Periodic Reporting for period 1 - AHEAD (A Human and Environmental history of the Atacama Desert: understanding ecological and archaeological interactions in arid areas of South America)
Periodo di rendicontazione: 2018-09-01 al 2020-08-31
AHEAD was designed to analyse the interactions between human societies and South American hyperarid environments through the study of charcoal and wood remains from archaeological sites and natural deposits. The choice of desert areas is related to the very good preservation of vegetal remains both in archaeological sites and in natural locations and to the low diversity of the vegetation that permit to observe clearly the evolution of the environment and of the human practices. This project encompasses a period between the end of Pleistocene and Late Holocene in different locations of South American desert in Chile (Atacama Desert), Peru (coastal desert) and Argentina (altitude desert). It includes different societies: nomads, (hunter-gatherers), and sedentary (Formative societies and modern occupations).
The results obtained with AHEAD permitted to compare the fuelwood economy in different societies and region in desert areas and to observe the evolution of the vegetation and the presence of water (by using isotopic analyses of carbon). The results obtained here show that the vegetation used as fuelwood is mostly local and available at short distance. For the hunter-gatherer’s period, all the species are native but for the more recent period, introduced species, locally presented and sometimes cultivated are also used. The evolution in water availability, registered with isotopic analyses of carbon, shows that it as a low impact on the choice of species used as fuel and that the evolution in practices such as irrigation and agriculture have a more important impact.
The results obtained with AHEAD permitted to compare the fuelwood economy in different societies and region in desert areas and to observe the evolution of the vegetation and the presence of water (by using isotopic analyses of carbon). The results obtained here show that the vegetation used as fuelwood is mostly local and available at short distance. For the hunter-gatherer’s period, all the species are native but for the more recent period, introduced species, locally presented and sometimes cultivated are also used. The evolution in water availability, registered with isotopic analyses of carbon, shows that it as a low impact on the choice of species used as fuel and that the evolution in practices such as irrigation and agriculture have a more important impact.
During this project, 7446 charcoals and 117 wood samples have been determined using a predetermined methodology that we used before (Joly et al. 2017). Charcoals were cut with a scalpel to observe 3 plans. For the wood, it was boiled to soften and cut to prepare thin cut. They were identified using a microscope (BX53) and a binocular microscope. To compare their anatomy, we used the collection of references created before this project that was supplemented with new references from our fieldwork in Chile and thanks to the new collaboration with archaeologists working in Peru and Argentina (fig.1). We also used different Atlas of wood anatomy. About 35 different taxa were identified, most of them are native.
From these identified wood and charcoal, 147 samples have been selected. Using established protocols, isotope analysis of charcoal (δ13Cchar) and wood samples (δ13Cwood) were realised. The δ13C value is related to climatic variables that affect plant water availability, (Evapotranspiration and precipitation) and could serve as a direct proxy for rainfall variation, and/or water provenance. The results show a difference between the different period, locations and species with a better water availability at the end of Pleistocene.
From these identified wood and charcoal, 147 samples have been selected. Using established protocols, isotope analysis of charcoal (δ13Cchar) and wood samples (δ13Cwood) were realised. The δ13C value is related to climatic variables that affect plant water availability, (Evapotranspiration and precipitation) and could serve as a direct proxy for rainfall variation, and/or water provenance. The results show a difference between the different period, locations and species with a better water availability at the end of Pleistocene.
AHEAD represented an opportunity to examine long-term human adaptations to extreme environments in the past and is the first study of human and environment interaction through fuelwood analysis that combines traditional taxonomic approaches with biomolecular techniques in south American deserts. It revealed the long-term use of fuelwood resources in negotiating human survival in desert areas, from foraging subsistence to colonial sites. This combination of location and environment provided the opportunity to fully assess how human populations interacted with their environments, and to assess both the impact of people on the desert ecology, and how communities have responded to past climatic fluctuations.