Sixteenth-century soil carbon sequestration rates based on Mexican land-grant documents

Abstract

A significant gap in our understanding of global change involves the linkages between historical land-use and land-cover change (LULCC), Holocene terrestrial carbon (C) pool fluxes, and climate change. To address that research problem, this method uses land grants for sheep ranches awarded in early colonial (1521–1620 CE) Mexico to quantify the amount of land converted from cropland to pastureland. Soil is the largest terrestrial C pool, and converting cropland to pastureland significantly increases soil C sequestration rates, thereby reducing atmospheric C. The land grants and associated archival documents contain location-specific information about soils, vegetation, hydrology, and other variables that make it possible to map the ranches in a Geographic Information System (GIS) and quantify LULCCs and terrestrial C pools over time and space. The results demonstrate the utility of such archival documents to research on Holocene global change, indicate that LULCC during Mexico’s colonial period increased the region’s soil C sequestration rate, and confirm previous research that has suggested that transformations associated with European colonization of the Americas acted as an anthropogenic contributor to the period of moderate cooling known as the ‘Little Ice Age’ (1550–1850 CE).