"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.
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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.
You can access in PDF the official USFWS plan (updated summer 2010) for managing this endangered species.
LEFT: The Apalachicola River in Florida's Torreya State Park (January)
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Elizabeth A. Atchley in 2004 wrote her master's thesis 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. Page 12 includes,
"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.
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."
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 5Ð10 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.
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| Specimen No. 1 Reclining Specimen #1 at Torreya State Park
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| Bark damage near base of Specimen No. 1. (Notice browsed suckers to right.) |
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| Specimen No. 2
Specimen #2 near creek (with bald cypress knees visible), amid American holly tree, beech, evergreen magnolia), January. |
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Evidence of pathogens on foliage (left) and stem (right) on Specimen No. 2 |
"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.
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Download 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."
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FOR assisted migration, by Connie Barlow & Paul Martin
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ANTI assisted migration by Mark Schwartz
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FORUM (both articles for wide screen)
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"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
http://rewilding.org/pdf/Pleistocene-Re-wildingNorthAmerica1.pdf.
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Learn about efforts to SAVE Torreya taxifolia from extinction.
Explore a photo-essay of Torreya Guardians REWILDING ACTION in Waynesville, NC in July 2008.
Return to HOME PAGE.
Annotated List of Papers/Reports Online re Assisted Migration
Who Are Torreya Guardians?
Who Is Torreya taxifolia?
Brink of Extinction
Efforts to Save
Rewilding Now!
Comments on Rewilding
Recruiting Landowners & Helpers
Torreya Plantings in North Carolina
California's Torreya
Propagation Advice
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