LONG-TERM HUMAN IMPACT ON A NEOTROPICAL FLUVIAL SYSTEM IN THE BELIZE-GUATEMALA TRANSBOUNDARY AREA

Humans have played a significant role in the geomorphic evolution of the Belize River Valley in western Belize over the past 4,000 years, and this anthropogenic landscape still influences land use and flooding regimes today. Using LiDAR and GIS, fieldwork and lab analyses, we have quantified to what extent ancient Maya construction and agriculture affected the sediment budget thereby influencing geomorphic evolution of the river system and flood frequency. Soil geochemistry and radiocarbon dating have identified several 1-4,000-year-old horizons that are high in phosphorus, calcium, and potassium. These horizons are also characterized by clay-sized particles, abundant organic matter and elevated magnetic susceptibility values. We have found that these buried soils are often overlain by a deposit of coarse, non-local sandy material that was transported from the Maya Mountains some 50 km away. Our results suggest that Maya activity caused changes to the Belize River’s sediment budget, thus contributing to the geomorphic evolution of the fluvial landscape. Further dating and characterization of buried soils and strata in these systems should build our record of long-term fluvial change and allow us to assess the chronology for pedogenesis in the tropical river basin. Quantifying the role humans play in landscape change could offer important insight into modern environmental management and conservation efforts, including flood planning, which is particularly relevant in the rapidly-developing, increasingly populated, tropics of Central America.