Wetland Farming and the Early Anthropocene: Globally Upscaling from the Maya Lowlands with LiDAR and Multiproxy Verification

Abstract

Of multiple ways to assess the geography of the early Anthropocene, three ongoing efforts are establishing the extent, intensity, and chronology of human impacts on landscapes and connecting 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. In many cases, though, LiDAR is only as good as its accompanying ground verification. This article forges 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 to 1000 BP with deforestation for global farming; the 100 ppb rise in CH4 from ∼5000 to 1000 BP with wetland farming; and the 7 to 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, and impacts of wetland agriculture in the Maya Lowlands of Mesoamerica to compare their impacts on GHGs and, thus, their contributions to global impacts on climate. This article builds from three decades of studying neotropical humanized landscapes and wetland agroecosystems and more recent quantification from ground-verified LiDAR imagery and synthesizes this growing research and the challenges ahead to gauge the early Anthropocene.