Taccachantrieri
Well-Known Member
After hearing about San Diego Zoos plans for this exhibit I was somewhat reminded of “Pleistocene rewilding†proposed by Donlan, C. Josh; Berger, Joel; Bock, Carl E., et al. (2006).
These authors argue that Pleistocene North America was inhabited by a diverse group of large mega fauna terrestrial vertebrates that were driven to extinction by humans, and that we should consider restoring ecosystem balance by establishing extant conspecifics and related taxa in these areas. Basically this would involve establishing wild populations of the animals featured in San Diego Zoos Elephant Odyssey in the southwestern United States.
The authors further advocate for thorough scientific investigations and
evaluations, as well as cost benefit calculations for each individual species in each area to determine the conservation value of establishing these populations.
By thirteen thousand years ago North America had lost most of its large mammals which is roughly coincident with the arrival of humans in North America and may have been caused by them. C. Josh Donlan, et al believes that these extinctions caused a precipitous top down effect on ecological and evolutionary changes and still exert detrimental effects on present biodiversity.
Ecological arguments used are very similar to those encountered on these forums (that are actually used on these forums as counters to some of my arguments). They argue that large megafauna have a disproportionate influence on ecosystem function and that their extinction has led to numerous other extinctions that will further decrease biodiversity.
Maclura, a large fruited plant, was widely distributed and more diverse in Pleistocene North America. Large Proboscideans and other large herbivores extinctions may have led to the decline of Maclura as they were likely agents of dispersion.
The extraordinary speed of pronghorns of up to 60 mph is likely an adaptation to evade North American “cheetahsâ€Â. The full phenotypic expression of this feature is often suppressed in modern environments, but could be restored by introducing cheetahs into North America.
One interesting link drawn in this study is that between wolf extirpation and Lyme disease. The loss of this predator in many areas of North America has led to increases in abundance of deer and other large ungulates especially in normally avoided wooded areas. Recently there have been several outbreaks amongst humans in North America of Lyme disease in areas where wolves have been extirpated.
Large mammals are becoming extinct across the world. North American populations could act as refugia in case populations in native countries became extirpated.
Pleistocene rewilding could also have numerous economic benefits including reinvigoration of park revenue and tourism.
However, I can mount numerous objections to this approach in conservation.
To begin with a lot of the North American Pleistocene mammals are quite different from their extant exotic relatives. Asian elephants may be more closely related to North American mammoths than African elephants, but they are still two different genera that diverged millions of years ago. North American cheetahs may be convergent to African forms and have arisen from a common ancestor shared with pumas. There are even differences between North American and modern lions, thought to be the same species. The former may not have had manes and had an estimated weight more than twice that of modern lions! This is to say nothing of the different ecological roles and functions exerted by the two types of lions.
No amount of research is ever going to reveal every difference between North American Pleistocene mammals and extant exotic species so it is exceedingly difficult to predict every possible ecological ramification and disruption so risks remain high despite scientific investigations.
Furthermore, North American populations have had thousands of years to adapt to the absence of large megafauna and reintroducing them could disrupt current balances.
Contrary to the authors supposed negative ecological ramifications of North America megafauna extinctions, diversity of small animals and plants has remained relatively constant from the Pleistocene to the present day, which is even stated near the end of their paper! Where is the ecological collapse they envisioned?
Disease transmission is a huge concern even for individuals being released back into areas historically or currently inhabited by that species. Imagine the difficulties that could arise in introducing animals from different continents potentially introducing diseases that have never been in North America!
Introductions of any kind can be excessively expensive. These costs would probably be even higher if exotic species were to be introduced into North America because of their lower success rate from evolving to quite different ecological and environmental conditions. Elephants and lions would require modifications to park structures like overpasses, fencing, etc. that would incur further costs. Loss of park revenue in the United States cannot be explained solely by loss of large interesting species and probably has numerous causes that could be solved by means other than introducing exotic megafauna.
I think one of the biggest problems with Pleistocene rewilding is the messages it can send the public. Instead of seeing extinctions as a process that irrevocably damages ecosystems and removes biodiversity this conservation approach may suggest that extinctions can be reversed and that could make the public feel less pressured to act immediately on the global extinction crisis.
C. Josh Donlan, Joel Berger, Carl E. Bock, Jane H. Bock, David A. Burney, James A. Estes, Dave Foreman, Paul S. Martin, Gary W. Roemer, Felisa A. Smith, Michael E. Soule´, and Harry W. Greene. 2006. Pleistocene rewilding: An optimistic agenda for twenty-first century conservation. American Naturalist Volume 168 (5): 660-681
These authors argue that Pleistocene North America was inhabited by a diverse group of large mega fauna terrestrial vertebrates that were driven to extinction by humans, and that we should consider restoring ecosystem balance by establishing extant conspecifics and related taxa in these areas. Basically this would involve establishing wild populations of the animals featured in San Diego Zoos Elephant Odyssey in the southwestern United States.
The authors further advocate for thorough scientific investigations and
evaluations, as well as cost benefit calculations for each individual species in each area to determine the conservation value of establishing these populations.
By thirteen thousand years ago North America had lost most of its large mammals which is roughly coincident with the arrival of humans in North America and may have been caused by them. C. Josh Donlan, et al believes that these extinctions caused a precipitous top down effect on ecological and evolutionary changes and still exert detrimental effects on present biodiversity.
Ecological arguments used are very similar to those encountered on these forums (that are actually used on these forums as counters to some of my arguments). They argue that large megafauna have a disproportionate influence on ecosystem function and that their extinction has led to numerous other extinctions that will further decrease biodiversity.
Maclura, a large fruited plant, was widely distributed and more diverse in Pleistocene North America. Large Proboscideans and other large herbivores extinctions may have led to the decline of Maclura as they were likely agents of dispersion.
The extraordinary speed of pronghorns of up to 60 mph is likely an adaptation to evade North American “cheetahsâ€Â. The full phenotypic expression of this feature is often suppressed in modern environments, but could be restored by introducing cheetahs into North America.
One interesting link drawn in this study is that between wolf extirpation and Lyme disease. The loss of this predator in many areas of North America has led to increases in abundance of deer and other large ungulates especially in normally avoided wooded areas. Recently there have been several outbreaks amongst humans in North America of Lyme disease in areas where wolves have been extirpated.
Large mammals are becoming extinct across the world. North American populations could act as refugia in case populations in native countries became extirpated.
Pleistocene rewilding could also have numerous economic benefits including reinvigoration of park revenue and tourism.
However, I can mount numerous objections to this approach in conservation.
To begin with a lot of the North American Pleistocene mammals are quite different from their extant exotic relatives. Asian elephants may be more closely related to North American mammoths than African elephants, but they are still two different genera that diverged millions of years ago. North American cheetahs may be convergent to African forms and have arisen from a common ancestor shared with pumas. There are even differences between North American and modern lions, thought to be the same species. The former may not have had manes and had an estimated weight more than twice that of modern lions! This is to say nothing of the different ecological roles and functions exerted by the two types of lions.
No amount of research is ever going to reveal every difference between North American Pleistocene mammals and extant exotic species so it is exceedingly difficult to predict every possible ecological ramification and disruption so risks remain high despite scientific investigations.
Furthermore, North American populations have had thousands of years to adapt to the absence of large megafauna and reintroducing them could disrupt current balances.
Contrary to the authors supposed negative ecological ramifications of North America megafauna extinctions, diversity of small animals and plants has remained relatively constant from the Pleistocene to the present day, which is even stated near the end of their paper! Where is the ecological collapse they envisioned?
Disease transmission is a huge concern even for individuals being released back into areas historically or currently inhabited by that species. Imagine the difficulties that could arise in introducing animals from different continents potentially introducing diseases that have never been in North America!
Introductions of any kind can be excessively expensive. These costs would probably be even higher if exotic species were to be introduced into North America because of their lower success rate from evolving to quite different ecological and environmental conditions. Elephants and lions would require modifications to park structures like overpasses, fencing, etc. that would incur further costs. Loss of park revenue in the United States cannot be explained solely by loss of large interesting species and probably has numerous causes that could be solved by means other than introducing exotic megafauna.
I think one of the biggest problems with Pleistocene rewilding is the messages it can send the public. Instead of seeing extinctions as a process that irrevocably damages ecosystems and removes biodiversity this conservation approach may suggest that extinctions can be reversed and that could make the public feel less pressured to act immediately on the global extinction crisis.
C. Josh Donlan, Joel Berger, Carl E. Bock, Jane H. Bock, David A. Burney, James A. Estes, Dave Foreman, Paul S. Martin, Gary W. Roemer, Felisa A. Smith, Michael E. Soule´, and Harry W. Greene. 2006. Pleistocene rewilding: An optimistic agenda for twenty-first century conservation. American Naturalist Volume 168 (5): 660-681
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