Ecosystem impacts by the Ancestral Puebloans of Chaco Canyon, New Mexico, USA.

David L Lentz,Nicholas P Dunning,Kenneth B Tankersley,Lewis A Owen,Venicia Slotten,Jon-Paul Mccool,Stephen Plog,John G Jones,Samantha G Fladd,Vernon L Scarborough,Cory J Perfetta,Brooke Crowley,Christopher Carr,Peter F Biehl

doi:10.1371/journal.pone.0258369

Abstract

The Ancestral Puebloans occupied Chaco Canyon, in what is now the southwestern USA, for more than a millennium and harvested useful timber and fuel from the trees of distant forests as well as local woodlands, especially juniper and pinyon pine. These pinyon juniper woodland products were an essential part of the resource base from Late Archaic times (3000–100 BC) to the Bonito phase (AD 800–1140) during the great florescence of Chacoan culture. During this vast expanse of time, the availability of portions of the woodland declined. We posit, based on pollen and macrobotanical remains, that the Chaco Canyon woodlands were substantially impacted during Late Archaic to Basketmaker II times (100 BC–AD 500) when agriculture became a major means of food production and the manufacture of pottery was introduced into the canyon. By the time of the Bonito phase, the local woodlands, especially the juniper component, had been decimated by centuries of continuous extraction of a slow-growing resource. The destabilizing impact resulting from recurrent woodland harvesting likely contributed to the environmental unpredictability and difficulty in procuring essential resources suffered by the Ancestral Puebloans prior to their ultimate departure from Chaco Canyon.

Highlights

The first human occupants of Chaco Canyon, located in what is the southwestern region of the United States (Fig 1), arrived as early as Paleoindian times, ~10,000 BC (S1 Table in S1 File)
Before 600 BC the juniper and pine pollen readings (S4 Table in S1 File; Fig 5) were at 20% and 12% respectively, which is characteristic of a robust pinyon juniper woodland [34]
Our findings agree with previous studies that hypothesize the Ancestral Puebloans had a significant impact on the pinyon juniper woodlands (PJW) that once comprised the dominant vegetation of Chaco Canyon

Summary

Introduction

The first human occupants of Chaco Canyon, located in what is the southwestern region of the United States (Fig 1), arrived as early as Paleoindian times, ~10,000 BC (S1 Table in S1 File). Scholars have challenged this characterization, stating there is no convincing evidence to support the scenario of deforestation caused by anthropogenic activities [14] It has been the goal of our research to provide fresh insights into the sustainability of land-use practices in Chaco Canyon during the Ancestral Puebloan occupation. We add new data that reveal measurable changes in the pinyon juniper woodlands (PJW) that occurred before 600 BC when the food procurement system was transitioning from hunting and gathering to agricultural production This shift in resource procurement enhanced the ability of the Ancestral Puebloans to sustain larger populations for several centuries, but by AD 1075–1100 it came at a cost of a major reduction of tree density in the local woodlands

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