Spanish colonization triggered 17th-century landscape dust regime shift in the Southwestern United States

Abstract

In the Southwest United States, increased dust mass accumulation rates (DMAR) have been linked to land use changes driven by American westward expansion in the 19th century. Here we present a new, high-resolution dust accumulation record reconstructed from varved sediments in Columbine Lake in the San Juan Mountains, Colorado. By examining DMAR with a substantially more accurate age model and at higher temporal resolution, we find that dust increased dramatically in the 17th century, with robust change point analysis identifying 1667 CE (95% confidence interval: 1640–1740 CE) as the onset of sustained landscape disruption. This timing coincides with Spanish colonial settlement rather than American expansion in the 19th century, reaching peak DMAR values of 30 g/m²/yr (interquartile range: 15–81 g/m²/yr), the highest in the 3,400-year record. Combined with historical evidence of Spanish colonization, our findings suggest that the introduction of European livestock and farming practices in the Four Corners region triggered lasting changes in landscape stability. This change demonstrates that colonial extraction destroyed the pre-existing decoupling between dust deposition and drought, a relationship that defined the pre-colonial dust regime, providing a critical insight for understanding modern landscape vulnerability.

Teaser

A new high-resolution varve dust accumulation record for the past 3400 years reveals that Spanish colonial activities in the 17th century, not 19th century American settlement, initiated sustained landscape disturbance and elevated dust levels in the Southwest.