Impacts of Megadroughts on North American Native Cultures and Civilizations

The existence of western North American multi-decadal droughts, and even centennial-length megadroughts, and their impacts on Native cultures and civilizations are being increasingly appreciated. These exceptionally severe and long-lasting droughts have barely been experienced by European settler cultures in North America, but have been fully experienced by Native agricultural communities which have been heavily impacted by them. The historical, archeological and paleo-climate proxy records of many researchers document at least three major megadroughts in the past millennium: a Southwest-centered Puebloan drought in the second half of the 1200s, a Mississippian drought spanning much of the 1300s and a 16^th century megadrought covering much of western North America. The Puebloan drought has been conjectured to have caused abandonment of Ancestral Pueblo communities on the Colorado Plateau, the Mississippian drought is contemporaneous with the final stages of many Mound-Builder sites of the Mississippi Valley, and the 16^th century drought had historically documented effects on Puebloan cultures and the Mexican civilizations. In this talk, evidence of the expansion of the Mississippian drought in its full severity into central Minnesota is presented from annually-laminated sediment cores from Lake Mina, Minnesota, and its possible effects on the maize-farming communities of the Upper Missouri Valley are discussed. Multi-decadal droughts have long been recognized in northern Great Plains tree-ring records; here are also presented our research group’s recent work associating many of these droughts in both the instrumental and tree-ring records to North Pacific Sea Surface Temperatures or Pacific Decadal Oscillation (PDO) phase and the first detection of the Mississippian and the 16^th century megadroughts in the North and South Saskatchewan River Basins.