest species. It is possible that when the ice retreated, the Torreya did not reoccupy their northern range and could only survive in cool, moist refuges such as evergreen mountain forests, ravines, and some riverbanks. This is believed to be the case for Torreya taxifolia."
ABSTRACT EXCERPTS: Original research by Atchley centered on tree-ring analysis of downed Torreya logs and living pines. Key paragraphs: "A master chronology extending back to 1869 was established using 125 pine cores. Twenty of the T. taxifolia cross sections were successfully dated, extending the chronology back to 1814. I found a significant positive relationship between growth and spring precipitation and an inverse relationship between growth and summer drought severity and summer temperature. The climate-growth response of T. taxifolia mirrored that of the pines, but was not as intense, possibly because of the protected understory habitat.
"The correlation between tree growth and precipitation suggests that moisture is the strongest determining factor of growth in this area. The inverse relationship with temperature illustrates the effect of higher temperatures on available moisture. A drought and warm period occurred simultaneously during the mid-1950s in combination with heightened clear-cutting practices and the construction of Woodruff Dam. It is my conclusion that habitat destruction occurring as early as the turn of the 20th century began weakening the Torreya. The unfavorable climate conditions and rapid degradation of the habitat that occurred during the mid-1950s further weakened the Torreya and allowed them to succumb to terminal infection by the blight."
Torreya expert Mark Schwartz observes:"There are probably fewer than 1000 individuals extant in the current distribution and the numbers are dwindling. At last count, there is a single known individual that is producing seeds in the wild (personal observation). Aside from this one individual and the approximately 8 seeds it has produced, there has been no observed seedling recruitment for at least 20, and probably 40 years."
See also: "Population Persistence in Florida Torreya: Comparing Modeled Projections of a Declining Coniferous Tree", by Mark W. Schwartz, Sharon M. Hermann, and Phillip J. Van Mantgem, Conservation Biology, 4 August 2000, and "The Population Biology of Torreya taxifolia: Habitat Evaluation, Fire Ecology, and Genetic Variability", by Mark W. Schwartz and Sharon M. Hermann, 1992, Center for Biodiversity Technical Report.
In June 2009, a paper published in the Proceedings of the National Academy of Sciences contained supplementary information that detailed the plight of Florida Torreya. Richardson et al. 10.1073/pnas.0902327106 wrote:
Torreya taxifolia (Cephalotaxaceae) is a dioecious coniferous tree that is endemic to the bluffs that extend 5 to 10 km eastward from the Apalachicola River for approximately 35 km in northern Florida, extending less than a kilometer into Georgia. During the late 1950s and early 1960s, all adult trees throughout its range were killed as a consequence of a pathogen outbreak. The current population is likely not 1,500 individuals, likely seeds and seedlings that were viable at the time of the decline. During the past 40 years, there has been a single tree that has been observed to have matured into a seed-bearing adult. It produced 2 seeds. This individual is now dead, and the seeds produced are presumed dead as well. The agent of the decline is unknown but is thought to be a fungal pathogen. The current rate of decline is slow. Estimates of growth and mortality data suggest that it will be at least a century before the population goes extinct in the wild. Cuttings from 150 trees are currently grown in botanic gardens.
More recently, 2 efforts have begun for the conservation of this species. Torreya taxifolia has been planted in North Carolina in an attempt to establish populations in that region (http:// www.torreyaguardians.org/). This effort was done as an indirect response to climate change. The species is in declining in its native range with no sign of recovery. Proponents felt that this species 'belongs' in the region where they relocated it. They also feel that this intervention is the best chance for the species to survive, given its condition in its native range.
Photos of Diseased Specimens • January 2004
by Connie Barlow • Torreya State Park
SPECIMEN #1. Steve Urse of Tallahassee with a reclining Torreya stem in an upland area near the ravines.
Below: Close-up of the lower stem, with healthy basal sprout on one side and a cluster of basals on the other, cropped by herbivory.
BELOW: Base of Specimen #1 in Florida on the LEFT, compared at RIGHT to an herbivore-damaged young stem in California, next to its healthy mature stem (photo 2005 by Connie Barlow).
SPECIMEN #2 (January 2004)
Multi-stem regrowth Torreya near bridge over creek. Nearby large-stemmed trees include Bald Cypress, American Holly, American Beech, Southern Magnolia. The five remaining photos show close-ups of diseased areas of stems and leaves.
OTHER PHOTOS OF TORREYA IN TORREYA STATE PARK
Access a webpage for a PHOTO-ESSAY BY GLENN RILKE of his periodic visits to surviving Torreya trees in historically native range in Torreya State Park (panhandle of Florida).
Note by Connie Barlow: Two early contributors to professional field studies of Torreya taxifolia, Mark Schwartz and Sharon Hermann, published in 1999 a paper on their study of Torreya californica in the field: "Is Slow Growth of the Endangered Torreya taxifolia (Arn.) Normal?", Journal of the Torrey Botanical Society. Their final paragraph:In aggregate, the results of this work suggest that the observed low growth rates of T. taxifolia might not be indicative of disease-induced stress. The similarity between T. taxifolia and T. californica growth rates and patterns is consistent with the hypothesis that T. taxifolia is growing normally within its environment. The infrequent expansion of terminal buds may simply be the way that these trees naturally grow in low light environments. Evidence of suppression and release growth pattern in tree rings, along with a preliminary observation that trees in high light environments grow more frequently than those in low light, support the hypothesis that growth in T. taxifolia is light limited. Given the continued lack of an identified primary disease agent, we recommend pursuing further tests of the light limitation hypothesis, and management to increase light levels above extant trees in the wild.Barlow adds: This is a helpful paper. My own natural history observations in 2005 (at a greater number and diversity of sites than the quantitatively driven experimental approach undertaken by Schwartz and Hermann) would add two interpretations: (1) Genus Torreya evolved as a definitive sub-canopy species (as are other members of the yew family); presumably with the assistance of mycorrhizae it is capable of living a very long time in a seemingly stunted state, until a canopy opening enables growth and also seed production on the individual branches that can access sufficient sunlight. (2) With the rare exception of the immense Torreya trees found along Swanton Creek north of Santa Cruz (which is artificial, given that the canopy redwoods were removed in the early 20th century, thus artificially releasing a population of subcanopy Torreyas to grow tall and to seed), Torreya seems to do best on extremely steep slopes, where the usual canopy giants (Coast Redwoods and Douglas-fir) are not found.
Access my PHOTO-ESSAYS OF CALIFORNIA TORREYA GROVES or my 2-part NARRATED VIDEO OF TORREYA CALIFORNICA.
"Coevolution of Cycads and Dinosaurs" paper by George E. Mustoe, The Cycad newsletter, March 2007.Barlow and Martin 2004 proposed that Torreya taxifolia might have gotten trapped in its peak-glacial pocket reserve (in northern Florida) for lack of its coevolved seed disperser, and thus was unable to geographically respond to the warming interglacial climate. The above paper suggests that another taxon of gymnosperm that thrived (along with genus Torreya) in the Jurassic period might have suffered from an inability to easily track climate change when the seed-dispersing dinosaurs died out.
Access in PDF two articles, for and against assisted
migration of Torreya taxifolia, published as the featured
Forum in the Winter 2005 issue of Wild Earth. Download
the pro and con articles separately for printing on standard
size paper. Or, for viewing the 2-article Forum as it
appeared in publication (wide-screen, with all illustrations),
download the "Forum."
FOR assisted migration, by Connie Barlow & Paul Martin
ANTI assisted migration by Mark Schwartz
FORUM (both articles for wide screen)
Standards for Assisted Migration (by Barlow & Martin 2004)
"Rewilding North America" The 18 August 2005 issue
of the prestigious science journal, Nature contains an advocacy
article that proposes "rewilding" close-kin of some of the
large mammals that went extinct in North America at the
end of the Pleistocene, 13 thousand years ago. By comparison,
the proposal to "Rewilding Torreya taxifolia" looks mild! To access
this amazing article, you can view or download it at
The Apalachicola as a Peak-Glacial Habitat
Palynologist Hazel Delcourt, botanist Rob Nicholson, and others have each independently concluded that the Apalachicola habitat in which T. tax is found is one of a small group of "pocket refuges" along the Gulf (and southern Atlantic) coasts in which the vast majority of warm and cool temperate plant species found crucial refuge when the Pleistocene continental glaciers achieved their peak advances during the past 2 million years. Without these refuges, it is likely that North America would have lost not only Torreya taxifolia but also its tuliptrees, sweet gum trees, bald cypress, hemlocks, and a host of shrubs and forbs (such as mayapple). How do we know this? Because Europe lost these species, presumably owing to unfortunate geography: southward migration blocked by the Mediterranean, Black Sea, Carpathian Mountains, etc.
ABOVE left: Tuliptree. ABOVE right: Sweetgum
BELOW left: Bald cypress (Taxodium) BELOW right: Franklinia
Indeed, the species name of Franklinia, Franklinia alatamaha derives from the only place this lovely tree was found the Altamaha River of southeastern Georgia before it vanished from the wild. The Altamaha River thus joins the Apalachicola (and the Tunica Hills of Louisiana) as a peak-glacial pocket refuge for plants of eastern North America.
ABOVE: Two of the three crucial peak-glacial pocket refuges include the Apalachicola River of the Florida panhandle and the lower reaches of the Altamaha River of southeastern Georgia (both shown in yellow; orange denotes the section of the Apalachicola containing T. tax).
"A Remarkable Colony of Northern Plants Along the Apalachicola River, Florida, and Its Significance"KEY SECTION:
by H. C. Cowles, 1905
Report of the Eighth International Geographic Congress
Held in the United States
"In this association one finds two of our most notable endemic plants Torreya and Croomia. It seems likely, then that we should regard Torreya taxifolia as a northern mesophytic left stranded to-day only in Florida.
"It presumably is one of the plants that failed to follow up the last retreat of the Pleistocene ice, and is preserved here perhaps because of exceptionally favorable topographic conditions."
Where Should "Native" Range Be During an Interglacial?
If the Apalachicola is, in fact, peak-glacial habitat for Torreya taxifolia, then we might conjecture that, for some reason, Torreya taxifolia (as well as the equally endemic, though not equally stressed, Florida yew) was unable to migrate north in tandem with a warming climate during the past 15,000 years. Thus where might its "native" range be at this point in an interglacial?
Learn about efforts to SAVE Torreya taxifolia from extinction and how our actions are legal. Explore a photo-essay of Torreya Guardians REWILDING ACTION in North Carolina (2008).