Cosmogenic in situ 14C-10Be reveals abrupt Late Holocene soil loss in the Andean Altiplano

Kristina Hippe,Gerold Zeilinger,Daniel Søndergaard Skov,Maarten Lupker,John D Jansen,Christof Vockenhuber,David Lundbek Egholm,José Mariano Capriles,Marcus Christl,Florian Kober,Susan Ivy-Ochs,Colin Maden

doi:10.1038/s41467-021-22825-6

Abstract

Soil sustainability is reflected in a long-term balance between soil production and erosion for a given climate and geology. Here we evaluate soil sustainability in the Andean Altiplano where accelerated erosion has been linked to wetter climate from 4.5 ka and the rise of Neolithic agropastoralism in the millennium that followed. We measure in situ cosmogenic 14C directly on cultivated hilltops to quantify late Holocene soil loss, which we compare with background soil production rates determined from cosmogenic 26Al and 10Be. Our Monte Carlo-based inversion method identifies two scenarios to account for our data: an increase in erosion rate by 1–2 orders of magnitude between ~2.6 and 1.1 ka, or a discrete event stripping ~1–2 m of soil between ~1.9 and 1.1 ka. Coupled environmental and cultural factors in the Late Holocene signaled the onset of the pervasive human imprint in the Andean Altiplano seen today.

Highlights

Soil sustainability is reflected in a long-term balance between soil production and erosion for a given climate and geology
The Titicaca Basin on the Andean Altiplano is an early centre of agricultural development and its archaeology and palaeoclimate have long been in the research spotlight[19,20,21,22,23,24,25,26]
The debate is sustained in part, because no evaluation of soil sustainability has ever been conducted and the erosional dynamics arising from climate and land use remain unquantified

Summary

Introduction

Soil sustainability is reflected in a long-term balance between soil production and erosion for a given climate and geology. Given that long-term soil production and erosion tend towards a balance, a compelling evaluation of soil sustainability is to quantify and compare erosion with geological background rates[5]. To this end, vital gains have been made by extracting sedimentary records from floodplains, lakes and estuaries[6,7]. Climatic variations since the last glacial–interglacial transition were a key driver of the technological and social transformations that spawned farming across multiple centres during the Neolithic[12,13,14] This link implies humans were exploiting new capacities in their environment and it underscores connections between climate and the impacts of land use on soil, plants and the atmosphere[9,10,15,16,17,18]. The span of half-lives (5.7 kyr, 0.7 Myr and 1.4 Myr for 14C, 26Al and 10Be, respectively) allows resolving erosion rates (white square) 15–30 km from the Desaguadero valley; 18 regional catchments with basin-wide erosion rates (grey shading, Supplementary Table 6); and 17 archaeological sites (white diamonds) radiocarbon-dated to the start of Formative Period in the Titicaca Basin[44]

Methods

Results

Conclusion