Reconstructing the Rio Bravo watershed : over 2000 years of wetland management in northwest Belize

Humans have depended upon wetlands throughout history, yet rapid development and industrial agriculture have driven a drastic decrease of these valuable ecosystems in recent decades. While the Anthropocene is generally thought of as a modern phenomenon, humans have been intensely modifying the Earth for thousands of years. In Northwest Belize, the landscape provides a unique lens to study wetland management and agriculture on multiple time scales: the ancient Maya and the modern. The Maya occupied the region for thousands of years, practicing intensive wetland agriculture from the Early Preclassic through the Post Classic periods (~3000-1000 BP), when the region experienced rapid population decline and abandonment of urban centers. These forests have remained minimally disturbed by humans until recent decades with the spread of industrial agriculture. In this dissertation, I aim to understand how the ancient Maya farmed these wetlands in the past and the implications for sustainable wetland management as modern farmers clear-cut and drain wetlands. In the first chapter, I use NASA’s Landsat satellite data archive and machine learning to map the spread of agriculture and loss of wetlands and forests from 1985 through 2015. In the second chapter, I compare remotely sensed data sources that have been used for mapping ancient Maya wetland agriculture from the 1970’s to the present. As LiDAR proves the most useful for mapping the ancient landscape, we also compare LiDAR-derived products for identifying ancient Maya canals and demonstrate the use of machine learning to accelerate the mapping of these systems. We apply this technique to the newly rediscovered ancient Maya wetland fields of the Central Rio Bravo (CRB), revealing over 7 km2 of raised fields. In the third chapter, I use field surveys, excavations, stratigraphy, radiocarbon dating, elemental analysis, and stable carbon isotopes to reconstruct the chronology of the CRB wetlands and ancient impacts. The extent, longevity, and late expansion of the wetland system reflects the importance of wetland agriculture to this region, the role of wetlands as refuge during droughts, wetlands as a focus of Postclassic continuation in a time of abandonment, and the potential of this method for sustainable wetland management.