Editing Little Ice Age (section)

==== Destruction of native populations and biomass of the Americas ====
William Ruddiman further hypothesized that a [[population history of the indigenous peoples of the Americas|reduced population in the Americas]] after European contact started in the 16th century could have had a similar effect.<ref name="Ravilious2006">{{Cite news |last=Ravilious |first=Kate |title=Europe's chill linked to disease |date=27 February 2006 |publisher=BBC |url=http://news.bbc.co.uk/1/hi/sci/tech/4755328.stm}}</ref><ref name="Ruddiman2003">{{cite journal |last1=Ruddiman |first1=William F. |year=2003 |title=The Anthropogenic Greenhouse Era Began Thousands of Years Ago |journal=[[Climatic Change (journal)|Climatic Change]] |volume=61 |issue=3 |pages=261–293 |citeseerx=10.1.1.651.2119 |doi=10.1023/B:CLIM.0000004577.17928.fa |bibcode=2003ClCh...61..261R |s2cid=2501894}}</ref> In a similar vein, Koch and others in 1990 suggested that as European conquest and disease brought by Europeans killed as many as 90% of Indigenous Americans, around 50 million hectares of land may have returned to a wilderness state, causing increased carbon dioxide uptake.<ref>David Graeber and David Wendgrow, "The Dawn of Everything" (New York: Farrar, Straus and Giroux, 2021) p. 258.</ref> Other researchers have supported depopulation in the Americas as a factor and have asserted that humans cleared considerable amounts of forest to support agriculture there before the arrival of Europeans brought on a population collapse.<ref name=ams1>{{Cite journal |doi=10.1175/EI157.1 |bibcode=2006EaInt..10k...1F |title=Evidence for the Postconquest Demographic Collapse of the Americas in Historical CO2 Levels |journal=[[Earth Interactions]] |volume=10 |issue=11 |pages=1 |last1=Faust |first1=Franz X. |last2=Gnecco |first2=Cristóbal |last3=Mannstein |first3=Hermann |last4=Stamm |first4=Jörg |year=2006 |url=https://elib.dlr.de/43708/1/Faust_et_al_2006.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://elib.dlr.de/43708/1/Faust_et_al_2006.pdf |archive-date=2022-10-09 |url-status=live }}</ref><ref>Richard J. Nevle ''et al''., "Ecological-hydrological effects of reduced biomass burning in the neotropics after A.D. 1500," ''Geological Society of America Meeting'', Minneapolis MN, 11 October 2011. [http://gsa.confex.com/gsa/2011AM/finalprogram/abstract_196092.htm abstract] {{Webarchive|url=https://web.archive.org/web/20190815074531/https://gsa.confex.com/gsa/2011AM/finalprogram/abstract_196092.htm|date=15 August 2019}}. Popular summary: "[http://www.sciencenews.org/view/generic/id/335168/title/Columbus_arrival_linked_to_carbon_dioxide_drop Columbus' arrival linked to carbon dioxide drop: Depopulation of Americas may have cooled climate]," ''Science News,'' 5 November 2011. (access date 2 January 2012).</ref>

Richard Nevle, Robert Dull and colleagues further suggested not only that anthropogenic forest clearance played a role in reducing the amount of carbon sequestered in [[Neotropical realm|Neotropical]] forests but also that human-set fires played a central role in reducing biomass in Amazonian and Central American forests before the arrival of the Europeans and the concomitant spread of diseases during the [[Columbian exchange]].<ref>{{Cite journal|last1=Nevle|first1=Richard J.|last2=Bird|first2=Dennis K.|date=7 July 2008|title=Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest|journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]]|volume=264|issue=1|pages=25–38|doi=10.1016/j.palaeo.2008.03.008|issn=0031-0182|bibcode=2008PPP...264...25N}}</ref><ref name="Dull 755–771">{{Cite journal |last1=Dull |first1=Robert A. |last2=Nevle |first2=Richard J. |last3=Woods |first3=William I. |last4=Bird |first4=Dennis K. |last5=Avnery |first5=Shiri |last6=Denevan |first6=William M. |date=31 August 2010 |title=The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing |journal=Annals of the Association of American Geographers |volume=100 |issue=4 |pages=755–771 |doi=10.1080/00045608.2010.502432 |issn=0004-5608 |s2cid=129862702}}</ref><ref name="Holocene_20110801">{{Cite journal |last1=Nevle |first1=R. J. |last2=Bird |first2=D. K. |last3=Ruddiman |first3=W. F. |last4=Dull |first4=R. A. |date=1 August 2011 |title=Neotropical human–landscape interactions, fire, and atmospheric CO2 during European conquest |journal=[[The Holocene]] |language=en |volume=21 |issue=5 |pages=853–864 |bibcode=2011Holoc..21..853N |doi=10.1177/0959683611404578 |issn=0959-6836 |s2cid=128896863}}</ref> Dull and Nevle calculated that reforestation in the tropical biomes of the Americas alone from 1500 to 1650 accounted for net [[carbon sequestration]] of 2–5 [[petagram|Pg]].<ref name="Dull 755–771"/> Brierley conjectured that the European arrival in the Americas caused mass deaths from epidemic disease, which caused much abandonment of farmland. That caused much forest to return, which sequestered more CO<sub>2</sub>.<ref name="Brierley  et al 2019"/> A study of sediment cores and soil samples further suggests that CO<sub>2</sub> uptake via reforestation in the Americas could have contributed to the LIA.<ref name="Bergeron2008">{{Cite news |last=Bergeron|first=Louis |title=Reforestation helped trigger Little Ice Age, researchers say |date=17 December 2008 |publisher=Stanford News Service |url=http://news-service.stanford.edu/news/2009/january7/manvleaf-010709.html}}</ref> The depopulation is linked to a drop in CO<sub>2</sub> levels observed at [[Law Dome]], Antarctica.<ref name=ams1/>

However, the hypothesis is criticized on the grounds that the kind of [[agroforestry]] practiced by the pre-Columbian farmers in South America didn't actually result in a large-scale deforestation typical for modern agriculture so the reforestation shouldn't have had such a huge effect.<ref>{{Cite journal |last1=Watling |first1=Jennifer |last2=Iriarte |first2=José |last3=Mayle |first3=Francis E. |last4=Schaan |first4=Denise |last5=Pessenda |first5=Luiz C. R. |last6=Loader |first6=Neil J. |last7=Street-Perrott |first7=F. Alayne |last8=Dickau |first8=Ruth E. |last9=Damasceno |first9=Antonia |last10=Ranzi |first10=Alceu |date=2017-02-21 |title=Impact of pre-Columbian "geoglyph" builders on Amazonian forests |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=8 |pages=1868–1873 |doi=10.1073/pnas.1614359114 |doi-access=free |issn=0027-8424 |pmc=5338430 |pmid=28167791|bibcode=2017PNAS..114.1868W }}</ref>