Evidence for the Postconquest Demographic Collapse of the Americas in Historical CO2 Levels

Abstract

This article promotes the hypothesis that the massive demographic collapse of the native populations of the Americas triggered by the European colonization brought about the abandonment of large expanses of agricultural fields soon recovered by forests, which in due turn fixed atmospheric CO2 in significant quantities. This hypothesis is supported by measurements of atmospheric CO2 levels in ice cores from Law Dome, Antarctica. Changing the focus from paleoclimate to global population dynamics and using the same causal chain, the measured drop in historic atmospheric CO2 levels can also be looked upon as further, strong evidence for the postconquest demographic collapse of the Americas.

Colonization of the Americas, ‘Little Ice Age’ climate, and bomb-produced carbon: Their role in defining the Anthropocene

“…Like other postulates (Faust et al, 2006), they associated this CO 2 dip with depopulation in the Americas following European colonization: thus, Lewis and Maslin regard it as an anthropogenic marker of "transoceanic movement of species [that] is a clear and permanent geological change to the Earth system." However, the magnitude of the CO 2 fluctuation cited by Lewis and Maslin (2015) is not outside the range of natural Holocene variability (Figure 1).…”

Neotropical human–landscape interactions, fire, and atmospheric CO2 during European conquest

“…The decrease near 1600 is the most prominent step in a noisy downward CO 2 trend over several centuries. Several studies have inferred that natural forcing can explain the CO 2 trend (Böhm et al, 2002;Etheridge et al, 1996;Francey et al, 1999;Hunt, 1998;Joos et al, 1999;Trudinger et al, 1999;von Storch et al, 2004), but others have suggested that reforestation and carbon sequestration tied to demographic collapse in the Americas also played a significant role in this unusually rapid and steep drop (Dull et al, 2010;Faust et al, 2006;Ferretti et al, 2005;Nevle and Bird, 2008;Ruddiman, 2003).…”

“…Although the association of fire with prehistoric land use and agriculture in Neotropical forest biomes ( Figure 1) is well established (Bush et al, 2008;Mayle and Power, 2008;Piperno and Pearsall, 1998), the extent to which humans impacted biomass burning at regional scales remains controversial (Bush et al, 2008;Dull et al, 2010;Faust et al, 2006;Ferretti et al, 2005;Houweling et al, 2008;Marlon et al, 2008;Mayle and Power, 2008;Mischler et al, 2009;Nevle and Bird, 2008). Neotropical biomass burning reconstructions based on soil and sedimentary charcoal records by Bush et al (2008), Marlon et al (2008), and Nevle and Bird (2008) document similar temporal variations in regional biomass burning ( Figure 2), but interpretations diverge regarding the causes of these variations.…”

The early anthropogenic hypothesis: Challenges and responses

“…For a population of 55 million the total amount of deforestation just before European arrival would have been 1.1 million km 2 . Faust et al [2006] arrived at a nearly identical value. At a mean carbon density of 13 Gt C per million km 2 [ Houghton , 1999], total deforestation by 1500 would have produced ∼14 Gt C. This estimate exceeds that of DeFries et al [1999] for pre‐1850 deforestation by ∼8 Gt C.…”