Pleistocene rewilding

See also: Rewilding Institute

Near the end of the Pleistocene, roughly 13,000 to 10,000 years ago, nearly all megafauna in South, Central and North America had gone extinct. With the loss of megaherbivores and megapredators, niches important for ecosystem functioning were left unoccupied (Jazen and Martin 1982). Paul Martin (2005), the founder 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 flora and fauna evolved under the influence of large mammals. Based on this premise, Pleistocene Rewilding promotes the reintroduction of descendants of Pleistocene megafauna and/or the closest extant ecological equivalents for those large mammals that went extinct during the Pleistocene. This proposal assumes that communities today are ecologically similar to communities in the Pleistocene and thus that introducing megafauna that are functionally similar to those that went extinct 13,000 years ago would promote biodiversity. Pleistocene rewilding is an extension of the conservation practice rewilding which involves reintroducing species to areas they went extinct from in recent history (hundreds of years ago) (Rubenstein et al. 2006). The fact that Pleistocene rewilding is based on ecosystems that evolved 13,000 years ago makes it very different from and much more controversial than rewilding.

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 (Galetti 2004, Donlan et al. 2006). This idea is supported by the significant impacts that extant megafauna have on the communities they occupy. Today most megafauna are threatened or endangered. If implemented, Pleistocene rewilding could “serve as additional refugia to help preserve that evolutionary potential”of megafauna (Galetti 2004, Donlan et al. 2006). Therefore, reintroducing megafauna to North America could preserve today’s megafauna while filling ecological niches that have been vacant since the Pleistocene (Donatti et al. 2007).

Prospective Taxa for Reintroduction

The Pleistocene rewilding has considered the reintroduction of the Bolson Tortoise, the feral horse, camelids, the Asian elephant, the Old World cheetah and lions. The Bolson tortoise, which nearly went extinct during the Pleistocene, constructs burrows that are thought to increase biodiversity by creating heterogeneity in the environment. Bolson tortoise reintroduction is already underway (Donlan et al. 2006). 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 (Fahnestock & Delting 1999). Camelids evolved in North America and can increase biodiversity by browsing on plants that out-compete desert scrub and grassland species (Donlan et al. 2006). Camelids have been introduced in some areas of North America. Asian elephants play a similar functional role to 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 (Koppel 1998). Because elephants lack major predators (besides humans) and can have such a profound effect on community structure, they are comparable in function to top predators in top-down regulation (Terborgh 1999). The North American cheetah went extinct at the end of the Pleistocene. The Old World cheetah, alive today, is related to the North American cheetah, making it a good candidate for the Pleistocene rewilding. Pronghorn antelope evolved remarkable speed and visual acuity due to selective pressures from the North American cheetah and thus today lack their key predator in North America. Extant lions play a key role in prey regulation which no doubt have indirect effects on community structure (Donlan et al. 2006). All of the above megafauna, with the exception of camelids, are facing the threat of extinction, making megafauna conservation an immediate concern.

The Pleistocene parks idea was first suggested for Arctic (Zimov 2005) and South American ecosystems (Galetti 2004) but less publicized. Galetti (1994) 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 (Donatti et al. 2007, Guimarães Jr. et al. 2008). 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 and camelids has already begun. To date, there is no active plan to reintroduce megafauna such as elephants, cheetahs and lions due to the controversial nature of these reintroductions.

The southwestern United States is the most likely part of North America and in Brazilian savannas where the Pleistocene rewilding could be implemented. Besides fencing the land tracts, a natural setting would be maintained in which predator and prey dynamics would be allowed; the goal of these protected areas would be to achieve ecosystem functioning with megafauna intact (Galetti 2004). The vision for the long term would be to have an “ecological history park encompassing thousands of square miles in economically depressed parts of the Great Plains” (Donlan et al. 2006).

Animals most likely to be chosen for the park project: Przewalski's horse, Dromedary, American Black bear, Grizzly bear, Cheetah, Grey wolf, Guanaco and/or Vicuña, Asian elephant, Mountain tapir and/or Baird's tapir, Muskox , Onager, Saiga antelope, Jaguar, Cougar, Coyote, Collared Peccary, Siberian Tiger, Barbary Lion, and American Bison

Criticism

The main criticism of the Pleistocene rewilding is that it is unrealistic to assume that communities today are functionally similar to how they were 13,000 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, etc. (Rubenstein et al. 2006). Opponents of the Pleistocene rewilding present an alternative conservation effort in which North American natives will be reintroduced into parts of their ranges where they went extinct in more recent history (Rubenstein et al. 2006).

References

• Galetti, M. 2004. Parks of the Pleistocene: recreating the cerrado and the Pantanal with megafauna. Natureza e Conservação 2(1): 93-100.

• Donlan, C.J., J. Berger, C.E. Bock, J.H. Bock, D.A. Burney, J.A. Estes, D. Foreman, P.S. Martin, G.W. Roemer, F.A. Smith, M.E. Soule and H. W. Greene. 2006. Pleistocene Rewilding: An Optimistic Agenda for Twenty-First Century Conservation. The American Naturalist 168: 1-22.

• Fahnestock, J. T. and J.K. Delting. 1999. The influence of herbivory on plant cover and species composition in the Pryor Mountain Wild Horse Range, USA. Plant Ecology 144: 145-157.

• Koppel, J. V. D. and H.H.T. Prinst. 1998. The importance of herbivore interactions for the dynamics of African savanna woodlands: an hypothesis. Journal of Tropical Ecology 14: 565-576.

• Martin, P. S. Twilight of the Mammoth: Ice Age Extinction and the Rewilding of America. Berkley: University of California Press, 2005.

• Rubenstien, D.R., D.I. Rubenstein, P.W. Sherman, T.A. Gavin. 2006. Pleistocene Park: Does re-wilding North America represent sound conservation for the 21st century?

• Terborgh, J., J.A. Estes, P. Paquet, K. Ralls, D. Boyde-Heger, B.J. Miller and R.F. Joss. 1999. The role of top carnivores in regulating terrestrial ecosystems. In Continental conservation: scientific foundations of regional reserve networks. Washington, D.C.: Island Press, 1999.

• Guimarães Jr, P., Galetti, M. and Jordano, P. 2008. Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate. PLoS ONE, (In Press)

• Donatti, C.I., Galetti, M., Pizo, M.A., Guimarães Jr., P.R., and Jordano, P. 2007. Living in the land of ghosts: Fruit traits and the importance of large mammals as seed dispersers in the Pantanal, Brazil. Pages 104-123 in: Dennis, A., Green, R., Schupp, E.W., and Wescott, D. (eds.). Frugivory and seed dispersal: theory and applications in a changing world. Commonwealth Agricultural Bureau International, Wallingford, UK.

External links

• Mauro Galetti
• Paulo Guimarães Jr.
• Pedro Jordano
• The Rewilding Institute
• C. Josh Donlan
• Re-wilding North America
• Where the Wild Things Were
• Rewilding Megafauna: Lions and Camels in North America?
• Pleistocene Park Could Solve Mystery of Mammoth's Extinction

Gallery

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