Pinter et al., on a paper recently published in Quaternary Science Reviews, have reviewed several studies about the changes in vegetation and fire patterns in the Americas between 13.000 and 8.000 yr BP. The transition from the Pleistocene to the Holocene saw a climate change that marked the end of the last glaciation. During the Holocene, the ice melted, the see level raised and, of course, the vegetation changed. Therefore, the changes in paleoecological records of this period - like pollen and charcoal in lake sediments – have been interpreted as exclusive evidence of climate change. However, the problem is that during this same period of climatic change, people colonized America and also transformed the environment. We know that people can have a negative impact on the environment. Pinter et al. report several examples: “In Australia, human colonization ca 50,000–45,000 BP was accompanied by extinction of 90% of large fauna and the rapid decline of rainforest gymnosperms and other fire-intolerant plant taxa and by sharp increases in charcoal […] Tasmania was colonized 5–10 kyrs later than mainland Australia, and megafaunal extinctions and fire-driven devegetation and erosion also occurred 5–10 kyrs later.”
Why should it have been any different in America? People used fire and hunted large herbivores, maybe bringing them to the extinction. The extinction of the megafauna and the use of fire had an important impact on the vegetation. So, the main conclusion of their review is that climate is not the “universal independent variable” determining environmental change. People also played an important role.
But where and when? And here comes the importance of archaeological research and the study and reconstruction of past human-environment interactions. We need to set the geographical and chronological limits of human presence in the Americas in order to be able to interpret the paleoecological archives with any accuracy. This is extremely important in the Amazon Basin, where evidence of early human occupation is scarce. We need to address a fundamental question: Were there no people living in Amazonia 10.000 yr. BP or have we simply been unable to find their archaeological remains yet?
In Science they have just published a paper that dates back the first pre-Clovis occupation at between ~13.2 and 15.5 thousand years ago.
ReplyDeletehttp://www.sciencemag.org/content/331/6024/1599.abstract
published today on NATURE, a good summary of the debate about early human influence on Holocene climate. Thomas Stocker, from Bern University seem to be a big player here :-)
ReplyDeletehttp://www.nature.com/news/2011/110325/full/news.2011.184.html
Hola Umberto-Mann,
ReplyDeleteinteresting stuff, this. And a really good introduction for la isla, jaja. Even though in my opinion la isla shows that people WERE there, and not so much that they were to BLAME for the obviously strong environmental impacts at the P-H transition..., huh? The Pinter paper seems like a good paper, will have a look, but got to be careful with the Australian example: there is still ample discussion going on about the WHEN and HOW people arrived down under, and their impact is far from being understood (you will be able to find a huge number of papers arguing for and against the aboriginals...): in the context it is interesting to know, that all of those huge inland lakes in the Australian desert (Lake Eyre, Frome etc) just around 45-50 ka were FULL for the last time since. So, maybe climate is to blame for the extinction of the poor megafauna? In most of Australia, there is no evidence at all for humans until much later (25 ka ...)?? hmm, unfortunately in Moxos we dont have huge paleolakes, but its full of mega-meanders which wait to be studied... :-)
Great posts Umberto! I agree in part with Henne, I think the poor megafauna were hit with a "double-whammy" (that may be a very American reference). Major climate change, plus these crazy people hunting them. I don't think it can be attributed to a single cause (climate or humans), it's another one of those historical events where multiple forces collide and create a perfect storm.
ReplyDeleteWe can talk about this person very soon!!! See you in a few days Umberto!
Enjoy the conference!
ReplyDeleteThis is a very interesting subject. I first thought of it when visiting a paleontological museum in Colombia, surrounded by all this amazing, huge, and unknown fauna (unknown to me, of course). All those species needed millions of years to form, and yet they seem to disappear in a flash, mostly in the last deglaciation. That sounds a bit fortuituous. Daniel.
ReplyDeleteI think Daniel put forward a good point. Why haven’t the magafauna adapted to the climate change? It was a few degrees increase in the average temperature; the magafauna had plenty of space and time to migrate to different latitudes or elevations. Probably climate put magafauna under stress but people did the final job. I think.
ReplyDeletewell, yes, good point.. why did those creatures just didnt make it...? but since when did they make it? what do we know about their evolution?? is it that they "needed millions of years to form"? and, what if the Holocene really is "unprecedented" from a climatic point of view? maybe not the warmest, but the driest?? many good papers around saying exactly this...? in any sense, wouldnt surprise me, if WE are to blame anyway, just dont see the evidence for it, certainly not on a global scale... so lets not compare Australia and (loved) SA :-)
ReplyDeletecheers H