A palaeoecological perspective on the transformation of the tropical Andes by early human activity

Abstract

Palaeoecological records suggest that humans have been in the Andes since at least 14 000 years ago. Early human impacts on Andean ecosystems included an increase in fire activity and the extinction of the Pleistocene megafauna. These changes in Andean ecosystems coincided with rapid climate change as species were migrating upslope in response to deglacial warming. Microrefugia probably played a vital role in the speed and genetic composition of that migration. The period from ca 14 500 to 12 500 years ago was when novel combinations of plant species appeared to form no-analogue assemblages in the Andes. By 12 000 years ago most areas in what are today the Andean grasslands were being burned and modified by human activity. As the vegetation of these highland settings has been modified by human activity for the entirety of the Holocene, they should be regarded as long-term manufactutred landscapes. The sharp tree lines separating Andean forests from grasslands that we see today were probably also created by repeated burning and owe their position more to human-induced fire than climatic constraints. In areas that were readly penetrated by humans on the forested slopes of the Andes, substantial modification and settlement had occurred by the mid-Holocene. In hard-to-reach areas, however, the amount of human modification may always have been minimal, and these slopes can be considered as being close to natural in their vegetation. This article is part of the theme issue ‘Tropical forests in the deep human past’.

Tropical forests in the deep human past

“…This appears to have initially taken place along river banks and drier fringes of the lowland and montane forest zone. However, within a few millennia, human occupation pushed deeper into the Amazon forest, primarily along river networks, although archaeological evidence may be biased to such accessible sites [ 19 , 20 ]. Human occupation modes ranged from hunting and gathering to agricultural systems which were based either on locally originated domestications such as manioc and squashes, or imported from Mesoamerica, such as maize.…”

“…In this volume, Bush et al . [ 19 ] and Nascimento et al . [ 20 ] synthesize paleoecological data to paint detailed pictures of the timing and ecological impacts of early human arrival in the tropical Andes and Amazon lowlands, respectively.…”

“…Bush and colleagues suggest these extensive grasslands should be regarded as long-term anthropogenic Holocene landscapes, and likewise the sharp treeline between the forests of the Andean flank and the grasslands should be regarded as anthropogenic rather than climate-defined. These dense forests of the montane flank were probably less settled than the flatter and drier upland regions for both topographic and climate reasons, though by the mid-Holocene accessible regions of the montane forest zone were substantially modified and settled [ 19 ].…”

“…By examining paleoecological evidence from lakes across the Andes, Bush et al . [ 19 ] describe the timing of this transition, with widespread demise of megafauna around 12.5 ka, soon after an increase of fire. They propose the megafauna were stressed by the rapid warming and wet conditions of the deglaciation and population recovery was prevented by hunters who transformed the high Andean landscape through burning.…”

“…The extent to which Amazonia is a cultural landscape with a significant long-term human footprint is still disputed, however [ 19 ]. Nascimento et al .…”