Global Change, Mesoamerican wetland farming, and the Early Anthropocene

Abstract:

To assess the onset of the Anthropocene we must establish the extent, intensity, and chronology of human impacts on landscapes and connect these impacts to global change through greenhouse gas (GHG) fluxes. Landscapes interact with GHGs and these have global climate implications. Lidar, capable of precisely mapping through forest gaps, has revolutionized our ability to characterize and quantify humanized landscapes. But in many cases, lidar is only as good as its accompanying ground verification. Here we forge these together to compare a mature literature on wetland contributions to the Early Anthropocene in Asia through methane from paddy rice agriculture with the growing literature on a large area of wetland agriculture in the Americas, focusing on the newest discoveries in Central America. Several studies have linked the ~20 ppm rise in atmospheric CO₂ from ~7000-1000 BP with deforestation for global farming; the 100 ppb rise in CH₄ from ~5000-1000 BP with wetland farming; and the 7-10 ppm decline in CO₂ in the sixteenth century CE with reforestation and population collapses of the Americas after the European Conquest. We synthesize the evidence for the onset, duration, extent,and impacts of wetland agriculture in Mesoamerica to compare their impacts on GHGs, and, thus, their contributions to global impacts on climate. This Early Anthropocene connects to the current Anthropocene because drainage and deforestation, now for industrial wetland rice agriculture, are changing these ancient field systems by again adding to Greenhouse gases and expunging their record of human/ landscape interactions.