The adoption of agropastoralism and increased ENSO frequency in the Andes

• Published in: Quaternary science reviews 2020-09, Vol.243, p.106471, Article 106471
• Main Authors: Nascimento, M.N., Mosblech, N.A.S., Raczka, M.F., Baskin, S., Manrique, K.E., Wilger, J., Giosan, L., Benito, X., Bush, M.B.
• Format: Article
• Language: English
• Subjects: Domestication; El Niño Southern Oscillation; Human settlement; Maize; Mid-holocene dry event; Paleoecology; Pollen
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2020.106471

Humans have been present in the Andes since about 12,000 calibrated years before present (cal yr BP), transitioning from hunter-gatherers to agropastoralist societies in the mid-Holocene. Yet, the timing and effects of this change in behavior on the ecosystem are largely unknown. Using titanium from XRF analysis, loss-on-ignition (LOI), fossil pollen, Sporormiella, and charcoal, we present a high-resolution 12,000-yr paleoecological history of Lake Llaviucu, a mid-elevation lake in the Ecuadorian Andes. For the entire period of study, humans were active in this landscape, with signs of agropastoralism being present since c. 6100 cal yr BP. Apparent ENSO activity, inferred from titanium inputs to the sediment is also heightened at c. 6100 cal yr BP. A trajectory of increasing landuse seems to have peaked in terms of maize production between c. 2900 and 800 cal yr BP. Thereafter, larger abundances of Sporormiella spores suggest that pastoralism was of increasing importance; a pattern disrupted by European arrival. Apparent peaks in El Niño Southern Oscillation (ENSO) appears to be linked to fire and maize frequency. We investigated the relationship between the Lake Llaviucu record and that of nearby Lake Pallcacocha, which is often cited as providing a regional ENSO history. •Humans were present in this landscape since before 12,000 cal yr BP, with signs of agropastoralism being present only after c. 6100 cal yr BP.•Apparent ENSO activity increases when the first signs of agropastoralism appear.•Landuse seems to have peaked in terms of maize production and Sporormiella between 2900 and 800 cal yr BP, a pattern disrupted by European arrival.•Peaks in El Niño Southern Oscillation (ENSO) appear to be linked to fire and maize frequency.•We contend that these are human-manufactured landscapes in that the balance of species has been continuously altered by human actions.