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The real reason the woolly mammoth died out31/08/2010 01:06:40New research suggests dwindling green pastures not hunting killed off Ice Age mega-mammals August 2010: The decline of woolly mammoths, woolly rhino and the cave lion may have been because of massive reduction in grasslands and the spread of forests, according to the latest research.
Durham University scientists are challenging the theory that human beings were the primary cause of the extinction of mammals through hunting, competition for land and increased pressure on habitats. The research is part of the most comprehensive study to date of Northern Hemisphere climate and vegetation during and after the height of the last Ice Age, 21,000 years ago. It shows that, over a huge part of the Earth's surface, there was a massive decline in the productivity and extent of grasslands due to climatic warming and the spread of forests. Dawning of warm interglacial period sealed animals' fate The decrease in productivity and extent of grassland is likely to have been the major contributor to the extinction of many large mammals across most of northern Eurasia and north-western North America by about 11,400 years ago, the onset of the present warm interglacial period. Although some species held on for several thousand years longer in very limited localities, their fate had effectively been sealed. They found it increasingly difficult to find food ‘The change from productive grasslands across large areas of northern Eurasia, Alaska and Yukon to less productive tundra-like habitats had a huge effect on many species, particularly on the large herbivores such as the woolly rhinoceros and woolly mammoth. Mammoths and other mega-mammals found it increasingly difficult to find food. ‘We believe that the loss of food supplies from productive grasslands was the major contributing factor to the extinction of these mega-mammals.' A model for the effects of modern-day climate change Prof Huntley said: ‘This was a time of major environmental change and losses of habitat that may have led to the extinction of herbivores and other mega-species that roamed many parts of the planet. This is a model for what may happen as a result of rapid climate change over the next century linked to human activity. It is food for thought in these times of global warming and human-induced habitat change. There may well be a lesson to learn.'
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But wait a minute.
It is reasonably clear that on the continents, the figures don't tally.
Humans were in Australia by 60,000 years ago, long before the mega-mammals disappeared; and humans were in the Americas possibly tens of thousands, maybe 100,000, of years before 13,000 years ago.
Madagascar and NZ are different in that they were islands and so much more vulnerable to what were, unquestionably, agriculturally based humans, not hunter-gatherers. Those extinctions took place in the last few 1,000 years.
What none of the carnage theories care to explain, ever, is WHY humans would have wanted to go on a rampaging spree. Hunter-gatherers are punctilious to a high degree in respecting their prey species, holding them in the tenderest regard, and showing careful respect to their generosity by trying their hardest never to waste their flesh and bones.
It always strikes me that the Wipe-out Theories say far more about modern (free-market capitalist) humans and their predispositions that ever they do about ancient human communities.
Certainly the actual evidence rarely gets in the way of a good old catastrophe scenario, where we get to ease our consciences at the expense of long-gone peoples who are not around to speak for themselves, i.e. we've always been killing stuff HAVEN'T we? So - on with the destruction!
Er, no, actually.
Posted by: Dominic Belfield | 10 Sep 2010 15:47:09
Glossing over the fact that woolly mammoths are not even mentioned by Huntley in the paper in Quaternary Science Reviews (29 (2010) 2604-2618) the vegetation changes do, as he says, raise the issue about the fate of the Pleistocene megafauna, and their presumed fate in the Holocene at the hands of humans.
The issue has particular resonance for the prevailing view of the conservation industry in Britain, who take comfort that their highly interventionist management approach to hold back the dynamism of wild nature is consistent with the effects of great herds of these herbivores chomping up the countryside. That we ended up with wildwood covering most of Britain after the last glaciation is to them but an aberration in the absence of these exterminated megafauna.
The literature seems to see-saw as to why the mega-herbivores disappeared. Thus one article that charts Pleistocene climate change as a way of differentiating human impacts from other drivers of ecological change shows that 90% of Australia’s large mammals were extinct by around 45 ka. An analysis of faunal data from the Naracoorte Caves in south eastern Australia shows that, despite significant population fluctuations driven by glacial-interglacial cycling, the species composition of the mammal fauna was essentially stable for 500 k.y. before the late Pleistocene extinctions. Larger species declined during a drier interval between 270 and 220 ka, likely reflecting range contractions away from Naracoorte, but they then recovered locally, persisting well into the late Pleistocene. Because the cave formation records and prior faunal response imply that local conditions should have been favorable for megafauna until at least 30 ka, climate change is unlikely to have been the principal cause of the extinctions.
Prideaux et al (2007) Mammalian responses to Pleistocene climate change in southeastern Australia, Geology 35:33-36
A very recent research paper yet again ties megafaunal extinction in N. America to the appearance of modern humans e.g.
“We compute those baselines for mammals of temperate North America, using a sampling-standardized rich fossil record to reconstruct species-area relationships for a series of time slices ranging from 30 million to 500 years ago. We show that shortly after humans first arrived in North America, mammalian diversity dropped to become at least 15%–42% too low compared to the “normal” diversity baseline that had existed for millions of years. While the Holocene reduction in North American mammal diversity has long been recognized qualitatively, our results provide a quantitative measure that clarifies how significant the diversity reduction actually was.”
“Our results provide a quantitative assessment of what has long been primarily a qualitative observation: namely, the decline in mammal diversity that occurred as human presence first began to dominate the North American landscape. We demonstrate that this decline represented a 15–42% loss (depending on biogeographic province) in mammal species richness. Therefore, the diversity baseline we are at today already is well below the “normal” biodiversity baseline for North American mammals, if we define “normal” as the condition that prevailed through most of the millions of years modern mammal families have been on Earth.”
Carrasco et al (2009) Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline. PLoS ONE 4(12): e8331
Megafaunal carnage throughout the world’s history seems to correlate with the arrival of modern man, from the 40-50,000 years ago in Australia, 13,000 years ago in the Americas, and for other extinctions to the more recent oceanic explorations that saw the arrival 2000 years ago in Madagascar and 1000 years ago in New Zealand. In the Americas, as in New Zealand and Australia, the extinction of species was only compounded by the arrival of Euro-settlers and their agriculture. I would only be too pleased if human-caused extinction were not the only reason, at least in the case of the megafauna, because it would take away the crutch of the conservation industry.
Posted by: Mark Fisher | 31 Aug 2010 15:15:59