Pre-Columbian fire management and control of climate-driven floodwaters over 3,500 years in southwestern Amazonia

Abstract

In landscapes that support economic and cultural activities, human communities actively manage environments and environmental change at a variety of spatial scales that complicate the effects of continental-scale climate. Here, we demonstrate how hydrological conditions were modified by humans against the backdrop of Holocene climate change in southwestern Amazonia. Paleoecological investigations (phytoliths, charcoal, pollen, diatoms) of two sediment cores extracted from within the same permanent wetland, ∼22 km apart, show a 1,500-y difference in when the intensification of land use and management occurred, including raised field agriculture, fire regime, and agroforestry. Although rising precipitation is well known during the mid to late Holocene, human actions manipulated climate-driven hydrological changes on the landscape, revealing differing histories of human landscape domestication. Environmental factors are unable to account for local differences without the mediation of human communities that transformed the region to its current savanna/forest/wetland mosaic beginning at least 3,500 y ago. Regional environmental variables did not drive the choices made by farmers and fishers, who shaped these local contexts to better manage resource extraction. The savannas we observe today were created in the post-European period, where their fire regime and structural diversity were shaped by cattle ranching.

A Review of Archaeological and Paleoecological Radiocarbon Dating in Bolivia

“…Similar results were produced in Laguna La Luna contiguously located to a forest island dominated by cacao trees, which were likely planted relatively late in pre-Columbian times (Carson et al, 2016). More recent research, from the Quinato wetland near Santa Ana de Yacuma, has verified that hydrological engineering might have helped to manage the increasing precipitation in the region over the course of the Late Holocene (Duncan et al, 2021). Additionally, research in lakes around some raised field systems such as Laguna El Cerrito and Laguna Frontera near the site of El Cerrito and a large complex of raised fields has allowed reconstructing the vegetation dynamics associated with their use as well as indirectly time when they were likely used (Whitney et al, 2014).…”

Incorporating a palaeo-perspective into Andean montane forest restoration

“…Prior to European arrival in the Americas (CE 1492), it has been estimated that c.60 million people lived in social structures from small groups of hunter gathers to vast civilisations (Koch et al, 2019). For thousands of years people domesticated crops, moulded landscapes to fit their needs and drove changes in ecosystems (Montoya et al, 2020;Duncan et al, 2021). However, within a century as much as 90% (c. 54 million people) of the population were dead as the result of European conquest and imported diseases (Koch et al, 2019).…”