Wednesday, May 17, 2006
DID GLOBAL WARMING CAUSE MEGAFAUNA EXTINCTIONS?
A couple of responses to an article with the above title posted on CCnet. The article was about the disappearance of everything from mammoths in Asia to giant everythings in the Americas & giant Moa in New Zealand at a time period which usually roughly coincides with the last Ice Age & very closely coincides with human beings turning up.
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If a major catastrophe kills 90% of a species then to kill 95% would require a doubly great catastrophe & so on. I find it unlikely that, due to the law of diminishing returns reduction to less than 1 breeding group, of a widespread numerous species could be achieved by anything much short of a meteor that produces continent sized sterilisation.
Hunting on the other hand, since it tends to kill at a fairly flat rate, assuming a flat population of hunters & so long as prey is available. This can quite effectively reduce a declining population to zero.
Neil Craig
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(14) DID GLOBAL WARMING CAUSE MEGAFAUNA EXTINCTIONS?
Andre Bijkerk
Dear Benny,
The answer to that question is no. Whilst the temperature changes were indeed gradual, easy to cope with for fauna, the precipitation changes were overnight, and that was the real killer. In Siberia the dry steppes changed in marshed and swamps in the Preboreal, following the Younger Dryas causing the last mammoths to go extinct around 11,200 Cal BP (9600 carbion years), The American megafauna perished at the beginning of the Younger Dryas, around 12500 Cal BP (ca 10500 carbon years) with an extreme dry period.
Our paper regarding this theory is under review of Quartenary International.
Non calor sed umor.
Andre
CCNet is a scholarly electronic network edited by Benny Peiser. To subscribe, send an e-mail to listserver@livjm.ac.uk ("subscribe cambridge-conference").
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If a major catastrophe kills 90% of a species then to kill 95% would require a doubly great catastrophe & so on. I find it unlikely that, due to the law of diminishing returns reduction to less than 1 breeding group, of a widespread numerous species could be achieved by anything much short of a meteor that produces continent sized sterilisation.
Hunting on the other hand, since it tends to kill at a fairly flat rate, assuming a flat population of hunters & so long as prey is available. This can quite effectively reduce a declining population to zero.
Neil Craig
============
(14) DID GLOBAL WARMING CAUSE MEGAFAUNA EXTINCTIONS?
Andre Bijkerk
Dear Benny,
The answer to that question is no. Whilst the temperature changes were indeed gradual, easy to cope with for fauna, the precipitation changes were overnight, and that was the real killer. In Siberia the dry steppes changed in marshed and swamps in the Preboreal, following the Younger Dryas causing the last mammoths to go extinct around 11,200 Cal BP (9600 carbion years), The American megafauna perished at the beginning of the Younger Dryas, around 12500 Cal BP (ca 10500 carbon years) with an extreme dry period.
Our paper regarding this theory is under review of Quartenary International.
Non calor sed umor.
Andre
CCNet is a scholarly electronic network edited by Benny Peiser. To subscribe, send an e-mail to listserver@livjm.ac.uk ("subscribe cambridge-conference").
Comments:
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The moa in NZ died out shortly after the arrival of Maori colonists in, probably, the late 1200s AD. Nothing to do with ice ages. Giant flightless birds must be particularly easy to exterminate - death by a thousand omelettes.
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