North American Tree Rings, Climatic Extremes, and Social Disasters

Abstract

Tree-ring reconstructed climatic extremes contemporaneous with severe socioeconomic impacts can be identified in the modern, colonial, and precolonial eras. These events include the 1950s, Dust Bowl, mid- and late-nineteenth century Great Plains droughts, El Año del Hambre, and the seventeenth and sixteenth century droughts among the English and Spanish colonies. The new tree-ring reconstructions confirm the severe, sustained Great Drought over the Colorado Plateau in the late thirteenth century identified by A.E. Douglass and document its spatial impact across the cultural heartland of the Anasazi. The available tree-ring data also indicate a succession of severe droughts over the western United States during the Terminal Classic Period in Mesoamerica, but these droughts are located far from the centers of Mesoamerican culture and their extension into central Mexico needs to be confirmed with the new suite of millennium-long tree-ring chronologies now under development in the region. The only clear connections between climate extremes and human impacts are found during the period of written history, including the prehispanic Aztec era where codices describe the drought of One Rabbit in Mexico and other precolonial droughts. The link between reconstructed climate and societies in the prehistoric era may never be made irrefutably, but testing these hypotheses with improved climate reconstructions, better archaeological data, and modeling experiments to explore the range of potential social response have to be central goals of archaeology and high-resolution paleoclimatology.