Human securities, sustainability, and migration in the ancient U.S. Southwest and Mexican Northwest

In the U.S. Southwest and Mexican Northwest region, arid-lands agriculturalists practiced sedentary agriculture for at least four thousand years. People developed diverse lifeways and a repertoire of successful dryland strategies that resemble those of some small-scale agriculturalists today. A multi-millennial trajectory of variable population growth ended during the early 1300s CE and by the late 1400s population levels in the region declined by about one-half. Here we show, through a meta-analysis of sub-regional archaeological studies, the spatial distribution, intensity, and variation in social and environmental conditions throughout the region prior to depopulation. We also find that as these conditions, identified as human insecurities by the UN Development Programme, worsened, the speed of depopulation increased. Although these conditions have been documented within some sub-regions, the aggregate weight and distribution of these insecurities throughout the Southwest/Northwest region were previously unrecognized. Population decline was not the result of a single disturbance, such as drought, to the regional system; it was a spatially patterned, multi-generational decline in human security. Results support the UN's emphasis on increasing human security as a pathway toward sustainable development and lessening forced migration. Through these results and the approach demonstrated here, we aim to stimulate collaborations between archaeologists and others in service of modern sustainability planning.