Tropical wetlands are important ecosystems with complex interactions between their soils and water, but little is known about how humans further affect and alter them over long time periods. This project will study northern Belize's wetlands to test models of wetland formation and long-term human-environmental interactions in the Maya Lowlands. Most previous Maya research has focused on risks such as recurrent droughts but rising water tables and water quality may prove to be comparable but insidious risks. This is a case of humans forced to adapt to rising water tables of extremely hard water. The main goals of this project are to determine the timing and processes of perennial wetland formation across a range of environments in the northern Belize coastal plain; to discern the underestimated role of water chemistry in landscape formation in this tropical region; and to establish the types and ranges of human adaptations to wetland formation, linking sites of previous research, including Blue Creek and Pulltrouser Swamp. The underlying questions come from both natural and social science. The project is testing six possible hypotheses to explain large-scale landscape aggradation and formation during the Holocene across the Belize coastal plain. This project will test the landscape development models by studying seven known ancient Maya wetland field sites that span from the Blue Creek research sites, through a zone that received no previous research on stratigraphy and dating, to the zone of research done several decades ago. This project will test these models with multidisciplinary research at two scales: intensive excavation across canals and fields and extensive vibracoring to determine wetland field extents. In each site, the project will study the lines of evidence that explain landscape formation and human interaction: stratigraphy, dating methods, soil morphology, sediment chemistry, ecofacts (pollen, diatoms), and artifacts. This project will also conduct water chemical analysis across this zone because of its key role in wetlands and its little-understood role in Maya Civilization.
This study will provide a case of an important Pre-Columbian society's land use responses in the face of natural sea level and water table rise; it will help flesh out the mechanisms of landscape formation over a little understood, large tropical wetland region; and it will help determine the Holocene rates and processes of tropical wetland formation when these bio-diverse regions again face sea level rise and other widespread threats. The study also provides basic soil and water chemistry data to a developing region, and these baseline parameters can help scientists and resource managers judge many aspects of environmental change such as wetland ecosystem functions. This project will provide graduate and undergraduate students experience in international field science and laboratory research. The project will include and train many from local communities during and between the field seasons. The project will disseminate findings on wetland formation and Maya cultural ecology to international conferences, peer reviewed journals, to students, and more widely through websites and the mass media. The infrastructure of science will be improved through both the multidisciplinary approach and the international nature of this research.
People for millennia have manipulated wetlands in many ways to gain resources. One such manipulation was to modify wetlands for different types of agriculture either in response to changing environments or to expand onto new lands. The history of these manipulations is important because it shows how humans have reclaimed non-arable lands and adapted to changing conditions, how diverse cultures responded to opportunities and risks differently, and how they interacted positively or negatively with their environments. This project studies the history of wetlands in Belize, Central America, and it has real implications for the modern and future world of dynamic and changing climates, sea levels, ecosystems, and human property. Studying wetland fields requires understanding them in multiple dimensions: surficial, stratigraphic, and diachronic expressions. Each of these are complicated puzzles that require different methods. The surficial component is the size, length, and directionality of canals, fields, and other waterways compared with a determination of what is natural versus human made. Northern Belize has large areas of web-like and rectilinear patterns that appear to be canal systems. The stratigraphic is the way sediment lays and folds around lower and adjacent sediment through canals and fields, and the diachronic is how these strata have formed over time by humans and natural processes based on radiocarbon dates and proxies of human use and environmental change such as pollen, phytoliths, charcoal, and soil and water chemistry. These proxies tell us that maize agriculture started here before 5000 years ago. We have studied the surficial with remote sensing (satellite imagery and 1000s of air photos) and multiple surface surveys to understand canal and field dimensions and the wider extent of wetland systems. We have studied stratigraphy with twenty new excavations and many more new coring sites in suspect fields and natural wetland sites over northern Belize, and we have scores of new radiocarbon dates and proxy evidence to date and characterize them. We are identifying which wetland field patterns are natural ones and which are indeed anthropogenic, and we are improving our estimate of the areal extent and thus importance of wetland agriculture. Using all of these methods, we have discovered new wetland fields in Belize at Sierra de Agua, Chawak, BOP, Sayap Ha, and Lamanai (Figure) within the broad background of human induced landscape change. We have also identified a whole suite of highly probable sites based on remote sensing, which we are in the process of studying based on coring and excavations from tools made possible by this NSF project. Each of these sites has multiple lines of evidence for Maya construction and use as wetland fields in the Classic Period, especially from 1500 to 1100 years ago. We do not discount earlier uses of the fields, but all of our direct evidence is for Classic Period use in terms of pollen from corn and cassava, from increased charcoal, from organic chemical residues from completely different plants from the natural plants in the area today, and from the dates in canals and activity areas. The expansion onto these wetlands in the Late Classic also occurred in a gradual and piecemeal process in some sites but a preplanned and systematic process in at least one area, though remote sensing suggests more. We have also studied natural features in these landscapes that produce webs and rectilinear patterns like fields and canals. A previous model posited an explanation of gypsic domes or laccoliths to explain these patterns, because much of the area has water tables with high amounts of calcium and sulfate, which would precipitate as gypsum in the dry season as water evaporates into the atmosphere and gypsum crystalizes into the soil. Hence, we studied sites with a continuum of water characteristics from the highest dissolved loads and high amounts of sulfur and calcium to lower amounts of each. We did find gypsic doming in some areas, but these tended to have only small ‘fields’ and ‘canals’ on the high end of the gypsum-rich water spectrum. We interpret most others to be Classic period Maya canal and field systems to grow a variety of crops from corn to cassava and to tree crops like avocados, fruits, and palms. Their expansion across wetlands correlates with the greatest population and agriculture expansion in Maya history as well as a period most scholars believe was becoming both dryer, in terms of climate, and wetter, in terms of sea level rise, inundating formerly dry fields. Our next steps will be to further distinguish the extent and uses of wetland fields and thus their importance and to differentiate the three great motivations for construction: population expansion, drying, and inundation. These are factors at least as important to wetland use and destruction today as they were a millennium ago, especially in these tropical wetlands under constant threat of destruction.
