Pleistocene Rewilding

Pleistocene Rewilding promotes the reintroduction of descendants of Pleistocene megafauna, or their close ecological equivalents. Toward the end of the Pleistocene era, between roughly 13,000 to 10,000 years ago, nearly all megafauna of South, Central, North America and Europe had dwindled toward extinction. With the loss of the large herbivores and predator species, niches important for ecosystem functioning were left unoccupied. cite journal|title=Neotropical Anachronisms: The Fruits the Gomphotheres Ate |journal=Science|date=1982-01-01|first=Daniel H.|last=Janzen|coauthors=Paul S. Martin|volume=215|issue=4528|pages=19-27|id= doi|DOI: 10.1126/science.215.4528.19|url=http://www.sciencemag.org/cgi/reprint/215/4528/19.pdf|format=PDF|accessdate=2008-07-29 ] Paul Martin, the originator of the Pleistocene rewilding idea, claims that present ecological communities in North America do not function appropriately in the absence of megafauna because much of the native flora and fauna evolved under the influence of large mammals. cite book | last =Martin | first =Paul S. | title =Twilight of the Mammoth: Ice Age Extinction and the Rewilding of America | publisher =UC Press | date = | location =Berkeley | url =http://www.amazon.com/Twilight-Mammoths-Extinctions-Rewilding-Environments/dp/0520252438/ref=sr_1_1?ie=UTF8&s=books&qid=1217286333&sr=8-1 | isbn =0520252438 ] Pleistocene rewilding is an extension of the conservation practice of "rewilding," which involves reintroducing species to areas where they became extinct in recent history (hundreds of years ago, or even less).cite web | last =Rubenstein | first =D.R. | coauthors =D.I. Rubenstein, P.W. Sherman, T.A. Gavin | title =Pleistocene Park: Does re-wilding North America represent sound conservation for the 21st century? | date =2006 | url =http://www.eeb.princeton.edu/FACULTY/Rubenstein/pdf/RubensteinDR&DI_BioCons_2006.pdf | format =PDF | accessdate =2008-07-28 ] The fact that Pleistocene rewilding is based upon the dynamics of ecosystems many thousands of years ago lends it a grander breadth, but also makes it much more controversial than rewilding as presently practiced.

Ecological and Evolutionary Implications

Research shows that species interactions play a pivotal role in conservation efforts. Thus communities where species evolved in response to Pleistocene megafauna but now lack large mammals could be in danger of collapse.cite journal | last =Galetti | first =M. | title =Parks of the Pleistocene: Recreating the cerrado and the Pantanal with megafauna | journal =Natureza e Conservação | volume =2 | issue =1 | pages =93-100 | date =2004 ] cite journal | last =Donlan | first =C.J. | coauthors =et al | title =Pleistocene Rewilding: An Optimistic Agenda for Twenty-First Century Conservation | journal =The American Naturalist | volume = | pages =1-22 | date =2006 | url =http://www.eeb.cornell.edu/donlan/PDFS/donlan_etal_2006.pdf | ] This idea is supported by the significant impacts that extant megafauna have on the communities they occupy (given that most living megafauna are threatened or endangered). If implemented, Pleistocene rewilding could “serve as additional refugia to help preserve that evolutionary potential” of megafauna. Therefore, reintroducing megafauna to North America could preserve today’s megafauna while filling ecological niches that have been vacant since the Pleistocene.Citation| first=C.I. | last=Donatti| coauthors=M. Galetti, M.A. Pizo, P.R. Guimarães Jr., and P. Jordano | contribution=Living in the land of ghosts: Fruit traits and the importance of large mammals as seed dispersers in the Pantanal, Brazil| title=Frugivory and seed dispersal: theory and applications in a changing world| editor-first=A.| editor-last=Dennis| coeditors=R. Green, E.W. Schupp, and D. Wescott| publisher=Commonwealth Agricultural Bureau International| place=Wallingford, U.K.| pages=104-123 | date=| year=2007| id= | contribution-url=| format=| accessdate= ]

Prospective Taxa for Reintroduction

The Pleistocene rewilding has considered the reintroduction of the Bolson Tortoise, the feral horse, camelids, the elephant species, and the Old World cheetah and lions. The Bolson Tortoise, which nearly went extinct during the Pleistocene, constructs burrows that are thought to increase local biodiversity by creating heterogeneity in the environment. Bolson Tortoise reintroduction is already underway. Feral equids have a longstanding history in North America and can be functionally important by dispersing seeds and preventing competitive exclusion. Their restoration is in part underway in places like the Pryor Mountain Wild Horse Range (PMWHR) located in Montana and Wyoming. [ cite journal|title=The influence of herbivory on plant cover and species composition in the Pryor Mountain Wild Horse Range, USA|journal=Plant Ecology|date=1999|first=J. T.|last=Fahnestock|coauthors=J.K. Delting|volume=144|issue=|pages=145-157|id= |url=|format=|accessdate= ] The Camelidae evolved in North America and can increase biodiversity by browsing on plants that out-compete desert scrub and grassland species. Camelids have already been introduced to some arid locations of North America. Elephants play a similar functional role as camelids, but on a much broader scale. They deter the encroachment of woodlands by trampling tree seedlings and foraging on young trees that would otherwise out-compete grassland species for light. These processes maintain grassland community structure, allowing small herbivores that depend on grasslands to persist. cite journal|title=The importance of herbivore interactions for the dynamics of African savanna woodlands: an hypothesis|journal=Journal of Tropical Ecology|date=1998|first=J.V.D.|last=Koppel|coauthors=H.H.T. Prinst|volume=14|issue=|pages=565-576|id= |url=|format=|accessdate= ] Because adult elephants lack major predators besides humans and can have such a profound effect on community structure, they are comparable in function to superpredators in top-down regulation.cite book |last=Terborgh |first=J | coauthors=J.A. Estes, P. Paquet, K. Ralls, D. Boyde-Heger, B.J. Miller and R.F. Joss |title=The role of top carnivores in regulating terrestrial ecosystems |origyear=1999 |series=Continental conservation: scientific foundations of regional reserve networks |year=1999 |publisher=Island Press |location=Washington, D.C. ] The American cheetah went extinct at the end of the Pleistocene. The Old World cheetah alive (but struggling) today, is closely related to the North American cheetah, making it a good candidate for the Pleistocene rewilding. The Pronghorn Antelope, by far the fastest terrestrial creature in North America today, evolved its remarkable speed and visual acuity due to selective pressures such as (quite possibly) the North American cheetah, and thus today lack key predators that can match their great speed. Extant lions -- kin to the now-extinct American Lion, "Panthera leo atrox" -- play a key role in prey regulation on the African savannas, which no doubt also has indirect effects on local community structure. All of the above megafauna are facing the threats of endangerment or extinction, making megafaunal conservation an immediate concern.

The Pleistocene parks idea was first suggested for Arctic and South American ecosystems, but less publicized. cite journal|title=Pleistocene Park: Return of the Mammoth's Ecosystem|journal=Science|date=2005-05-06|first=Sergey A.|last=Zimov|coauthors=|volume=308|issue=5723|pages=796-798|id= doi|DOI: 10.1126/science.1113442|url=http://www.sciencemag.org/cgi/content/full/308/5723/796|format=|accessdate=2008-07-29 ] Mauro Galetti suggested that several plant species in South America lost their major megafauna seed dispersers in the end of the Pleistocene. Secondary seed dispersal, water and indigenous people were responsible for maintaining the seed dispersal process in the last 10,000 years. [ cite journal|title=Seed dispersal anachronisms: Rethinking the fruits extinct megafauna ate|journal=PLoS ONE|date=2008|first=P.|last=Guimarães Jr.|coauthors=M. Galetti and P. Jordano|volume=|issue=In Press|pages=|id= |url=|format=|accessdate= ] Therefore, the rewilding South American savannas will establish a lost seed dispersal services and also control unburned vegetation (due to the lack of megaherbivores). Brazilian savannas burn and release tons of carbon dioxide to the atmosphere yearly. Asian elephants, horses, llamas and other large mammals can be used to control the fires in some cases.

Implementation

The reintroduction of Bolson Tortoise, equids (see Mustang and Burro and camelids (Dromedary) has already begun. Muskoxen roam areas of Europe and Asia last grazed during the heydays of Rome, and bison herds thrive in subarctic Canada and Alaska. To date, however, there are no active plans to reintroduce more exotic megafauna such as elephants, cheetahs or lions due to the controversial nature of these reintroductions.

The Southwestern United States and the Brazilian savanna are the most suitable parts of North and South America where the Pleistocene rewilding could be implemented. Besides fencing off large land tracts, a natural setting would be maintained in which predator and prey dynamics would take their course uninterrupted. The long term plan is for an “ecological history park encompassing thousands of square miles in economically depressed parts of the Great Plains.”

Animals most likely to be chosen for this project might include: Przewalski's horse and Onager (as proxies for e.g. Scott's Horse, Hagerman Horse and the Yukon Wild Horse; Dromedary, Bactrian Camel, Guanaco or Vicuña (in the stead of what was likely a great diversity of camelids, including "Camelops"); Mountain Tapir and Baird's Tapir (formerly part of a widespread Holarctic family); Saiga Antelope (a Pleistocene resident of the Alaskan steppe, now found only in Central Asia); Cheetah; Lion; and African and/or Asian Elephants (the latter being the closest living kin to the genus "Mammuthus").

Criticism

The main criticism of the Pleistocene rewilding is that it is unrealistic to assume that communities today are functionally similar to their state 10,000 years ago. Opponents argue that there has been more than enough time for communities to evolve in the absence of megafauna, and thus the reintroduction of large mammals could thwart ecosystem dynamics and possibly cause collapse. Under this argument, the prospective taxa for reintroduction are considered exotic and could potentially harm natives of North America through invasion, disease, or other factors.

Opponents of the Pleistocene rewilding present an alternative conservation program in which more recent North American natives will be reintroduced into parts of their native ranges where they went extinct in historical times.

References

External links

* [http://www.rc.unesp.br/ib/ecologia/fenologia/prof.html Mauro Galetti]
* [http://www.guimaraes.bio.br/ Paulo Guimarães Jr.]
* [http://ebd10.ebd.csic.es/Home.html Pedro Jordano]
* [http://www.rewilding.org/ The Rewilding Institute]
* [http://www.eeb.cornell.edu/donlan/donlan.html C. Josh Donlan]
* [http://rewilding.org/pdf/Pleistocene-Re-wildingNorthAmerica1.pdf Re-wilding North America]
* [http://www.conbio.org/cip/article71wil.cfm Where the Wild Things Were]
* [http://www.actionbioscience.org/newfrontiers/barlow.html Rewilding Megafauna: Lions and Camels in North America?]
* [http://www.livescience.com/animals/050506_mammoth_park.html Pleistocene Park Could Solve Mystery of Mammoth's Extinction]