[MCN] Climate has capacity to reduce human population: Case history from So. America

Lance Olsen lance at wildrockies.org
Wed May 22 15:06:21 EDT 2019

Scientific Reports  Published: 09 May 2019 <https://www.nature.com/articles/s41598-019-43086-w#article-info>

Widespread population decline in South America correlates with mid-Holocene climate change
Philip Riris <https://www.nature.com/articles/s41598-019-43086-w#auth-1> & Manuel Arroyo-Kalin <https://www.nature.com/articles/s41598-019-43086-w#auth-2> 

Abstract [ OPEN ACCESS ]
https://www.nature.com/articles/s41598-019-43086-w <https://www.nature.com/articles/s41598-019-43086-w>

Quantifying the impacts of climate change on prehistoric demography is crucial for understanding the adaptive pathways taken by human populations. Archaeologists across South America have pointed to patterns of regional abandonment during the Middle Holocene (8200 to 4200 cal BP) as evidence of sensitivity to shifts in hydroclimate over this period. We develop a unified approach to investigate demography and climate in South America and aim to clarify the extent to which evidence of local anthropic responses can be generalised to large-scale trends. We achieve this by integrating archaeological radiocarbon data and palaeoclimatic time series to show that population decline occurred coeval with the transition to the initial mid-Holocene across South America. Through the analysis of radiocarbon dates with Monte Carlo methods, we find multiple, sustained phases of downturn associated to periods of high climatic variability. A likely driver of the duration and severity of demographic turnover is the frequency of exceptional climatic events, rather than the absolute magnitude of change. Unpredictable levels of tropical precipitation had sustained negative impacts on pre-Columbian populations lasting until at least 6000 cal BP, after which recovery is evident. Our results support the inference that a demographic regime shift in the second half of the Middle Holocene were coeval with cultural practices surrounding Neotropical plant management and early cultivation, possibly acting as buffers when the wild resource base was in flux.

“The death knell for the grizzly in the Southwest was tolled not by a church bell but by a train whistle.”

“Changing economic conditions, new homesteading laws, and cheap rail travel resulted in an ever-increasing 
influx of settlers, who eventually penetrated to the remotest corners of the region.”

David E. Brown.  The grizzly in the southwest. University of Oklahoma Press. 1985. p. 97

“We found that brown bear populations in Europe lost connectivity since Neolithic times, when farming communities 
expanded ... In central Italy, this resulted in a 40-fold population decline.”

Andrea Benazzo et al. Survival and divergence in a small group: The extraordinary genomic history of the endangered 
Apennine brown bear stragglers. PNAS Early Edition Published online before print October 24 2017

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