A critical evaluation of soil salinization, waterlogging, and agricultural productive capacity in Hohokam irrigation of the Phoenix Basin, Arizona, USA.

Abstract

A causal link between environmental degradation and societal collapse has captivated the imagination of generations of archaeologists, historians, and the public. At its core, it is believed that the agricultural aspirations of societies outstrip what the environment can offer. The Hohokam, who farmed the Phoenix Basin of Arizona, USA, for nearly a millennium (AD 475-1450), have been repeatedly used as an exemplar of incongruence between the environment and agricultural practices leading to crop failures and ultimately societal collapse. Contributing to the collapse narrative is crop failures that spread across the lower Salt River Valley during the late 1800s. Unacknowledged by collapse narratives is that unproductive fields were brought back to life at the start of the twentieth century with techniques not beyond the capability of the Hohokam. Hohokam farmers and their descendants maintained and prospered in the valley for more than a millennium, so the assumed unidirectionality toward degraded productive capacity warrants examination. In this article, five lines of evidence are used to assess the relationships among soil salinization, waterlogging, and agricultural productive capacity. The multistep approach reveals that available evidence fails to substantiate soil salinization and waterlogging as primary catalysts in the decline of Hohokam irrigation. As such, establishing causality between environmental factors and societal decline in the past requires multiple lines of evidence producing contextually detailed syntheses, rather than simple models.